Table of Contents
The MySQL™ software delivers a very fast, multithreaded, multi-user, and robust SQL (Structured Query Language) database server. MySQL Server is intended for mission-critical, heavy-load production systems as well as for embedding into mass-deployed software. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. MySQL is a trademark of Oracle Corporation and/or its affiliates, and shall not be used by Customer without Oracle's express written authorization. Other names may be trademarks of their respective owners.
The MySQL software is Dual Licensed. Users can choose to use the MySQL software as an Open Source product under the terms of the GNU General Public License (http://www.fsf.org/licenses/) or can purchase a standard commercial license from Oracle. See http://www.mysql.com/company/legal/licensing/ for more information on our licensing policies.
The following list describes some sections of particular interest in this manual:
For a discussion of MySQL Database Server capabilities, see Section 1.3.2, “The Main Features of MySQL”.
For an overview of new MySQL features, see Section 1.4, “What Is New in MySQL 8.0”. For information about the changes in each version, see the Release Notes.
For installation instructions, see Chapter 2, Installing and Upgrading MySQL. For information about upgrading MySQL, see Section 2.11.1, “Upgrading MySQL”.
For a tutorial introduction to the MySQL Database Server, see Chapter 3, Tutorial.
For information about configuring and administering MySQL Server, see Chapter 5, MySQL Server Administration.
For information about security in MySQL, see Chapter 6, Security.
For information about setting up replication servers, see Chapter 17, Replication.
For information about MySQL Enterprise, the commercial MySQL release with advanced features and management tools, see Chapter 30, MySQL Enterprise Edition.
For answers to a number of questions that are often asked concerning the MySQL Database Server and its capabilities, see Appendix A, MySQL 8.0 Frequently Asked Questions.
For a history of new features and bug fixes, see the Release Notes.
To report problems or bugs, please use the instructions at
Section 1.7, “How to Report Bugs or Problems”. If you find a sensitive security
bug in MySQL Server, please let us know immediately by sending an
email message to <[email protected]>. Exception:
Support customers should report all problems, including security
bugs, to Oracle Support.
This is the Reference Manual for the MySQL Database System,
version 8.0, through release 8.0.16.
Differences between minor versions of MySQL 8.0 are
noted in the present text with reference to release numbers
(8.0.x). For license
information, see the Legal
Notices.
This manual is not intended for use with older versions of the MySQL software due to the many functional and other differences between MySQL 8.0 and previous versions. If you are using an earlier release of the MySQL software, please refer to the appropriate manual. For example, MySQL 5.7 Reference Manual covers the 5.7 series of MySQL software releases.
Because this manual serves as a reference, it does not provide general instruction on SQL or relational database concepts. It also does not teach you how to use your operating system or command-line interpreter.
The MySQL Database Software is under constant development, and the Reference Manual is updated frequently as well. The most recent version of the manual is available online in searchable form at https://dev.mysql.com/doc/. Other formats also are available there, including HTML, PDF, and EPUB versions.
The Reference Manual source files are written in DocBook XML format. The HTML version and other formats are produced automatically, primarily using the DocBook XSL stylesheets. For information about DocBook, see http://docbook.org/
The source code for MySQL itself contains internal documentation written using Doxygen. The generated Doxygen content is available at https://dev.mysql.com/doc/dev/mysql-server/latest/. It is also possible to generate this content locally from a MySQL source distribution using the instructions at Section 2.9.7, “Generating MySQL Doxygen Documentation Content”.
If you have questions about using MySQL, you can ask them using our mailing lists or forums. See Section 1.6.2, “MySQL Mailing Lists”, and Section 1.6.3, “MySQL Community Support at the MySQL Forums”. If you have suggestions concerning additions or corrections to the manual itself, please send them to the http://www.mysql.com/company/contact/.
This manual was originally written by David Axmark and Michael “Monty” Widenius. It is maintained by the MySQL Documentation Team, consisting of Chris Cole, Paul DuBois, Margaret Fisher, Edward Gilmore, Stefan Hinz, David Moss, Philip Olson, Daniel Price, Daniel So, and Jon Stephens.
This manual uses certain typographical conventions:
Text in this style is used for SQL
statements; database, table, and column names; program listings
and source code; and environment variables. Example: “To
reload the grant tables, use the FLUSH
PRIVILEGES statement.”
Text in this style indicates input that
you type in examples.
Text in this style indicates the names of executable programs and scripts, examples being mysql (the MySQL command-line client program) and mysqld (the MySQL server executable).
Text in this style is used for
variable input for which you should substitute a value of your
own choosing.
Text in this style is used for emphasis.
Text in this style is used in table headings and to convey especially strong emphasis.
Text in this style is used to indicate a
program option that affects how the program is executed, or that
supplies information that is needed for the program to function
in a certain way. Example: “The
--host option (short form -h)
tells the mysql client program the hostname
or IP address of the MySQL server that it should connect
to”.
File names and directory names are written like this: “The
global my.cnf file is located in the
/etc directory.”
Character sequences are written like this: “To specify a
wildcard, use the ‘%’
character.”
When commands are shown that are meant to be executed from within a
particular program, the prompt shown preceding the command indicates
which command to use. For example, shell>
indicates a command that you execute from your login shell,
root-shell> is similar but should be executed
as root, and mysql>
indicates a statement that you execute from the
mysql client program:
shell>type a shell command hereroot-shell>type a shell command asmysql>rootheretype a mysql statement here
In some areas different systems may be distinguished from each other
to show that commands should be executed in two different
environments. For example, while working with replication the
commands might be prefixed with master and
slave:
master>type a mysql command on the replication master hereslave>type a mysql command on the replication slave here
The “shell” is your command interpreter. On Unix, this is typically a program such as sh, csh, or bash. On Windows, the equivalent program is command.com or cmd.exe, typically run in a console window.
When you enter a command or statement shown in an example, do not type the prompt shown in the example.
Database, table, and column names must often be substituted into
statements. To indicate that such substitution is necessary, this
manual uses db_name,
tbl_name, and
col_name. For example, you might see a
statement like this:
mysql> SELECT col_name FROM db_name.tbl_name;
This means that if you were to enter a similar statement, you would supply your own database, table, and column names, perhaps like this:
mysql> SELECT author_name FROM biblio_db.author_list;
SQL keywords are not case-sensitive and may be written in any lettercase. This manual uses uppercase.
In syntax descriptions, square brackets
(“[” and
“]”) indicate optional words or
clauses. For example, in the following statement, IF
EXISTS is optional:
DROP TABLE [IF EXISTS] tbl_name
When a syntax element consists of a number of alternatives, the
alternatives are separated by vertical bars
(“|”). When one member from a set of
choices may be chosen, the alternatives are
listed within square brackets (“[”
and “]”):
TRIM([[BOTH | LEADING | TRAILING] [remstr] FROM]str)
When one member from a set of choices must be
chosen, the alternatives are listed within braces
(“{” and
“}”):
{DESCRIBE | DESC} tbl_name [col_name | wild]
An ellipsis (...) indicates the omission of a
section of a statement, typically to provide a shorter version of
more complex syntax. For example,
SELECT ... INTO
OUTFILE is shorthand for the form of
SELECT statement that has an
INTO OUTFILE clause following other parts of the
statement.
An ellipsis can also indicate that the preceding syntax element of a
statement may be repeated. In the following example, multiple
reset_option values may be given, with
each of those after the first preceded by commas:
RESETreset_option[,reset_option] ...
Commands for setting shell variables are shown using Bourne shell
syntax. For example, the sequence to set the CC
environment variable and run the configure
command looks like this in Bourne shell syntax:
shell> CC=gcc ./configure
If you are using csh or tcsh, you must issue commands somewhat differently:
shell>setenv CC gccshell>./configure
MySQL, the most popular Open Source SQL database management system, is developed, distributed, and supported by Oracle Corporation.
The MySQL website (http://www.mysql.com/) provides the latest information about MySQL software.
MySQL is a database management system.
A database is a structured collection of data. It may be anything from a simple shopping list to a picture gallery or the vast amounts of information in a corporate network. To add, access, and process data stored in a computer database, you need a database management system such as MySQL Server. Since computers are very good at handling large amounts of data, database management systems play a central role in computing, as standalone utilities, or as parts of other applications.
MySQL databases are relational.
A relational database stores data in separate tables rather than putting all the data in one big storeroom. The database structures are organized into physical files optimized for speed. The logical model, with objects such as databases, tables, views, rows, and columns, offers a flexible programming environment. You set up rules governing the relationships between different data fields, such as one-to-one, one-to-many, unique, required or optional, and “pointers” between different tables. The database enforces these rules, so that with a well-designed database, your application never sees inconsistent, duplicate, orphan, out-of-date, or missing data.
The SQL part of “MySQL” stands for “Structured Query Language”. SQL is the most common standardized language used to access databases. Depending on your programming environment, you might enter SQL directly (for example, to generate reports), embed SQL statements into code written in another language, or use a language-specific API that hides the SQL syntax.
SQL is defined by the ANSI/ISO SQL Standard. The SQL standard has been evolving since 1986 and several versions exist. In this manual, “SQL-92” refers to the standard released in 1992, “SQL:1999” refers to the standard released in 1999, and “SQL:2003” refers to the current version of the standard. We use the phrase “the SQL standard” to mean the current version of the SQL Standard at any time.
MySQL software is Open Source.
Open Source means that it is possible for anyone to use and modify the software. Anybody can download the MySQL software from the Internet and use it without paying anything. If you wish, you may study the source code and change it to suit your needs. The MySQL software uses the GPL (GNU General Public License), http://www.fsf.org/licenses/, to define what you may and may not do with the software in different situations. If you feel uncomfortable with the GPL or need to embed MySQL code into a commercial application, you can buy a commercially licensed version from us. See the MySQL Licensing Overview for more information (http://www.mysql.com/company/legal/licensing/).
The MySQL Database Server is very fast, reliable, scalable, and easy to use.
If that is what you are looking for, you should give it a try. MySQL Server can run comfortably on a desktop or laptop, alongside your other applications, web servers, and so on, requiring little or no attention. If you dedicate an entire machine to MySQL, you can adjust the settings to take advantage of all the memory, CPU power, and I/O capacity available. MySQL can also scale up to clusters of machines, networked together.
MySQL Server was originally developed to handle large databases much faster than existing solutions and has been successfully used in highly demanding production environments for several years. Although under constant development, MySQL Server today offers a rich and useful set of functions. Its connectivity, speed, and security make MySQL Server highly suited for accessing databases on the Internet.
MySQL Server works in client/server or embedded systems.
The MySQL Database Software is a client/server system that consists of a multithreaded SQL server that supports different back ends, several different client programs and libraries, administrative tools, and a wide range of application programming interfaces (APIs).
We also provide MySQL Server as an embedded multithreaded library that you can link into your application to get a smaller, faster, easier-to-manage standalone product.
A large amount of contributed MySQL software is available.
MySQL Server has a practical set of features developed in close cooperation with our users. It is very likely that your favorite application or language supports the MySQL Database Server.
The official way to pronounce “MySQL” is “My Ess Que Ell” (not “my sequel”), but we do not mind if you pronounce it as “my sequel” or in some other localized way.
This section describes some of the important characteristics of the MySQL Database Software. In most respects, the roadmap applies to all versions of MySQL. For information about features as they are introduced into MySQL on a series-specific basis, see the “In a Nutshell” section of the appropriate Manual:
MySQL 8.0: Section 1.4, “What Is New in MySQL 8.0”
MySQL 5.7: What Is New in MySQL 5.7
MySQL 5.6: What Is New in MySQL 5.6
MySQL 5.5: What Is New in MySQL 5.5
Written in C and C++.
Tested with a broad range of different compilers.
Works on many different platforms. See https://www.mysql.com/support/supportedplatforms/database.html.
For portability, uses CMake in MySQL 5.5 and up. Previous series use GNU Automake, Autoconf, and Libtool.
Tested with Purify (a commercial memory leakage detector) as well as with Valgrind, a GPL tool (http://developer.kde.org/~sewardj/).
Uses multi-layered server design with independent modules.
Designed to be fully multithreaded using kernel threads, to easily use multiple CPUs if they are available.
Provides transactional and nontransactional storage engines.
Uses very fast B-tree disk tables (MyISAM)
with index compression.
Designed to make it relatively easy to add other storage engines. This is useful if you want to provide an SQL interface for an in-house database.
Uses a very fast thread-based memory allocation system.
Executes very fast joins using an optimized nested-loop join.
Implements in-memory hash tables, which are used as temporary tables.
Implements SQL functions using a highly optimized class library that should be as fast as possible. Usually there is no memory allocation at all after query initialization.
Provides the server as a separate program for use in a client/server networked environment, and as a library that can be embedded (linked) into standalone applications. Such applications can be used in isolation or in environments where no network is available.
Full operator and function support in the
SELECT list and
WHERE clause of queries. For example:
mysql>SELECT CONCAT(first_name, ' ', last_name)->FROM citizen->WHERE income/dependents > 10000 AND age > 30;
Full support for SQL GROUP BY and
ORDER BY clauses. Support for group
functions (COUNT(),
AVG(),
STD(),
SUM(),
MAX(),
MIN(), and
GROUP_CONCAT()).
Support for LEFT OUTER JOIN and
RIGHT OUTER JOIN with both standard SQL and
ODBC syntax.
Support for aliases on tables and columns as required by standard SQL.
Support for DELETE,
INSERT,
REPLACE, and
UPDATE to return the number of
rows that were changed (affected), or to return the number of
rows matched instead by setting a flag when connecting to the
server.
Support for MySQL-specific SHOW
statements that retrieve information about databases, storage
engines, tables, and indexes. Support for the
INFORMATION_SCHEMA database, implemented
according to standard SQL.
An EXPLAIN statement to show
how the optimizer resolves a query.
Independence of function names from table or column names. For
example, ABS is a valid column name. The
only restriction is that for a function call, no spaces are
permitted between the function name and the
“(” that follows it. See
Section 9.3, “Keywords and Reserved Words”.
You can refer to tables from different databases in the same statement.
A privilege and password system that is very flexible and secure, and that enables host-based verification.
Password security by encryption of all password traffic when you connect to a server.
Support for large databases. We use MySQL Server with databases that contain 50 million records. We also know of users who use MySQL Server with 200,000 tables and about 5,000,000,000 rows.
Support for up to 64 indexes per table. Each index may consist
of 1 to 16 columns or parts of columns. The maximum index
width for InnoDB tables is either
767 bytes or 3072 bytes. See
Section 15.6.1.6, “Limits on InnoDB Tables”. The maximum index width
for MyISAM tables is 1000 bytes.
See Section 16.2, “The MyISAM Storage Engine”. An index may use
a prefix of a column for CHAR,
VARCHAR,
BLOB, or
TEXT column types.
Clients can connect to MySQL Server using several protocols:
Clients can connect using TCP/IP sockets on any platform.
On Windows systems, clients can connect using named pipes
if the server is started with the
--enable-named-pipe option.
Windows servers also support shared-memory connections if
started with the
--shared-memory option.
Clients can connect through shared memory by using the
--protocol=memory option.
On Unix systems, clients can connect using Unix domain socket files.
MySQL client programs can be written in many languages. A client library written in C is available for clients written in C or C++, or for any language that provides C bindings.
APIs for C, C++, Eiffel, Java, Perl, PHP, Python, Ruby, and Tcl are available, enabling MySQL clients to be written in many languages. See Chapter 28, Connectors and APIs.
The Connector/ODBC (MyODBC) interface provides MySQL support for client programs that use ODBC (Open Database Connectivity) connections. For example, you can use MS Access to connect to your MySQL server. Clients can be run on Windows or Unix. Connector/ODBC source is available. All ODBC 2.5 functions are supported, as are many others. See MySQL Connector/ODBC Developer Guide.
The Connector/J interface provides MySQL support for Java client programs that use JDBC connections. Clients can be run on Windows or Unix. Connector/J source is available. See MySQL Connector/J 5.1 Developer Guide.
MySQL Connector/NET enables developers to easily create .NET applications that require secure, high-performance data connectivity with MySQL. It implements the required ADO.NET interfaces and integrates into ADO.NET aware tools. Developers can build applications using their choice of .NET languages. MySQL Connector/NET is a fully managed ADO.NET driver written in 100% pure C#. See MySQL Connector/NET Developer Guide.
The server can provide error messages to clients in many languages. See Section 10.11, “Setting the Error Message Language”.
Full support for several different character sets, including
latin1 (cp1252), german,
big5, ujis, several
Unicode character sets, and more. For example, the
Scandinavian characters “å”,
“ä” and
“ö” are permitted in table
and column names.
All data is saved in the chosen character set.
Sorting and comparisons are done according to the default character set and collation. is possible to change this when the MySQL server is started (see Section 10.3.2, “Server Character Set and Collation”). To see an example of very advanced sorting, look at the Czech sorting code. MySQL Server supports many different character sets that can be specified at compile time and runtime.
The server time zone can be changed dynamically, and individual clients can specify their own time zone. See Section 5.1.13, “MySQL Server Time Zone Support”.
MySQL includes several client and utility programs. These include both command-line programs such as mysqldump and mysqladmin, and graphical programs such as MySQL Workbench.
MySQL Server has built-in support for SQL statements to check,
optimize, and repair tables. These statements are available
from the command line through the
mysqlcheck client. MySQL also includes
myisamchk, a very fast command-line utility
for performing these operations on MyISAM
tables. See Chapter 4, MySQL Programs.
MySQL programs can be invoked with the --help
or -? option to obtain online assistance.
We started out with the intention of using the
mSQL database system to connect to our tables
using our own fast low-level (ISAM) routines. However, after some
testing, we came to the conclusion that mSQL
was not fast enough or flexible enough for our needs. This
resulted in a new SQL interface to our database but with almost
the same API interface as mSQL. This API was
designed to enable third-party code that was written for use with
mSQL to be ported easily for use with MySQL.
MySQL is named after co-founder Monty Widenius's daughter, My.
The name of the MySQL Dolphin (our logo) is “Sakila,” which was chosen from a huge list of names suggested by users in our “Name the Dolphin” contest. The winning name was submitted by Ambrose Twebaze, an Open Source software developer from Swaziland, Africa. According to Ambrose, the feminine name Sakila has its roots in SiSwati, the local language of Swaziland. Sakila is also the name of a town in Arusha, Tanzania, near Ambrose's country of origin, Uganda.
This section summarizes what has been added to, deprecated in, and removed from MySQL 8.0. A companion section lists MySQL server options and variables that have been added, deprecated, or removed in MySQL 8.0. See Section 1.5, “Server and Status Variables and Options Added, Deprecated, or Removed in MySQL 8.0”.
The following features have been added to MySQL 8.0:
Data dictionary. MySQL now incorporates a transactional data dictionary that stores information about database objects. In previous MySQL releases, dictionary data was stored in metadata files and nontransactional tables. For more information, see Chapter 14, MySQL Data Dictionary.
Atomic Data Definition Statements (Atomic DDL). An atomic DDL statement combines the data dictionary updates, storage engine operations, and binary log writes associated with a DDL operation into a single, atomic transaction. For more information, see Section 13.1.1, “Atomic Data Definition Statement Support”.
Security and account management. These enhancements were added to improve security and enable greater DBA flexibility in account management:
The grant tables in the mysql system
database are now InnoDB
(transactional) tables. Previously, these were
MyISAM (nontransactional) tables. The
change of grant table storage engine underlies an
accompanying change to the behavior of
account-management statements. Previously, an
account-management statement (such as
CREATE USER or
DROP USER) that named
multiple users could succeed for some users and fail for
others. Now, each statement is transactional and either
succeeds for all named users or rolls back and has no
effect if any error occurs. The statement is written to
the binary log if it succeeds, but not if it fails; in
that case, rollback occurs and no changes are made. For
more information, see Section 13.1.1, “Atomic Data Definition Statement Support”.
A new caching_sha2_password
authentication plugin is available. Like the
sha256_password plugin,
caching_sha2_password implements
SHA-256 password hashing, but uses caching to address
latency issues at connect time. It also supports more
connection protocols and does not require linking
against OpenSSL for RSA key pair-based password-exchange
capabilities. See
Section 6.5.1.3, “Caching SHA-2 Pluggable Authentication”.
The caching_sha2_password and
sha256_password authentication
plugins provide more secure password encryption than the
mysql_native_password plugin, and
caching_sha2_password provides better
performance than sha256_password. Due
to these superior security and performance
characteristics of
caching_sha2_password, it is now the
preferred authentication plugin, and is also the default
authentication plugin rather than
mysql_native_password. For
information about the implications of this change of
default plugin for server operation and compatibility of
the server with clients and connectors, see
caching_sha2_password as the Preferred Authentication Plugin.
MySQL now supports roles, which are named collections of privileges. Roles can be created and dropped. Roles can have privileges granted to and revoked from them. Roles can be granted to and revoked from user accounts. The active applicable roles for an account can be selected from among those granted to the account, and can be changed during sessions for that account. For more information, see Section 6.3.4, “Using Roles”.
MySQL now maintains information about password history, enabling restrictions on reuse of previous passwords. DBAs can require that new passwords not be selected from previous passwords for some number of password changes or period of time. It is possible to establish password-reuse policy globally as well as on a per-account basis.
It is now possible to require that attempts to change account passwords be verified by specifying the current password to be replaced. This enables DBAs to prevent users from changing password without proving that they know the current password. It is possible to establish password-verification policy globally as well as on a per-account basis.
Accounts are now permitted to have dual passwords, which enables phased password changes to be performed seamlessly in complex multiple-server systems, without downtime.
These new capabilities provide DBAs more complete control over password management. For more information, see Section 6.3.8, “Password Management”.
MySQL now supports FIPS mode, if compiled using OpenSSL, and an OpenSSL library and FIPS Object Module are available at runtime. FIPS mode imposes conditions on cryptographic operations such as restrictions on acceptable encryption algorithms or requirements for longer key lengths. See Section 6.6, “FIPS Support”.
MySQL now sets the access control granted to clients on
the named pipe to the minimum necessary for successful
communication on Windows. Newer MySQL client software
can open named pipe connections without any additional
configuration. If older client software cannot be
upgraded immediately, the new
named_pipe_full_access_group
server system variable can be used to give a Windows
group the necessary permissions to open a named pipe
connection. Membership in the full-access group should
be restricted and temporary.
Resource management. MySQL now supports creation and management of resource groups, and permits assigning threads running within the server to particular groups so that threads execute according to the resources available to the group. Group attributes enable control over its resources, to enable or restrict resource consumption by threads in the group. DBAs can modify these attributes as appropriate for different workloads. Currently, CPU time is a manageable resource, represented by the concept of “virtual CPU” as a term that includes CPU cores, hyperthreads, hardware threads, and so forth. The server determines at startup how many virtual CPUs are available, and database administrators with appropriate privileges can associate these CPUs with resource groups and assign threads to groups. For more information, see Section 8.12.5, “Resource Groups”.
InnoDB enhancements.
These InnoDB enhancements were added:
The current maximum auto-increment counter value is written to the redo log each time the value changes, and saved to an engine-private system table on each checkpoint. These changes make the current maximum auto-increment counter value persistent across server restarts. Additionally:
A server restart no longer cancels the effect of the
AUTO_INCREMENT = N table option.
If you initialize the auto-increment counter to a
specific value, or if you alter the auto-increment
counter value to a larger value, the new value is
persisted across server restarts.
A server restart immediately following a
ROLLBACK
operation no longer results in the reuse of
auto-increment values that were allocated to the
rolled-back transaction.
If you modify an AUTO_INCREMENT
column value to a value larger than the current
maximum auto-increment value (in an
UPDATE operation, for
example), the new value is persisted, and subsequent
INSERT operations
allocate auto-increment values starting from the
new, larger value.
For more information, see Section 15.6.1.4, “AUTO_INCREMENT Handling in InnoDB”, and InnoDB AUTO_INCREMENT Counter Initialization.
When encountering index tree corruption,
InnoDB writes a corruption flag to
the redo log, which makes the corruption flag crash
safe. InnoDB also writes in-memory
corruption flag data to an engine-private system table
on each checkpoint. During recovery,
InnoDB reads corruption flags from
both locations and merges results before marking
in-memory table and index objects as corrupt.
The InnoDB
memcached plugin supports multiple
get operations (fetching multiple
key-value pairs in a single memcached
query) and range queries. See
Section 15.19.4, “InnoDB memcached Multiple get and Range Query Support”.
A new dynamic variables,
innodb_deadlock_detect,
may be used to disable deadlock detection. On high
concurrency systems, deadlock detection can cause a
slowdown when numerous threads wait for the same lock.
At times, it may be more efficient to disable deadlock
detection and rely on the
innodb_lock_wait_timeout
setting for transaction rollback when a deadlock occurs.
The new
INFORMATION_SCHEMA.INNODB_CACHED_INDEXES
table reports the number of index pages cached in the
InnoDB buffer pool for each index.
InnoDB temporary tables are now
created in the shared temporary tablespace,
ibtmp1.
The InnoDB
tablespace
encryption feature supports encryption of redo
log and undo log data. See
Redo Log Data Encryption,
and
Undo Log Data Encryption.
InnoDB supports
NOWAIT and SKIP
LOCKED options with SELECT ... FOR
SHARE and SELECT ... FOR
UPDATE locking read statements.
NOWAIT causes the statement to return
immediately if a requested row is locked by another
transaction. SKIP LOCKED removes
locked rows from the result set. See
Locking Read Concurrency with NOWAIT and SKIP LOCKED.
SELECT ... FOR SHARE replaces
SELECT ... LOCK IN SHARE MODE, but
LOCK IN SHARE MODE remains available
for backward compatibility. The statements are
equivalent. However, FOR UPDATE and
FOR SHARE support
NOWAIT, SKIP
LOCKED, and OF
options.
See Section 13.2.10, “SELECT Syntax”.
tbl_name
OF
applies
locking queries to named tables.
tbl_name
ADD PARTITION, DROP
PARTITION, COALESCE
PARTITION, REORGANIZE
PARTITION, and REBUILD
PARTITION ALTER
TABLE options are supported by native
partitioning in-place APIs and may be used with
ALGORITHM={COPY|INPLACE} and
LOCK clauses.
DROP PARTITION with
ALGORITHM=INPLACE deletes data stored
in the partition and drops the partition. However,
DROP PARTITION with
ALGORITHM=COPY or
old_alter_table=ON
rebuilds the partitioned table and attempts to move data
from the dropped partition to another partition with a
compatible PARTITION ... VALUES
definition. Data that cannot be moved to another
partition is deleted.
The InnoDB storage engine now uses
the MySQL data dictionary rather than its own storage
engine-specific data dictionary. For information about
the data dictionary, see
Chapter 14, MySQL Data Dictionary.
mysql system tables and data
dictionary tables are now created in a single
InnoDB tablespace file named
mysql.ibd in the MySQL data
directory. Previously, these tables were created in
individual InnoDB tablespace files in
the mysql database directory.
The following undo tablespace changes are introduced in MySQL 8.0:
By default, undo logs now reside in two undo tablespaces that are created when the MySQL instance is initialized. Undo logs are no longer created in the system tablespace.
As of MySQL 8.0.14, additional undo tablespaces can
be created in a chosen location at runtime using
CREATE
UNDO TABLESPACE syntax.
CREATE UNDO TABLESPACEtablespace_nameADD DATAFILE 'file_name.ibu';
Undo tablespaces created using
CREATE
UNDO TABLESPACE syntax can be dropped at
runtime using
DROP
UNDO TABLESPACE syntax.
DROP UNDO TABLESPACE tablespace_name;
ALTER
UNDO TABLESPACE syntax can be used to mark
an undo tablespace as active or inactive.
ALTER UNDO TABLESPACE tablespace_name SET {ACTIVE|INACTIVE};
A STATE column that shows the
state of a tablespace was added to the
INFORMATION_SCHEMA.INNODB_TABLESPACES
table. An undo tablespace must be in an
empty state before it can be
dropped.
The
innodb_undo_log_truncate
variable is enabled by default.
The
innodb_rollback_segments
variable defines the number of rollback segments per
undo tablespace. Previously,
innodb_rollback_segments
specified the total number of rollback segments for
the MySQL instance. This change increases the number
of rollback segments available for concurrent
transactions. More rollback segments increases the
likelihood that concurrent transactions use separate
rollback segments for undo logs, resulting in less
resource contention.
Default values for variables that affect buffer pool preflushing and flushing behavior were modified:
The
innodb_max_dirty_pages_pct_lwm
default value is now 10. The previous default value
of 0 disables buffer pool preflushing. A value of 10
enables preflushing when the percentage of dirty
pages in the buffer pool exceeds 10%. Enabling
preflushing improves performance consistency.
The
innodb_max_dirty_pages_pct
default value was increased from 75 to 90.
InnoDB attempts to flush data
from the buffer pool so that the percentage of dirty
pages does not exceed this value. The increased
default value permits a greater percentage of dirty
pages in the buffer pool.
The default
innodb_autoinc_lock_mode
setting is now 2 (interleaved). Interleaved lock mode
permits the execution of multi-row inserts in parallel,
which improves concurrency and scalability. The new
innodb_autoinc_lock_mode
default setting reflects the change from statement-based
replication to row based replication as the default
replication type in MySQL 5.7.
Statement-based replication requires the consecutive
auto-increment lock mode (the previous default) to
ensure that auto-increment values are assigned in a
predictable and repeatable order for a given sequence of
SQL statements, whereas row-based replication is not
sensitive to the execution order of SQL statements. For
more information, see
InnoDB AUTO_INCREMENT Lock Modes.
For systems that use statement-based replication, the
new
innodb_autoinc_lock_mode
default setting may break applications that depend on
sequential auto-increment values. To restore the
previous default, set
innodb_autoinc_lock_mode
to 1.
Renaming a general tablespace is supported by
ALTER
TABLESPACE ... RENAME TO syntax.
The new
innodb_dedicated_server
variable, which is disabled by default, can be used to
have InnoDB automatically configure
the following options according to the amount of memory
detected on the server:
This option is intended for MySQL server instances that run on a dedicated server. For more information, see Section 15.8.12, “Enabling Automatic Configuration for a Dedicated MySQL Server”.
The new
INFORMATION_SCHEMA.INNODB_TABLESPACES_BRIEF
view provides space, name, path, flag, and space type
data for InnoDB tablespaces.
The zlib library version bundled with MySQL was raised from version 1.2.3 to version 1.2.11. MySQL implements compression with the help of the zlib library.
If you use InnoDB compressed tables,
see Section 2.11.1.3, “Changes in MySQL 8.0” for
related upgrade implications.
Serialized Dictionary Information (SDI) is present in
all InnoDB tablespace files except
for global temporary tablespace and undo tablespace
files. SDI is serialized metadata for table and
tablespace objects. The presence of SDI data provides
metadata redundancy. For example, dictionary object
metadata may be extracted from tablespace files if the
data dictionary becomes unavailable. SDI extraction is
performed using the ibd2sdi tool. SDI
data is stored in JSON format.
The inclusion of SDI data in tablespace files increases tablespace file size. An SDI record requires a single index page, which is 16KB in size by default. However, SDI data is compressed when it is stored to reduce the storage footprint.
The InnoDB storage engine now
supports atomic DDL, which ensures that DDL operations
are either fully committed or rolled back, even if the
server halts during the operation. For more information,
see Section 13.1.1, “Atomic Data Definition Statement Support”.
Tablespace files can be moved or restored to a new
location while the server is offline using the
innodb_directories
option. For more information, see
Section 15.6.3.8, “Moving Tablespace Files While the Server is Offline”.
The following redo logging optimizations were implemented:
User threads can now write concurrently to the log buffer without synchronizing writes.
User threads can now add dirty pages to the flush list in a relaxed order.
A dedicated log thread is now responsible for writing the log buffer to the system buffers, flushing system buffers to disk, notifying user threads about written and flushed redo, maintaining the lag required for the relaxed flush list order, and write checkpoints.
System variables were added for configuring the use of spin delay by user threads waiting for flushed redo:
innodb_log_wait_for_flush_spin_hwm:
Defines the maximum average log flush time
beyond which user threads no longer spin while
waiting for flushed redo.
innodb_log_spin_cpu_abs_lwm:
Defines the minimum amount of CPU usage below
which user threads no longer spin while waiting
for flushed redo.
innodb_log_spin_cpu_pct_hwm:
Defines the maximum amount of CPU usage above
which user threads no longer spin while waiting
for flushed redo.
The
innodb_log_buffer_size
variable is now dynamic, which permits resizing of
the log buffer while the server is running.
For more information, see Section 8.5.4, “Optimizing InnoDB Redo Logging”.
As of MySQL 8.0.12, undo logging is supported for small updates to large object (LOB) data, which improves performance of LOB updates that are 100 bytes in size or less. Previously, LOB updates were a minimum of one LOB page in size, which is less than optimal for updates that might only modify a few bytes. This enhancement builds upon support added in MySQL 8.0.4 for partial update of LOB data.
As of MySQL 8.0.12, ALGORITHM=INSTANT
is supported for the following
ALTER TABLE operations:
Adding a column. This feature is also referred to as
“Instant ADD
COLUMN”. Limitations apply. See
Section 15.12.1, “Online DDL Operations”.
Adding or dropping a virtual column.
Adding or dropping a column default value.
Changing the index type.
Renaming a table.
Operations that support
ALGORITHM=INSTANT only modify
metadata in the data dictionary. No metadata locks are
taken on the table, and table data is unaffected, making
the operations instantaneous. If not specified
explicitly, ALGORITHM=INSTANT is used
by default by operations that support it. If
ALGORITHM=INSTANT is specified but
not supported, the operation fails immediately with an
error.
For more information about operations that support
ALGORITHM=INSTANT, see
Section 15.12.1, “Online DDL Operations”.
As of MySQL 8.0.13, the TempTable
storage engine supports storage of binary large object
(BLOB) type columns. This enhancement improves
performance for queries that use temporary tables
containing BLOB data. Previously, temporary tables that
contained BLOB data were stored in the on-disk storage
engine defined by
internal_tmp_disk_storage_engine.
For more information, see
Section 8.4.4, “Internal Temporary Table Use in MySQL”.
As of MySQL 8.0.13, the InnoDB
tablespace encryption feature supports general
tablespaces. Previously, only file-per-table tablespaces
could be encrypted. To support encryption of general
tablespaces, CREATE
TABLESPACE and ALTER
TABLESPACE syntax was extended to include an
ENCRYPTION clause.
The
INFORMATION_SCHEMA.INNODB_TABLESPACES
table now includes an ENCRYPTION
column that indicates whether or not a tablespace is
encrypted.
The stage/innodb/alter tablespace
(encryption) Performance Schema stage
instrument was added to permit monitoring of general
tablespace encryption operations.
To reduce the size of core files, the
innodb_buffer_pool_in_core_file
variable can be disabled to prevent
InnoDB buffer pool pages from being
written to core files.
As of MySQL 8.0.13, user-created temporary tables and
internal temporary tables created by the optimizer are
stored in session temporary tablespaces that are
allocated to a session from a pool of temporary
tablespaces. When a session disconnects, its temporary
tablespaces are truncated and released back to the pool.
In previous releases, temporary tables were created in
the global temporary tablespace
(ibtmp1), which did not return disk
space to the operating system after temporary tables
were dropped.
The
innodb_temp_tablespaces_dir
variable defines the location where session temporary
tablespaces are created. The default location is the
#innodb_temp directory in the data
directory.
The
INNODB_SESSION_TEMP_TABLESPACES
table provides metadata about session temporary
tablespaces.
The global temporary tablespace
(ibtmp1) now stores rollback
segments for changes made to user-created temporary
tables.
As of 8.0.14, when the
innodb_dedicated_server
variable is enabled, the size and number of log files
are configured according to the automatically configured
buffer pool size. Previously, log file size was
configured according to the amount of memory detected on
the server, and the number of log files was not
configured automatically.
As of 8.0.14, the ADD DATAFILE clause
of the CREATE TABLESPACE
statement is optional, which permits users without the
FILE privilege to create
tablespaces. A CREATE
TABLESPACE statement executed without an
ADD DATAFILE clause implicitly
creates a tablespace data file with a unique file name.
By default, when the amount of memory occupied by the
TempTable storage engine exceeds the memory limit
defined by the
temptable_max_ram
variable, the TempTable storage engine begins allocating
memory-mapped temporary files from disk. As of MySQL
8.0.15, this behavior is controlled by the
temptable_use_mmap
variable. Disabling
temptable_use_mmap
causes the TempTable storage engine to use
InnoDB on-disk internal temporary
tables instead of memory-mapped files as its overflow
mechanism. For more information, see
Internal Temporary Table Storage Engine.
As of MySQL 8.0.15, the InnoDB
tablespace encryption feature, which provides at-rest
data encryption, supports encryption of the
mysql system tablespace. The
mysql system tablespace contains the
mysql system database and the MySQL
data dictionary tables. For more information, see
Section 15.6.3.9, “Tablespace Encryption”.
Character set support.
The default character set has changed from
latin1 to utf8mb4.
The utf8mb4 character set has several
new collations, including
utf8mb4_ja_0900_as_cs, the first
Japanese language-specific collation available for Unicode
in MySQL. For more information, see
Section 10.10.1, “Unicode Character Sets”.
JSON enhancements. The following enhancements or additions were made to MySQL's JSON functionality:
Added the
->>
(inline path) operator, which is equivalent to calling
JSON_UNQUOTE() on the
result of JSON_EXTRACT().
This is a refinement of the column path operator
->
introduced in MySQL 5.7;
col->>"$.path" is equivalent to
JSON_UNQUOTE(col->"$.path"). The
inline path operator can be used wherever you can use
JSON_UNQUOTE(JSON_EXTRACT()), such
SELECT column lists,
WHERE and HAVING
clauses, and ORDER BY and
GROUP BY clauses. For more
information, see the description of the operator, as
well as JSON Path Syntax.
Added two JSON aggregation functions
JSON_ARRAYAGG() and
JSON_OBJECTAGG().
JSON_ARRAYAGG() takes a column or
expression as its argument, and aggregates the result as
a single JSON array. The
expression can evaluate to any MySQL data type; this
does not have to be a JSON value.
JSON_OBJECTAGG() takes two columns or
expressions which it interprets as a key and a value; it
returns the result as a single JSON
object. For more information and examples, see
Section 12.20, “Aggregate (GROUP BY) Functions”.
Added the JSON utility function
JSON_PRETTY(), which
outputs an existing JSON
value in an easy-to-read format; each JSON object member
or array value is printed on a separate line, and a
child object or array is intended 2 spaces with respect
to its parent.
This function also works with a string that can be parsed as a JSON value.
For more detailed information and examples, see Section 12.17.7, “JSON Utility Functions”.
When sorting JSON values
in a query using ORDER BY, each value
is now represented by a variable-length part of the sort
key, rather than a part of a fixed 1K in size. In many
cases this can reduce excessive usage; for example, a
scalar INT or even
BIGINT value actually requires very
few bytes, so that the remainder of this space (up to
90% or more) was taken up by padding. This change has
the following benefits for performance:
Sort buffer space is now used more effectively, so that filesorts need not flush to disk as early or often as with fixed-length sort keys. This means that more data can be sorted in memory, avoiding unnecessary disk access.
Shorter keys can be compared more quickly than longer ones, providing a noticeable improvement in performance. This is true for sorts performed entirely in memory as well as for sorts that require writing to and reading from disk.
Added support in MySQL 8.0.2 for partial, in-place
updates of JSON column values, which
is more efficient than completely removing an existing
JSON value and writing a new one in its place, as was
done previously when updating any
JSON column. For this optimization to
be applied, the update must be applied using
JSON_SET(),
JSON_REPLACE(), or
JSON_REMOVE(). New
elements cannot be added to the JSON document being
updated; values within the document cannot take more
space than they did before the update. See
Partial Updates of JSON Values, for a detailed
discussion of the requirements.
Partial updates of JSON documents can be written to the
binary log, taking up less space than logging complete
JSON documents. Partial updates are always logged as
such when statement-based replication is in use. For
this to work with row-based replication, you must first
set
binlog_row_value_options=PARTIAL_JSON;
see this variable's description for more
information.
Added the JSON utility functions
JSON_STORAGE_SIZE() and
JSON_STORAGE_FREE().
JSON_STORAGE_SIZE() returns the
storage space in bytes used for the binary
representation of a JSON document prior to any partial
update (see previous item).
JSON_STORAGE_FREE() shows the amount
of space remaining in a table column of type
JSON after it has been
partially updated using JSON_SET() or
JSON_REPLACE(); this is greater than
zero if the binary representation of the new value is
less than that of the previous value.
Each of these functions also accepts a valid string
representation of a JSON document. For such a value,
JSON_STORAGE_SIZE() returns the space
used by its binary representation following its
conversion to a JSON document. For a variable containing
the string representation of a JSON document,
JSON_STORAGE_FREE() returns zero.
Either function produces an error if its (non-null)
argument cannot be parsed as a valid JSON document, and
NULL if the argument is
NULL.
For more information and examples, see Section 12.17.7, “JSON Utility Functions”.
JSON_STORAGE_SIZE() and
JSON_STORAGE_FREE() were implemented
in MySQL 8.0.2.
Added support in MySQL 8.0.2 for ranges such as
$[1 to 5] in XPath expressions. Also
added support in this version for the
last keyword and relative addressing,
such that $[last] always selects the
last (highest-numbered) element in the array and
$[last-1] the next to last element.
last and expressions using it can
also be included in range definitions; for example,
$[last-2 to last-1] returns the last
two elements but one from an array. See
Searching and Modifying JSON Values, for additional information
and examples.
Added a JSON merge function intended to conform to
RFC
7396.
JSON_MERGE_PATCH(), when
used on 2 JSON objects, merges them into a single JSON
object that has as members a union of the following
sets:
Each member of the first object for which there is no member with the same key in the second object.
Each member of the second object for which there is
no member having the same key in the first object,
and whose value is not the JSON
null literal.
Each member having a key that exists in both
objects, and whose value in the second object is not
the JSON null literal.
As part of this work, the
JSON_MERGE() function has
been renamed
JSON_MERGE_PRESERVE().
JSON_MERGE() continues to be
recognized as an alias for
JSON_MERGE_PRESERVE() in MySQL
8.0, but is now deprecated and is subject
to removal in a future version of MySQL.
For more information and examples, see Section 12.17.4, “Functions That Modify JSON Values”.
Implemented “last duplicate key wins”
normalization of duplicate keys, consistent with
RFC
7159 and most JavaScript parsers. An example of
this behavior is shown here, where only the rightmost
member having the key x is preserved:
mysql> SELECTJSON_OBJECT('x', '32', 'y', '[true, false]',>'x', '"abc"', 'x', '100') AS Result;+------------------------------------+ | Result | +------------------------------------+ | {"x": "100", "y": "[true, false]"} | +------------------------------------+ 1 row in set (0.00 sec)
Values inserted into MySQL
JSON columns are also
normalized in this way, as shown in this example:
mysql>CREATE TABLE t1 (c1 JSON);mysql>INSERT INTO t1 VALUES ('{"x": 17, "x": "red", "x": [3, 5, 7]}');mysql>SELECT c1 FROM t1;+------------------+ | c1 | +------------------+ | {"x": [3, 5, 7]} | +------------------+
This is an incompatible change from previous versions of MySQL, where a “first duplicate key wins” algorithm was used in such cases.
See Normalization, Merging, and Autowrapping of JSON Values, for more information and examples.
Added the JSON_TABLE()
function in MySQL 8.0.4. This function accepts JSON data
and returns it as a relational table having the
specified columns.
This function has the syntax
JSON_TABLE(, where
expr,
path COLUMNS
column_list) [AS]
alias)expr is an expression that
returns JSON data, path is a
JSON path applied to the source, and
column_list is a list of
column definitions. An example is shown here:
mysql>SELECT *->FROM->JSON_TABLE(->'[{"a":3,"b":"0"},{"a":"3","b":"1"},{"a":2,"b":1},{"a":0},{"b":[1,2]}]',->"$[*]" COLUMNS(->rowid FOR ORDINALITY,-> ->xa INT EXISTS PATH "$.a",->xb INT EXISTS PATH "$.b",-> ->sa VARCHAR(100) PATH "$.a",->sb VARCHAR(100) PATH "$.b",-> ->ja JSON PATH "$.a",->jb JSON PATH "$.b"->)->) AS jt1;+-------+------+------+------+------+------+--------+ | rowid | xa | xb | sa | sb | ja | jb | +-------+------+------+------+------+------+--------+ | 1 | 1 | 1 | 3 | 0 | 3 | "0" | | 2 | 1 | 1 | 3 | 1 | "3" | "1" | | 3 | 1 | 1 | 2 | 1 | 2 | 1 | | 4 | 1 | 0 | 0 | NULL | 0 | NULL | | 5 | 0 | 1 | NULL | NULL | NULL | [1, 2] | +-------+------+------+------+------+------+--------+
The JSON source expression can be any expression that
yields a valid JSON document, including a JSON literal,
a table column, or a function call that returns JSON
such as JSON_EXTRACT(t1, data,
'$.post.comments'). For more information, see
Section 12.17.6, “JSON Table Functions”.
Data type support.
MySQL now supports use of expressions as default values in
data type specifications. This includes the use of
expressions as default values for the
BLOB,
TEXT,
GEOMETRY, and
JSON data types, which
previously could not be assigned default values at all.
For details, see Section 11.7, “Data Type Default Values”.
Optimizer. These optimizer enhancements were added:
MySQL now supports invisible indexes. An invisible index is not used by the optimizer at all, but is otherwise maintained normally. Indexes are visible by default. Invisible indexes make it possible to test the effect of removing an index on query performance, without making a destructive change that must be undone should the index turn out to be required. See Section 8.3.12, “Invisible Indexes”.
MySQL now supports descending indexes:
DESC in an index definition is no
longer ignored but causes storage of key values in
descending order. Previously, indexes could be scanned
in reverse order but at a performance penalty. A
descending index can be scanned in forward order, which
is more efficient. Descending indexes also make it
possible for the optimizer to use multiple-column
indexes when the most efficient scan order mixes
ascending order for some columns and descending order
for others. See Section 8.3.13, “Descending Indexes”.
MySQL now supports creation of functional index key
parts that index expression values rather than column
values. Functional key parts enable indexing of values
that cannot be indexed otherwise, such as
JSON values. For details,
see Section 13.1.15, “CREATE INDEX Syntax”.
In MySQL 8.0.14 and later, trivial
WHERE conditions arising from
constant literal expressions are removed during
preparation, rather than later on during optimization.
Removal of the condition earlier in the process makes it
possible to simplify joins for queries with outer joins
having trivial conditions, such as this one:
SELECT * FROM t1 LEFT JOIN t2 ONcondition_1WHEREcondition_2OR 0 = 1
The optimizer now sees during preparation that 0 = 1 is
always false, making OR 0 = 1
redundant, and removes it, leaving this:
SELECT * FROM t1 LEFT JOIN t2 ONcondition_1wherecondition_2
Now the optimizer can rewrite the query as an inner join, like this:
SELECT * FROM t1 LEFT JOIN t2 WHEREcondition_1ANDcondition_2
For more information, see Section 8.2.1.8, “Outer Join Optimization”.
Common table expressions.
MySQL now supports common table expressions, both
nonrecursive and recursive. Common table expressions
enable use of named temporary result sets, implemented by
permitting a WITH clause
preceding SELECT statements
and certain other statements. For more information, see
Section 13.2.13, “WITH Syntax (Common Table Expressions)”.
Window functions.
MySQL now supports window functions that, for each row
from a query, perform a calculation using rows related to
that row. These include functions such as
RANK(),
LAG(), and
NTILE(). In addition,
several existing aggregate functions now can be used as
window functions; for example,
SUM() and
AVG(). For more
information, see Section 12.21, “Window Functions”.
Lateral derived tables.
A derived table now may be preceded by the
LATERAL keyword to specify that it is
permitted to refer to (depend on) columns of preceding
tables in the same FROM clause. Lateral
derived tables make possible certain SQL operations that
cannot be done with nonlateral derived tables or that
require less-efficient workarounds. See
Section 13.2.11.9, “Lateral Derived Tables”.
Regular expression support.
Previously, MySQL used the Henry Spencer regular
expression library to support regular expression operators
(REGEXP,
RLIKE).
Regular expression support has been reimplemented using
International Components for Unicode (ICU), which provides
full Unicode support and is multibyte safe. The
REGEXP_LIKE() function
performs regular expression matching in the manner of the
REGEXP and
RLIKE
operators, which now are synonyms for that function. In
addition, the
REGEXP_INSTR(),
REGEXP_REPLACE(), and
REGEXP_SUBSTR() functions
are available to find match positions and perform
substring substitution and extraction, respectively. The
regexp_stack_limit and
regexp_time_limit system
variables provide control over resource consumption by the
match engine. For more information, see
Section 12.5.2, “Regular Expressions”. For information about ways in
which applications that use regular expressions may be
affected by the implementation change, see
Regular Expression Compatibility Considerations.
Internal temporary tables.
The TempTable storage engine replaces
the MEMORY storage engine as the
default engine for in-memory internal temporary tables.
The TempTable storage engine provides
efficient storage for
VARCHAR and
VARBINARY columns. The
internal_tmp_mem_storage_engine
session variable defines the storage engine for in-memory
internal temporary tables. Permitted values are
TempTable (the default) and
MEMORY. The
temptable_max_ram
variable defines the maximum amount of memory that the
TempTable storage engine can use before
data is stored to disk.
Logging.
Error logging was rewritten to use the MySQL component
architecture. Traditional error logging is implemented
using built-in components, and logging using the system
log is implemented as a loadable component. In addition, a
loadable JSON log writer is available. To control which
log components to enable, use the
log_error_services system
variable. For more information, see
Section 5.4.2, “The Error Log”.
Backup lock.
A new type of backup lock permits DML during an online
backup while preventing operations that could result in an
inconsistent snapshot. The new backup lock is supported by
LOCK INSTANCE FOR BACKUP
and
UNLOCK
INSTANCE syntax. The
BACKUP_ADMIN privilege is
required to use these statements.
Replication. The following enhancements have been made to MySQL Replication:
MySQL Replication now supports binary logging of partial
updates to JSON documents using a compact binary format,
saving space in the log over logging complete JSON
documents. Such compact logging is done automatically
when statement-based logging is in use, and can be
enabled by setting the new
binlog_row_value_options system
variable to PARTIAL_JSON. For more
information, see Partial Updates of JSON Values,
as well as the description of
binlog_row_value_options.
Connection management.
MySQL Server now permits a TCP/IP port to be configured
specifically for administrative connections. This provides
an alternative to the single administrative connection
that is permitted on the network interfaces used for
ordinary connections even when
max_connections
connections are already established. See
Section 8.12.4.1, “How MySQL Handles Client Connections”.
Plugins. Previously, MySQL plugins could be written in C or C++. MySQL header files used by plugins now contain C++ code, which means that plugins must be written in C++, not C.
The following features are deprecated in MySQL 8.0 and may be or will be removed in a future series. Where alternatives are shown, applications should be updated to use them.
For applications that use features deprecated in MySQL 8.0 that have been removed in a higher MySQL series, statements may fail when replicated from a MySQL 8.0 master to a higher-series slave, or may have different effects on master and slave. To avoid such problems, applications that use features deprecated in 8.0 should be revised to avoid them and use alternatives when possible.
The utf8mb3 character set is deprecated.
Please use utf8mb4 instead.
Because caching_sha2_password is the
default authentication plugin in MySQL 8.0 and provides a
superset of the capabilities of the
sha256_password authentication plugin,
sha256_password is deprecated and will be
removed in a future MySQL version. MySQL accounts that
authenticate using sha256_password should
be migrated to use caching_sha2_password
instead.
The validate_password plugin has been
reimplemented to use the server component infrastructure.
The plugin form of validate_password is
still available but is deprecated and will be removed in a
future version of MySQL. MySQL installations that use the
plugin should make the transition to using the component
instead. See
Section 6.5.3.3, “Transitioning to the Password Validation Component”.
The ALTER TABLESPACE and
DROP TABLESPACE
ENGINE clause is deprecated.
The
PAD_CHAR_TO_FULL_LENGTH
SQL mode is deprecated.
The JSON_MERGE() function is
deprecated. Use
JSON_MERGE_PRESERVE()
instead.
Support for TABLESPACE =
innodb_file_per_table and TABLESPACE =
innodb_temporary clauses with
CREATE
TEMPORARY TABLE is deprecated as of MySQL 8.0.13.
The following items are obsolete and have been removed in MySQL 8.0. Where alternatives are shown, applications should be updated to use them.
For MySQL 5.7 applications that use features removed in MySQL 8.0, statements may fail when replicated from a MySQL 5.7 master to a MySQL 8.0 slave, or may have different effects on master and slave. To avoid such problems, applications that use features removed in MySQL 8.0 should be revised to avoid them and use alternatives when possible.
The innodb_locks_unsafe_for_binlog system
variable was removed. The READ
COMMITTED isolation level provides similar
functionality.
The information_schema_stats variable,
introduced in MySQL 8.0.0, was removed and replaced by
information_schema_stats_expiry
in MySQL 8.0.3.
information_schema_stats_expiry defines
an expiration setting for cached
INFORMATION_SCHEMA table
statistics. For more information, see
Section 8.2.3, “Optimizing INFORMATION_SCHEMA Queries”.
Code related to obsoleted InnoDB system
tables was removed in MySQL 8.0.3.
INFORMATION_SCHEMA views based
on InnoDB system tables were replaced by
internal system views on data dictionary tables. Affected
InnoDB
INFORMATION_SCHEMA views were
renamed:
Table 1.1 Renamed InnoDB Information Schema Views
| Old Name | New Name |
|---|---|
INNODB_SYS_COLUMNS |
INNODB_COLUMNS |
INNODB_SYS_DATAFILES |
INNODB_DATAFILES |
INNODB_SYS_FIELDS |
INNODB_FIELDS |
INNODB_SYS_FOREIGN |
INNODB_FOREIGN |
INNODB_SYS_FOREIGN_COLS |
INNODB_FOREIGN_COLS |
INNODB_SYS_INDEXES |
INNODB_INDEXES |
INNODB_SYS_TABLES |
INNODB_TABLES |
INNODB_SYS_TABLESPACES |
INNODB_TABLESPACES |
INNODB_SYS_TABLESTATS |
INNODB_TABLESTATS |
INNODB_SYS_VIRTUAL |
INNODB_VIRTUAL |
After upgrading to MySQL 8.0.3 or later, update any scripts
that reference previous InnoDB
INFORMATION_SCHEMA view names.
The following features related to account management are removed:
Using GRANT to create
users. Instead, use CREATE
USER. Following this practice makes the
NO_AUTO_CREATE_USER SQL mode
immaterial for GRANT
statements, so it too is removed.
Using GRANT to modify
account properties other than privilege assignments.
This includes authentication, SSL, and resource-limit
properties. Instead, establish such properties at
account-creation time with CREATE
USER or modify them afterward with
ALTER USER.
IDENTIFIED BY PASSWORD
'
syntax for hash_string'CREATE USER
and GRANT. Instead, use
IDENTIFIED WITH
for
auth_plugin AS
'hash_string'CREATE USER and
ALTER USER, where the
'
value is in a format compatible with the named plugin.
hash_string'
Additionally, because IDENTIFIED BY
PASSWORD syntax was removed, the
log_builtin_as_identified_by_password
system variable is superfluous and was removed.
The PASSWORD() function.
Additionally, PASSWORD() removal
means that
SET
PASSWORD ... =
PASSWORD('
syntax is no longer available.
auth_string')
The old_passwords
system variable.
The query cache was removed. Removal includes these items:
The FLUSH QUERY CACHE and
RESET QUERY CACHE statements.
These system variables:
query_cache_limit,
query_cache_min_res_unit,
query_cache_size,
query_cache_type,
query_cache_wlock_invalidate.
These status variables:
Qcache_free_blocks,
Qcache_free_memory,
Qcache_hits,
Qcache_inserts,
Qcache_lowmem_prunes,
Qcache_not_cached,
Qcache_queries_in_cache,
Qcache_total_blocks.
These thread states: checking privileges on
cached query, checking query cache
for query, invalidating query cache
entries, sending cached result to
client, storing result in query
cache, Waiting for query cache
lock.
The SQL_CACHE
SELECT modifier.
These deprecated query cache items remain deprecated, but have no effect, and will be removed in a future MySQL release:
SQL_NO_CACHE
SELECT modifier.
The ndb_cache_check_time system
variable.
The have_query_cache system variable
remains deprecated, always has a value of
NO, and will be removed in a future MySQL
release.
The data dictionary provides information about database
objects, so the server no longer checks directory names in
the data directory to find databases. Consequently, the
--ignore-db-dir option and
ignore_db_dirs system variables are
extraneous and are removed.
The tx_isolation and
tx_read_only system variables have been
removed. Use
transaction_isolation and
transaction_read_only
instead.
The sync_frm system variable has been
removed because .frm files have become
obsolete.
The secure_auth system variable and
--secure-auth client option have been
removed. The MYSQL_SECURE_AUTH option for
the mysql_options() C API
function was removed.
The multi_range_count system variable is
removed.
The log_warnings system variable and
--log-warnings server option have been
removed. Use the
log_error_verbosity system
variable instead.
The global scope for the
sql_log_bin system variable
was removed. sql_log_bin has session
scope only, and applications that rely on accessing
@@GLOBAL.sql_log_bin should be adjusted.
The metadata_locks_cache_size and
metadata_locks_hash_instances system
variables are removed.
The unused date_format,
datetime_format,
time_format, and
max_tmp_tables system variables are
removed.
These deprecated compatibility SQL modes are removed:
DB2, MAXDB,
MSSQL, MYSQL323,
MYSQL40, ORACLE,
POSTGRESQL,
NO_FIELD_OPTIONS,
NO_KEY_OPTIONS,
NO_TABLE_OPTIONS. They can no longer be
assigned to the sql_mode system variable
or used as permitted values for the
mysqldump
--compatible option.
Removal of MAXDB means that the
TIMESTAMP data type for
CREATE TABLE or
ALTER TABLE is treated as
TIMESTAMP, and is no longer
treated as DATETIME.
The deprecated ASC or
DESC qualifiers for GROUP
BY clauses are removed. Queries that previously
relied on GROUP BY sorting may produce
results that differ from previous MySQL versions. To produce
a given sort order, provide an ORDER BY
clause.
The EXTENDED and
PARTITIONS keywords for the
EXPLAIN statement have been
removed. These keywords are unnecessary because their effect
is always enabled.
These encryption-related items are removed:
The ENCRYPT() function.
The DES_ENCRYPT(), and
DES_DECRYPT() functions,
the --des-key-file
option, the have_crypt
system variable, the DES_KEY_FILE
option for the FLUSH
statement, and the HAVE_CRYPT
CMake option.
In place of the removed encryption functions: For
ENCRYPT(), consider using
SHA2() instead for one-way
hashing. For the others, consider using
AES_ENCRYPT() and
AES_DECRYPT() instead.
In MySQL 5.7, several spatial functions
available under multiple names were deprecated to move in
the direction of making the spatial function namespace more
consistent, the goal being that each spatial function name
begin with ST_ if it performs an exact
operation, or with MBR if it performs an
operation based on minimum bounding rectangles. In MySQL
8.0, the deprecated functions are removed to
leave only the corresponding ST_ and
MBR functions:
These functions are removed in favor of the
MBR names:
Contains(),
Disjoint(),
Equals(),
Intersects(),
Overlaps(),
Within().
These functions are removed in favor of the
ST_ names: Area(),
AsBinary(),
AsText(), AsWKB(),
AsWKT(), Buffer(),
Centroid(),
ConvexHull(),
Crosses(),
Dimension(),
Distance(),
EndPoint(),
Envelope(),
ExteriorRing(),
GeomCollFromText(),
GeomCollFromWKB(),
GeomFromText(),
GeomFromWKB(),
GeometryCollectionFromText(),
GeometryCollectionFromWKB(),
GeometryFromText(),
GeometryFromWKB(),
GeometryN(),
GeometryType(),
InteriorRingN(),
IsClosed(),
IsEmpty(),
IsSimple(),
LineFromText(),
LineFromWKB(),
LineStringFromText(),
LineStringFromWKB(),
MLineFromText(),
MLineFromWKB(),
MPointFromText(),
MPointFromWKB(),
MPolyFromText(),
MPolyFromWKB(),
MultiLineStringFromText(),
MultiLineStringFromWKB(),
MultiPointFromText(),
MultiPointFromWKB(),
MultiPolygonFromText(),
MultiPolygonFromWKB(),
NumGeometries(),
NumInteriorRings(),
NumPoints(),
PointFromText(),
PointFromWKB(),
PointN(),
PolyFromText(),
PolyFromWKB(),
PolygonFromText(),
PolygonFromWKB(),
SRID(),
StartPoint(),
Touches(), X(),
Y().
GLength() is removed in favor of
ST_Length().
The functions described in Section 12.16.4, “Functions That Create Geometry Values from WKB Values” previously accepted either WKB strings or geometry arguments. Geometry arguments are no longer permitted and produce an error. See that section for guidelines for migrating queries away from using geometry arguments.
The parser no longer treats \N as a
synonym for NULL in SQL statements. Use
NULL instead.
This change does not affect text file import or export
operations performed with LOAD
DATA or
SELECT ... INTO
OUTFILE, for which NULL
continues to be represented by \N. See
Section 13.2.7, “LOAD DATA Syntax”.
PROCEDURE ANALYSE() syntax is removed.
The client-side --ssl and
--ssl-verify-server-cert options have been
removed. Use
--ssl-mode=REQUIRED instead
of --ssl=1 or
--enable-ssl. Use
--ssl-mode=DISABLED instead
of --ssl=0, --skip-ssl, or
--disable-ssl. Use
--ssl-mode=VERIFY_IDENTITY
instead of --ssl-verify-server-cert
options. (The server-side
--ssl option remains
unchanged.)
For the C API, MYSQL_OPT_SSL_ENFORCE and
MYSQL_OPT_SSL_VERIFY_SERVER_CERT options
for mysql_options()
correspond to the client-side --ssl and
--ssl-verify-server-cert options and are
removed. Use MYSQL_OPT_SSL_MODE with an
option value of SSL_MODE_REQUIRED or
SSL_MODE_VERIFY_IDENTITY instead.
The --temp-pool server option
was removed.
The --ignore-builtin-innodb
server option and
ignore_builtin_innodb
system variable are removed.
The server no longer performs conversion of pre-MySQL 5.1
database names containing special characters to 5.1 format
with the addition of a #mysql50# prefix.
Because these conversions are no longer performed, the
--fix-db-names and
--fix-table-names options for
mysqlcheck, the UPGRADE DATA
DIRECTORY NAME clause for the
ALTER DATABASE statement, and
the Com_alter_db_upgrade status variable
are removed.
Upgrades are supported only from one major version to another (for example, 5.0 to 5.1, or 5.1 to 5.5), so there should be little remaining need for conversion of older 5.0 database names to current versions of MySQL. As a workaround, upgrade a MySQL 5.0 installation to MySQL 5.1 before upgrading to a more recent release.
The mysql_install_db program has been
removed from MySQL distributions. Data directory
initialization should be performed by invoking
mysqld with the
--initialize or
--initialize-insecure option
instead. In addition, the --bootstrap
option for mysqld that was used by
mysql_install_db was removed, and the
INSTALL_SCRIPTDIR CMake
option that controlled the installation location for
mysql_install_db was removed.
The generic partitioning handler was removed from the MySQL
server. In order to support partitioning of a given table,
the storage engine used for the table must now provide its
own (“native”) partitioning handler. The
--partition and
--skip-partition options are removed from
the MySQL Server, and partitioning-related entries are no
longer shown in the output of SHOW
PLUGINS or in the
INFORMATION_SCHEMA.PLUGINS
table.
Two MySQL storage engines currently provide native
partitioning
support—InnoDB and
NDB; of these, only
InnoDB is supported in MySQL
8.0. Any attempt to create partitioned tables
in MySQL 8.0 using any other storage engine
fails.
Ramifications for upgrades.
The direct upgrade of a partitioned table using a storage
engine other than InnoDB (such as
MyISAM) from MySQL
5.7 (or earlier) to MySQL 8.0
is not supported. There are two options for handling such
a table:
Remove the table's partitioning, using
ALTER
TABLE ... REMOVE PARTITIONING.
Change the storage engine used for the table to
InnoDB, with
ALTER TABLE
... ENGINE=INNODB.
At least one of the two operations just listed must be
performed for each partitioned non-InnoDB
table prior to upgrading the server to MySQL
8.0. Otherwise, such a table cannot be used
following the upgrade.
Due to the fact that table creation statements that would
result in a partitioned table using a storage engine without
partitioning support now fail with an error
(ER_CHECK_NOT_IMPLEMENTED), you must
make sure that any statements in a dump file (such as that
written by mysqldump) from an older
version of MySQL that you wish to import into a MySQL
8.0 server that create partitioned tables do
not also specify a storage engine such as
MyISAM that has no native partitioning
handler. You can do this by performing either of the
following:
Remove any references to partitioning from
CREATE TABLE statements that use a
value for the STORAGE ENGINE option
other than InnoDB.
Specifying the storage engine as
InnoDB, or allow
InnoDB to be used as the table's
storage engine by default.
For more information, see Section 23.6.2, “Partitioning Limitations Relating to Storage Engines”.
System and status variable information is no longer
maintained in the INFORMATION_SCHEMA.
These tables are removed:
GLOBAL_VARIABLES,
SESSION_VARIABLES,
GLOBAL_STATUS,
SESSION_STATUS. Use the corresponding
Performance Schema tables instead. See
Section 26.12.13, “Performance Schema System Variable Tables”,
and
Section 26.12.14, “Performance Schema Status Variable Tables”.
In addition, the show_compatibility_56
system variable was removed. It was used in the transition
period during which system and status variable information
in INFORMATION_SCHEMA tables was moved to
Performance Schema tables, and is no longer needed. These
status variables are removed:
Slave_heartbeat_period,
Slave_last_heartbeat,
Slave_received_heartbeats,
Slave_retried_transactions,
Slave_running. The information they
provided is available in Performance Schema tables; see
Migrating to Performance Schema System and Status Variable Tables.
The Performance Schema setup_timers table
was removed, as was the TICK row in the
performance_timers table.
The libmysqld embedded server library is
removed, along with:
The mysql_options()
MYSQL_OPT_GUESS_CONNECTION,
MYSQL_OPT_USE_EMBEDDED_CONNECTION,
MYSQL_OPT_USE_REMOTE_CONNECTION, and
MYSQL_SET_CLIENT_IP options
The mysql_config
--libmysqld-libs,
--embedded-libs, and
--embedded options
The CMake
WITH_EMBEDDED_SERVER,
WITH_EMBEDDED_SHARED_LIBRARY, and
INSTALL_SECURE_FILE_PRIV_EMBEDDEDDIR
options
The (undocumented) mysql
--server-arg option
The mysqltest
--embedded-server,
--server-arg, and
--server-file options
The mysqltest_embedded and mysql_client_test_embedded test programs
The mysql_plugin utility was removed.
Alternatives include loading plugins at server startup using
the --plugin-load or
--plugin-load-add option, or
at runtime using the INSTALL
PLUGIN statement.
The resolveip utility is removed. nslookup, host, or dig can be used instead.
The resolve_stack_dump utility is removed. Stack traces from official MySQL builds are always symbolized, so there is no need to use resolve_stack_dump.
The following server error codes are not used and have been removed. Applications that test specifically for any of these errors should be updated.
ER_BINLOG_READ_EVENT_CHECKSUM_FAILURE ER_BINLOG_ROW_RBR_TO_SBR ER_BINLOG_ROW_WRONG_TABLE_DEF ER_CANT_ACTIVATE_LOG ER_CANT_CHANGE_GTID_NEXT_IN_TRANSACTION ER_CANT_CREATE_FEDERATED_TABLE ER_CANT_CREATE_SROUTINE ER_CANT_DELETE_FILE ER_CANT_GET_WD ER_CANT_SET_GTID_PURGED_WHEN_GTID_MODE_IS_OFF ER_CANT_SET_WD ER_CANT_WRITE_LOCK_LOG_TABLE ER_CREATE_DB_WITH_READ_LOCK ER_CYCLIC_REFERENCE ER_DB_DROP_DELETE ER_DELAYED_NOT_SUPPORTED ER_DIFF_GROUPS_PROC ER_DISK_FULL ER_DROP_DB_WITH_READ_LOCK ER_DROP_USER ER_DUMP_NOT_IMPLEMENTED ER_ERROR_DURING_CHECKPOINT ER_ERROR_ON_CLOSE ER_EVENTS_DB_ERROR ER_EVENT_CANNOT_DELETE ER_EVENT_CANT_ALTER ER_EVENT_COMPILE_ERROR ER_EVENT_DATA_TOO_LONG ER_EVENT_DROP_FAILED ER_EVENT_MODIFY_QUEUE_ERROR ER_EVENT_NEITHER_M_EXPR_NOR_M_AT ER_EVENT_OPEN_TABLE_FAILED ER_EVENT_STORE_FAILED ER_EXEC_STMT_WITH_OPEN_CURSOR ER_FAILED_ROUTINE_BREAK_BINLOG ER_FLUSH_MASTER_BINLOG_CLOSED ER_FORM_NOT_FOUND ER_FOUND_GTID_EVENT_WHEN_GTID_MODE_IS_OFF__UNUSED ER_FRM_UNKNOWN_TYPE ER_GOT_SIGNAL ER_GRANT_PLUGIN_USER_EXISTS ER_GTID_MODE_REQUIRES_BINLOG ER_GTID_NEXT_IS_NOT_IN_GTID_NEXT_LIST ER_HASHCHK ER_INDEX_REBUILD ER_INNODB_NO_FT_USES_PARSER ER_LIST_OF_FIELDS_ONLY_IN_HASH_ERROR ER_LOAD_DATA_INVALID_COLUMN_UNUSED ER_LOGGING_PROHIBIT_CHANGING_OF ER_MALFORMED_DEFINER ER_MASTER_KEY_ROTATION_ERROR_BY_SE ER_NDB_CANT_SWITCH_BINLOG_FORMAT ER_NEVER_USED ER_NISAMCHK ER_NO_CONST_EXPR_IN_RANGE_OR_LIST_ERROR ER_NO_FILE_MAPPING ER_NO_GROUP_FOR_PROC ER_NO_RAID_COMPILED ER_NO_SUCH_KEY_VALUE ER_NO_SUCH_PARTITION__UNUSED ER_OBSOLETE_CANNOT_LOAD_FROM_TABLE ER_OBSOLETE_COL_COUNT_DOESNT_MATCH_CORRUPTED ER_ORDER_WITH_PROC ER_PARTITION_SUBPARTITION_ERROR ER_PARTITION_SUBPART_MIX_ERROR ER_PART_STATE_ERROR ER_PASSWD_LENGTH ER_QUERY_ON_MASTER ER_RBR_NOT_AVAILABLE ER_SKIPPING_LOGGED_TRANSACTION ER_SLAVE_CHANNEL_DELETE ER_SLAVE_MULTIPLE_CHANNELS_HOST_PORT ER_SLAVE_MUST_STOP ER_SLAVE_WAS_NOT_RUNNING ER_SLAVE_WAS_RUNNING ER_SP_GOTO_IN_HNDLR ER_SP_PROC_TABLE_CORRUPT ER_SQL_MODE_NO_EFFECT ER_SR_INVALID_CREATION_CTX ER_TABLE_NEEDS_UPG_PART ER_TOO_MUCH_AUTO_TIMESTAMP_COLS ER_UNEXPECTED_EOF ER_UNION_TABLES_IN_DIFFERENT_DIR ER_UNSUPPORTED_BY_REPLICATION_THREAD ER_UNUSED1 ER_UNUSED2 ER_UNUSED3 ER_UNUSED4 ER_UNUSED5 ER_UNUSED6 ER_VIEW_SELECT_DERIVED_UNUSED ER_WRONG_MAGIC ER_WSAS_FAILED
The deprecated INFORMATION_SCHEMA
INNODB_LOCKS and
INNODB_LOCK_WAITS tables are
removed. Use the Performance Schema
data_locks and
data_lock_waits tables instead.
In MySQL 5.7, the LOCK_TABLE column in
the INNODB_LOCKS table and
the locked_table column in the
sys schema
innodb_lock_waits and
x$innodb_lock_waits views
contain combined schema/table name values. In MySQL 8.0,
the data_locks table and the
sys schema views contain separate
schema name and table name columns. See
Section 27.4.3.9, “The innodb_lock_waits and x$innodb_lock_waits Views”.
InnoDB no longer supports compressed
temporary tables. When
innodb_strict_mode is
enabled (the default),
CREATE
TEMPORARY TABLE returns an error if
ROW_FORMAT=COMPRESSED or
KEY_BLOCK_SIZE is specified. If
innodb_strict_mode is
disabled, warnings are issued and the temporary table is
created using a non-compressed row format.
InnoDB no longer creates
.isl files (InnoDB
Symbolic Link files) when creating tablespace data files
outside of the MySQL data directory. The
innodb_directories option
now supports locating tablespace files created outside of
the data directory.
With this change, moving a remote tablespace while the
server is offline by manually modifying an
.isl file is no longer supported.
Moving remote tablespace files is now supported by the
innodb_directories option.
See Section 15.6.3.8, “Moving Tablespace Files While the Server is Offline”.
The following InnoDB file format
variables were removed:
innodb_file_format
innodb_file_format_check
innodb_file_format_max
innodb_large_prefix
File format variables were necessary for creating tables
compatible with earlier versions of
InnoDB in MySQL 5.1. Now that MySQL 5.1
has reached the end of its product lifecycle, these options
are no longer required.
The FILE_FORMAT column was removed from
the INNODB_TABLES and
INNODB_TABLESPACES Information
Schema tables.
The innodb_support_xa system variable,
which enables support for two-phase commit in XA
transactions, was removed. InnoDB support
for two-phase commit in XA transactions is always enabled.
Support for DTrace was removed.
The JSON_APPEND() function was removed.
Use JSON_ARRAY_APPEND()
instead.
Support for placing table partitions in shared
InnoDB tablespaces was removed in MySQL
8.0.13. Shared tablespaces include the
InnoDB system tablespace and general
tablespaces. For information about identifying partitions in
shared tablespaces and moving them to file-per-table
tablespaces, see Section 2.11.1.4, “Preparing Your Installation for Upgrade”.
Support for setting user variables in statements other than
SET
was deprecated in MySQL 8.0.13. This functionality is
subject to removal in MySQL 9.0.
The --ndb perror option
was removed. Use the ndb_perror utility
instead.
The innodb_undo_logs variable was
removed. The
innodb_rollback_segments
variables performs the same function and should be used
instead.
The Innodb_available_undo_logs status
variable was removed. The number of available rollback
segments per tablespace may be retrieved using SHOW
VARIABLES LIKE 'innodb_rollback_segments';
As of MySQL 8.0.14, the previously deprecated
innodb_undo_tablespaces
variable is no longer configurable. For more information,
see Section 15.6.3.4, “Undo Tablespaces”.
This section lists server variables, status variables, and options that were added for the first time, have been deprecated, or have been removed in MySQL 8.0.
The following system variables, status variables, and options are new in MySQL 8.0, and have not been included in any previous release series.
Acl_cache_items_count:
Number of cached privilege objects. Added in MySQL 8.0.0.
Audit_log_current_size:
Audit log file current size. Added in MySQL 8.0.11.
Audit_log_event_max_drop_size:
Size of largest dropped audited event. Added in MySQL 8.0.11.
Audit_log_events:
Number of handled audited events. Added in MySQL 8.0.11.
Audit_log_events_filtered:
Number of filtered audited events. Added in MySQL 8.0.11.
Audit_log_events_lost:
Number of dropped audited events. Added in MySQL 8.0.11.
Audit_log_events_written:
Number of written audited events. Added in MySQL 8.0.11.
Audit_log_total_size:
Combined size of written audited events. Added in MySQL
8.0.11.
Audit_log_write_waits:
Number of write-delayed audited events. Added in MySQL 8.0.11.
Caching_sha2_password_rsa_public_key:
caching_sha2_password authentication plugin RSA public key
value. Added in MySQL 8.0.4.
Com_alter_resource_group:
Count of ALTER RESOURCE GROUP statements. Added in MySQL
8.0.3.
Com_alter_user_default_role:
Count of ALTER USER ... DEFAULT ROLE statements. Added in
MySQL 8.0.0.
Com_create_resource_group:
Count of CREATE RESOURCE GROUP statements. Added in MySQL
8.0.3.
Com_create_role:
Count of CREATE ROLE statements. Added in MySQL 8.0.0.
Com_drop_resource_group:
Count of DROP RESOURCE GROUP statements. Added in MySQL 8.0.3.
Com_drop_role:
Count of DROP ROLE statements. Added in MySQL 8.0.0.
Com_grant_roles:
Count of GRANT ROLE statements. Added in MySQL 8.0.0.
Com_install_component:
Count of INSTALL COMPONENT statements. Added in MySQL 8.0.0.
Com_revoke_roles:
Count of REVOKE ROLES statements. Added in MySQL 8.0.0.
Com_set_resource_group:
Count of SET RESOURCE GROUP statements. Added in MySQL 8.0.3.
Com_set_role:
Count of SET ROLE statements. Added in MySQL 8.0.0.
Com_uninstall_component:
Count of UINSTALL COMPONENT statements. Added in MySQL 8.0.0.
Connection_control_delay_generated:
How many times the server delayed a connection request. Added
in MySQL 8.0.1.
Firewall_access_denied:
Number of statements rejected by MySQL Enterprise Firewall.
Added in MySQL 8.0.11.
Firewall_access_granted:
Number of statements accepted by MySQL Enterprise Firewall.
Added in MySQL 8.0.11.
Firewall_cached_entries:
Number of statements recorded by MySQL Enterprise Firewall.
Added in MySQL 8.0.11.
Secondary_engine_execution_count:
For future use. Added in MySQL 8.0.13.
activate_all_roles_on_login:
Whether to activate all user roles at connect time. Added in
MySQL 8.0.2.
admin_address:
IP address to bind to for connections on administrative
interface. Added in MySQL 8.0.14.
admin_port:
TCP/IP number to use for connections on administrative
interface. Added in MySQL 8.0.14.
audit-log:
Whether to activate the audit log plugin. Added in MySQL
8.0.11.
audit_log_buffer_size:
The size of the audit log buffer. Added in MySQL 8.0.11.
audit_log_compression:
Audit log file compression method. Added in MySQL 8.0.11.
audit_log_connection_policy:
Audit logging policy for connection-related events. Added in
MySQL 8.0.11.
audit_log_current_session:
Whether to audit current session. Added in MySQL 8.0.11.
audit_log_encryption:
Audit log file encryption method. Added in MySQL 8.0.11.
audit_log_exclude_accounts:
Accounts not to audit. Added in MySQL 8.0.11.
audit_log_file:
The name of the audit log file. Added in MySQL 8.0.11.
audit_log_filter_id:
ID of current audit log filter. Added in MySQL 8.0.11.
audit_log_flush:
Close and reopen the audit log file. Added in MySQL 8.0.11.
audit_log_format:
The audit log file format. Added in MySQL 8.0.11.
audit_log_include_accounts:
Accounts to audit. Added in MySQL 8.0.11.
audit_log_policy:
Audit logging policy. Added in MySQL 8.0.11.
audit_log_read_buffer_size:
Audit log file read buffer size. Added in MySQL 8.0.11.
audit_log_rotate_on_size:
Close and reopen the audit log file at a certain size. Added
in MySQL 8.0.11.
audit_log_statement_policy:
Audit logging policy for statement-related events. Added in
MySQL 8.0.11.
audit_log_strategy:
The audit logging strategy. Added in MySQL 8.0.11.
authentication_ldap_sasl_auth_method_name:
Authentication method name. Added in MySQL 8.0.11.
authentication_ldap_sasl_bind_base_dn:
LDAP server base distinguished name. Added in MySQL 8.0.11.
authentication_ldap_sasl_bind_root_dn:
LDAP server root distinguished name. Added in MySQL 8.0.11.
authentication_ldap_sasl_bind_root_pwd:
LDAP server root bind password. Added in MySQL 8.0.11.
authentication_ldap_sasl_ca_path:
LDAP server certificate authority file name. Added in MySQL
8.0.11.
authentication_ldap_sasl_group_search_attr:
LDAP server group search attribute. Added in MySQL 8.0.11.
authentication_ldap_sasl_group_search_filter:
LDAP custom group search filter. Added in MySQL 8.0.11.
authentication_ldap_sasl_init_pool_size:
LDAP server initial connection pool size. Added in MySQL
8.0.11.
authentication_ldap_sasl_log_status:
LDAP server log level. Added in MySQL 8.0.11.
authentication_ldap_sasl_max_pool_size:
LDAP server maximum connection pool size. Added in MySQL
8.0.11.
authentication_ldap_sasl_server_host:
LDAP server host name or IP address. Added in MySQL 8.0.11.
authentication_ldap_sasl_server_port:
LDAP server port number. Added in MySQL 8.0.11.
authentication_ldap_sasl_tls:
Whether to use encrypted connections to LDAP server. Added in
MySQL 8.0.11.
authentication_ldap_sasl_user_search_attr:
LDAP server user search attribute. Added in MySQL 8.0.11.
authentication_ldap_simple_auth_method_name:
Authentication method name. Added in MySQL 8.0.11.
authentication_ldap_simple_bind_base_dn:
LDAP server base distinguished name. Added in MySQL 8.0.11.
authentication_ldap_simple_bind_root_dn:
LDAP server root distinguished name. Added in MySQL 8.0.11.
authentication_ldap_simple_bind_root_pwd:
LDAP server root bind password. Added in MySQL 8.0.11.
authentication_ldap_simple_ca_path:
LDAP server certificate authority file name. Added in MySQL
8.0.11.
authentication_ldap_simple_group_search_attr:
LDAP server group search attribute. Added in MySQL 8.0.11.
authentication_ldap_simple_group_search_filter:
LDAP custom group search filter. Added in MySQL 8.0.11.
authentication_ldap_simple_init_pool_size:
LDAP server initial connection pool size. Added in MySQL
8.0.11.
authentication_ldap_simple_log_status:
LDAP server log level. Added in MySQL 8.0.11.
authentication_ldap_simple_max_pool_size:
LDAP server maximum connection pool size. Added in MySQL
8.0.11.
authentication_ldap_simple_server_host:
LDAP server host name or IP address. Added in MySQL 8.0.11.
authentication_ldap_simple_server_port:
LDAP server port number. Added in MySQL 8.0.11.
authentication_ldap_simple_tls:
Whether to use encrypted connections to LDAP server. Added in
MySQL 8.0.11.
authentication_ldap_simple_user_search_attr:
LDAP server user search attribute. Added in MySQL 8.0.11.
authentication_windows_log_level:
Windows authentication plugin logging level. Added in MySQL
8.0.11.
authentication_windows_use_principal_name:
Whether to use Windows authentication plugin principal name.
Added in MySQL 8.0.11.
binlog_encryption:
Enable encryption for binary log files and relay log files on
this server. Added in MySQL 8.0.14.
binlog_expire_logs_seconds:
Purge binary logs after this many seconds. Added in MySQL
8.0.1.
binlog_rotate_encryption_master_key_at_startup:
Rotate the binary log master key at server startup. Added in
MySQL 8.0.14.
binlog_row_event_max_size:
Binary log max event size. Added in MySQL 8.0.14.
binlog_row_metadata:
Configures the amount of table related metadata binary logged
when using row-based logging.. Added in MySQL 8.0.1.
binlog_row_value_options:
Enables binary logging of partial JSON updates for row-based
replication.. Added in MySQL 8.0.3.
binlog_transaction_dependency_history_size:
Number of row hashes kept for looking up transaction that last
updated some row.. Added in MySQL 8.0.1.
binlog_transaction_dependency_tracking:
Source of dependency information (commit timestamps or
transaction write sets) from which to assess which
transactions can be executed in parallel by slave's
multithreaded applier.. Added in MySQL 8.0.1.
caching_sha2_password_auto_generate_rsa_keys:
Whether to autogenerate RSA key-pair files. Added in MySQL
8.0.4.
caching_sha2_password_private_key_path:
SHA2 authentication plugin private key path name. Added in
MySQL 8.0.3.
caching_sha2_password_public_key_path:
SHA2 authentication plugin public key path name. Added in
MySQL 8.0.3.
connection_control_failed_connections_threshold:
Consecutive failed connection attempts before delays occur.
Added in MySQL 8.0.1.
connection_control_max_connection_delay:
Maximum delay (milliseconds) for server response to failed
connection attempts. Added in MySQL 8.0.1.
connection_control_min_connection_delay:
Minimum delay (milliseconds) for server response to failed
connection attempts. Added in MySQL 8.0.1.
create_admin_listener_thread:
Whether to use dedicated listening thread for connections on
administrative interface. Added in MySQL 8.0.14.
cte_max_recursion_depth:
Common table expression maximum recursion depth. Added in
MySQL 8.0.3.
default_collation_for_utf8mb4:
Default collation for utf8mb4 character set. Added in MySQL
8.0.11.
dragnet.Status:
Result of most recent assignment to
dragnet.log_error_filter_rules. Added in MySQL 8.0.12.
dragnet.log_error_filter_rules:
Filter rules for error logging. Added in MySQL 8.0.4.
early-plugin-load:
Specify plugins to load before loading mandatory built-in
plugins and before storage engine initialization. Added in
MySQL 8.0.0.
group_replication_communication_debug_options:
The level of debugging messages for Group Replication
components.. Added in MySQL 8.0.3.
group_replication_consistency:
How the member behaves if it is elected as primary, has a
backlog to process, and a read is requested. Added in MySQL
8.0.14.
group_replication_exit_state_action:
How the instance behaves when it leaves the group
involuntarily. Added in MySQL 8.0.12.
group_replication_flow_control_hold_percent:
Defines what percentage of the group quota remains unused.
Added in MySQL 8.0.2.
group_replication_flow_control_max_commit_quota:
Defines the maximum flow control quota of the group. Added in
MySQL 8.0.2.
group_replication_flow_control_member_quota_percent:
Defines the percentage of the quota that a member should
assume is available for itself when calculating the quotas.
Added in MySQL 8.0.2.
group_replication_flow_control_min_quota:
Controls the lowest flow control quota that can be assigned to
a member. Added in MySQL 8.0.2.
group_replication_flow_control_min_recovery_quota:
Controls the lowest quota that can be assigned to a member
because of another recovering member in the group. Added in
MySQL 8.0.2.
group_replication_flow_control_period:
Defines how many seconds to wait between flow control
iterations. Added in MySQL 8.0.2.
group_replication_flow_control_release_percent:
Defines how the group quota should be released when flow
control no longer needs to throttle the writer members. Added
in MySQL 8.0.2.
group_replication_member_expel_timeout:
The time between a suspected failure of a group member and it
being expelled from the group, causing a group membership
reconfiguration.. Added in MySQL 8.0.13.
group_replication_member_weight:
Chance of this member being elected as primary. Added in MySQL
8.0.2.
group_replication_recovery_get_public_key:
Whether to accept preference about fetching public key from
master. Added in MySQL 8.0.4.
group_replication_recovery_public_key_path:
To accept public key information. Added in MySQL 8.0.4.
group_replication_unreachable_majority_timeout:
How long to wait for network partitions that result in a
minority to leave the group. Added in MySQL 8.0.2.
histogram_generation_max_mem_size:
Maximum memory for creating histogram statistics. Added in
MySQL 8.0.2.
immediate_server_version:
The MySQL Server release number of the server that is the
immediate master in a replication topology. Added in MySQL
8.0.14.
information_schema_stats_expiry:
Expiration setting for cached table statistics. Added in MySQL
8.0.3.
innodb_buffer_pool_debug:
Permits multiple buffer pool instances when the buffer pool is
less than 1GB in size. Added in MySQL 8.0.0.
innodb_buffer_pool_in_core_file:
Controls writing of buffer pool pages to core files. Added in
MySQL 8.0.14.
innodb_checkpoint_disabled:
Disables checkpoints so that a deliberate server exit always
initiates recovery. Added in MySQL 8.0.2.
innodb_ddl_log_crash_reset_debug:
A debug option that resets DDL log crash injection counters.
Added in MySQL 8.0.3.
innodb_deadlock_detect:
Enables or disables deadlock detection. Added in MySQL 8.0.0.
innodb_dedicated_server:
Enables automatic configuration of buffer pool size, log file
size, and flush method. Added in MySQL 8.0.3.
innodb_directories:
Defines directories to scan at startup for tablespace data
files. Added in MySQL 8.0.4.
innodb_fsync_threshold:
Controls how often InnoDB calls fsync when creating a new
file. Added in MySQL 8.0.13.
innodb_log_checkpoint_fuzzy_now:
A debug option that forces InnoDB to write a fuzzy checkpoint.
Added in MySQL 8.0.13.
innodb_log_spin_cpu_abs_lwm:
Minimum amount of CPU usage below which user threads no longer
spin while waiting for flushed redo. Added in MySQL 8.0.11.
innodb_log_spin_cpu_pct_hwm:
Maximum amount of CPU usage above which user threads no longer
spin while waiting for flushed redo. Added in MySQL 8.0.11.
innodb_log_wait_for_flush_spin_hwm:
The maximum average log flush time beyond which user threads
no longer spin while waiting for flushed redo. Added in MySQL
8.0.11.
innodb_print_ddl_logs:
Whether or not to print DDL logs to the error log. Added in
MySQL 8.0.3.
innodb_redo_log_encrypt:
Controls encryption of redo log data for encrypted tablepaces.
Added in MySQL 8.0.1.
innodb_scan_directories:
Defines directories to scan for tablespace files during InnoDB
recovery. Added in MySQL 8.0.2.
innodb_stats_include_delete_marked:
Include delete-marked records when calculating persistent
InnoDB statistics. Added in MySQL 8.0.1.
innodb_temp_tablespaces_dir:
Session temporary tablespaces path. Added in MySQL 8.0.13.
innodb_tmpdir:
The directory location for the temporary table files created
during online ALTER TABLE operations. Added in MySQL 8.0.0.
innodb_undo_log_encrypt:
Controls encryption of undo log data for encrypted tablepaces.
Added in MySQL 8.0.1.
internal_tmp_mem_storage_engine:
Defines the storage to use for internal in-memory temporary
tables. Added in MySQL 8.0.2.
keyring-migration-destination:
Key migration destination keyring plugin. Added in MySQL
8.0.4.
keyring-migration-host:
Host name for connecting to running server for key migration.
Added in MySQL 8.0.4.
keyring-migration-password:
Password for connecting to running server for key migration.
Added in MySQL 8.0.4.
keyring-migration-port:
TCP/IP port number for connecting to running server for key
migration. Added in MySQL 8.0.4.
keyring-migration-socket:
Unix socket file or Windows named pipe for connecting to
running server for key migration. Added in MySQL 8.0.4.
keyring-migration-source:
Key migration source keyring plugin. Added in MySQL 8.0.4.
keyring-migration-user:
User name for connecting to running server for key migration.
Added in MySQL 8.0.4.
keyring_aws_cmk_id:
AWS keyring plugin customer master key ID value. Added in
MySQL 8.0.11.
keyring_aws_conf_file:
AWS keyring plugin configuration file location. Added in MySQL
8.0.11.
keyring_aws_data_file:
AWS keyring plugin storage file location. Added in MySQL
8.0.11.
keyring_aws_region:
AWS keyring plugin region. Added in MySQL 8.0.11.
keyring_encrypted_file_data:
keyring_encrypted_file plugin data file. Added in MySQL
8.0.11.
keyring_encrypted_file_password:
keyring_encrypted_file plugin password. Added in MySQL 8.0.11.
keyring_okv_conf_dir:
Oracle Key Vault keyring plugin configuration directory. Added
in MySQL 8.0.11.
keyring_operations:
Whether keyring operations are enabled. Added in MySQL 8.0.4.
log_error_filter_rules:
Filter rules for error logging. Added in MySQL 8.0.2.
log_error_services:
Components to use for error logging. Added in MySQL 8.0.2.
log_error_suppression_list:
Warning/information error log messages to suppress. Added in
MySQL 8.0.13.
log_slow_extra:
Whether to write extra information to the slow query log file.
Added in MySQL 8.0.14.
mandatory_roles:
Automatically granted roles for all users. Added in MySQL
8.0.2.
mysql_firewall_mode:
Whether MySQL Enterprise Firewall is operational. Added in
MySQL 8.0.11.
mysql_firewall_trace:
Whether to enable firewall trace. Added in MySQL 8.0.11.
mysqlx:
Whether X Plugin is initialized. Added in MySQL 8.0.11.
mysqlx-interactive-timeout:
Number of seconds to wait for an interactive client to
timeout. Added in MySQL 8.0.4.
mysqlx-port-read-timeout:
Number of seconds to wait for blocking read operations to
complete. Added in MySQL 8.0.4.
mysqlx-wait-timeout:
Number of seconds to wait for activity on a connection. Added
in MySQL 8.0.4.
mysqlx-write-timeout:
Number of seconds to wait for blocking write operation to
complete. Added in MySQL 8.0.4.
mysqlx_interactive_timeout:
Number of seconds to wait for an interactive client to
timeout. Added in MySQL 8.0.4.
mysqlx_read_timeout:
Number of seconds to wait for blocking read operations to
complete. Added in MySQL 8.0.4.
mysqlx_wait_timeout:
Number of seconds to wait for activity on a connection. Added
in MySQL 8.0.4.
mysqlx_write_timeout:
Number of seconds to wait for blocking write operation to
complete. Added in MySQL 8.0.4.
named_pipe_full_access_group:
Name of Windows group granted full access to the named pipe.
Added in MySQL 8.0.14.
no-dd-upgrade:
Prevents the automatic upgrade of data dictionary table
definitions at startup. Added in MySQL 8.0.4.
no-monitor:
Do not fork monitor process required for RESTART. Added in
MySQL 8.0.12.
original_commit_timestamp:
The time when a transaction was committed on the original
master. Added in MySQL 8.0.1.
original_server_version:
The MySQL Server release number of the server where a
transaction was originally committed. Added in MySQL 8.0.14.
password_history:
Number of password changes required before password reuse.
Added in MySQL 8.0.3.
password_require_current:
Whether password changes require current password
verification. Added in MySQL 8.0.13.
password_reuse_interval:
Number of days elapsed required before password reuse. Added
in MySQL 8.0.3.
performance_schema_max_digest_sample_age:
The query resample age in seconds. Added in MySQL 8.0.3.
persist_only_admin_x509_subject:
SSL certificate X.509 Subject that enables persisting
persist-restricted system variables. Added in MySQL 8.0.14.
persisted_globals_load:
Whether to load persisted configuration settings. Added in
MySQL 8.0.0.
regexp_stack_limit:
Regular expression match stack size limit. Added in MySQL
8.0.4.
regexp_time_limit:
Regular expression match timeout. Added in MySQL 8.0.4.
resultset_metadata:
Whether the server returns result set metadata. Added in MySQL
8.0.3.
rpl_read_size:
Set the minimum amount of data in bytes that is read from the
binary log files and relay log files. Added in MySQL 8.0.11.
show_create_table_verbosity:
Whether to display ROW_FORMAT in SHOW CREATE TABLE even if it
has the default value. Added in MySQL 8.0.11.
sql_require_primary_key:
Whether tables must have a primary key. Added in MySQL 8.0.13.
ssl_fips_mode:
Whether to enable FIPS mode on the server side. Added in MySQL
8.0.11.
syseventlog.facility:
Facility for syslog messages. Added in MySQL 8.0.13.
syseventlog.include_pid:
Whether to include server PID in syslog messages. Added in
MySQL 8.0.13.
syseventlog.tag:
Tag for server identifier in syslog messages. Added in MySQL
8.0.13.
temptable_max_ram:
Defines the maximum amount of memory that can occupied by the
TempTable storage engine before data is stored on disk. Added
in MySQL 8.0.2.
thread_pool_algorithm:
The thread pool algorithm. Added in MySQL 8.0.11.
thread_pool_high_priority_connection:
Whether the current session is high priority. Added in MySQL
8.0.11.
thread_pool_max_unused_threads:
The maximum permitted number of unused threads. Added in MySQL
8.0.11.
thread_pool_prio_kickup_timer:
How long before a statement is moved to high-priority
execution. Added in MySQL 8.0.11.
thread_pool_size:
Number of thread groups in the thread pool. Added in MySQL
8.0.11.
thread_pool_stall_limit:
How long before a statement is defined as stalled. Added in
MySQL 8.0.11.
use_secondary_engine:
For future use. Added in MySQL 8.0.13.
validate-config:
Validate server configuration. Added in MySQL 8.0.15.
validate_password.check_user_name:
Whether to check passwords against user name. Added in MySQL
8.0.4.
validate_password.dictionary_file:
validate_password dictionary file. Added in MySQL 8.0.4.
validate_password.dictionary_file_last_parsed:
When the dictionary file was last parsed. Added in MySQL
8.0.4.
validate_password.dictionary_file_words_count:
Number of words in dictionary file. Added in MySQL 8.0.4.
validate_password.length:
validate_password required password length. Added in MySQL
8.0.4.
validate_password.mixed_case_count:
validate_password required number of uppercase/lowercase
characters. Added in MySQL 8.0.4.
validate_password.number_count:
validate_password required number of digit characters. Added
in MySQL 8.0.4.
validate_password.policy:
validate_password password policy. Added in MySQL 8.0.4.
validate_password.special_char_count:
validate_password required number of special characters. Added
in MySQL 8.0.4.
version_compile_zlib:
Version of compiled-in zlib library. Added in MySQL 8.0.11.
windowing_use_high_precision:
Whether to compute window functions to high precision. Added
in MySQL 8.0.2.
The following system variables, status variables, and options have been deprecated in MySQL 8.0.
expire_logs_days:
Purge binary logs after this many days. Deprecated as of MySQL
8.0.3.
innodb_undo_tablespaces:
The number of tablespace files that rollback segments are
divided between. Deprecated as of MySQL 8.0.4.
log_syslog:
Whether to write error log to syslog. Deprecated as of MySQL
8.0.2.
symbolic-links:
Permit symbolic links for MyISAM tables. Deprecated as of
MySQL 8.0.2.
The following system variables, status variables, and options have been removed in MySQL 8.0.
Com_alter_db_upgrade:
Count of ALTER DATABASE ... UPGRADE DATA DIRECTORY NAME
statements. Removed in MySQL 8.0.0.
Innodb_available_undo_logs:
Display the total number of InnoDB rollback segments;
different from innodb_rollback_segments, which displays the
number of active rollback segments. Removed in MySQL 8.0.2.
Qcache_free_blocks:
Number of free memory blocks in the query cache. Removed in
MySQL 8.0.3.
Qcache_free_memory:
The amount of free memory for the query cache. Removed in
MySQL 8.0.3.
Qcache_hits:
Number of query cache hits. Removed in MySQL 8.0.3.
Qcache_inserts:
Number of query cache inserts. Removed in MySQL 8.0.3.
Qcache_lowmem_prunes:
Number of queries that were deleted from the query cache due
to lack of free memory in the cache. Removed in MySQL 8.0.3.
Qcache_not_cached:
Number of noncached queries (not cacheable, or not cached due
to the query_cache_type setting). Removed in MySQL 8.0.3.
Qcache_queries_in_cache:
Number of queries registered in the query cache. Removed in
MySQL 8.0.3.
Qcache_total_blocks:
The total number of blocks in the query cache. Removed in
MySQL 8.0.3.
Slave_heartbeat_period:
The slave's replication heartbeat interval, in seconds.
Removed in MySQL 8.0.1.
Slave_last_heartbeat:
Shows when the latest heartbeat signal was received, in
TIMESTAMP format. Removed in MySQL 8.0.1.
Slave_received_heartbeats:
Number of heartbeats received by a replication slave since
previous reset. Removed in MySQL 8.0.1.
Slave_retried_transactions:
The total number of times since startup that the replication
slave SQL thread has retried transactions. Removed in MySQL
8.0.1.
Slave_running:
The state of this server as a replication slave (slave I/O
thread status). Removed in MySQL 8.0.1.
bootstrap:
Used by mysql installation scripts. Removed in MySQL 8.0.0.
date_format:
The DATE format (unused). Removed in MySQL 8.0.3.
datetime_format:
The DATETIME/TIMESTAMP format (unused). Removed in MySQL
8.0.3.
des-key-file:
Load keys for des_encrypt() and des_encrypt from given file.
Removed in MySQL 8.0.3.
group_replication_allow_local_disjoint_gtids_join:
Allow the current server to join the group even if it has
transactions not present in the group. Removed in MySQL 8.0.4.
have_crypt:
Availability of the crypt() system call. Removed in MySQL
8.0.3.
ignore-builtin-innodb:
Ignore the built-in InnoDB. Removed in MySQL 8.0.3.
ignore-db-dir:
Treat directory as nondatabase directory. Removed in MySQL
8.0.0.
ignore_db_dirs:
Directories treated as nondatabase directories. Removed in
MySQL 8.0.0.
innodb_checksums:
Enable InnoDB checksums validation. Removed in MySQL 8.0.0.
innodb_disable_resize_buffer_pool_debug:
Disables resizing of the InnoDB buffer pool. Removed in MySQL
8.0.0.
innodb_file_format:
The format for new InnoDB tables. Removed in MySQL 8.0.0.
innodb_file_format_check:
Whether InnoDB performs file format compatibility checking.
Removed in MySQL 8.0.0.
innodb_file_format_max:
The file format tag in the shared tablespace. Removed in MySQL
8.0.0.
innodb_large_prefix:
Enables longer keys for column prefix indexes. Removed in
MySQL 8.0.0.
innodb_locks_unsafe_for_binlog:
Force InnoDB not to use next-key locking. Instead use only
row-level locking. Removed in MySQL 8.0.0.
innodb_stats_sample_pages:
Number of index pages to sample for index distribution
statistics. Removed in MySQL 8.0.0.
innodb_support_xa:
Enable InnoDB support for the XA two-phase commit. Removed in
MySQL 8.0.0.
innodb_undo_logs:
Defines the number of undo logs (rollback segments) used by
InnoDB; an alias for innodb_rollback_segments. Removed in
MySQL 8.0.2.
log-warnings:
Log some noncritical warnings to the log file. Removed in
MySQL 8.0.3.
log_builtin_as_identified_by_password:
Whether to log CREATE/ALTER USER, GRANT in backward-compatible
fashion. Removed in MySQL 8.0.11.
log_error_filter_rules:
Filter rules for error logging. Removed in MySQL 8.0.4.
log_syslog:
Whether to write error log to syslog. Removed in MySQL 8.0.13.
log_syslog_facility:
Facility for syslog messages. Removed in MySQL 8.0.13.
log_syslog_include_pid:
Whether to include server PID in syslog messages. Removed in
MySQL 8.0.13.
log_syslog_tag:
Tag for server identifier in syslog messages. Removed in MySQL
8.0.13.
max_tmp_tables:
Unused. Removed in MySQL 8.0.3.
metadata_locks_cache_size:
Size of the metadata locks cache. Removed in MySQL 8.0.13.
metadata_locks_hash_instances:
Number of metadata lock hashes. Removed in MySQL 8.0.13.
multi_range_count:
The maximum number of ranges to send to a table handler at
once during range selects. Removed in MySQL 8.0.3.
old_passwords:
Selects password hashing method for PASSWORD(). Removed in
MySQL 8.0.11.
partition:
Enable (or disable) partitioning support. Removed in MySQL
8.0.0.
query_cache_limit:
Do not cache results that are bigger than this. Removed in
MySQL 8.0.3.
query_cache_min_res_unit:
Minimal size of unit in which space for results is allocated
(last unit will be trimmed after writing all result data).
Removed in MySQL 8.0.3.
query_cache_size:
The memory allocated to store results from old queries.
Removed in MySQL 8.0.3.
query_cache_type:
Query cache type. Removed in MySQL 8.0.3.
query_cache_wlock_invalidate:
Invalidate queries in query cache on LOCK for write. Removed
in MySQL 8.0.3.
secure-auth:
Disallow authentication for accounts that have old (pre-4.1)
passwords. Removed in MySQL 8.0.3.
show_compatibility_56:
Compatibility for SHOW STATUS/VARIABLES. Removed in MySQL
8.0.1.
skip-partition:
Do not enable user-defined partitioning. Removed in MySQL
8.0.0.
sync_frm:
Sync .frm to disk on create. Enabled by default. Removed in
MySQL 8.0.0.
temp-pool:
Using this option will cause most temporary files created to
use a small set of names, rather than a unique name for each
new file. Removed in MySQL 8.0.1.
time_format:
The TIME format (unused). Removed in MySQL 8.0.3.
tx_isolation:
The default transaction isolation level. Removed in MySQL
8.0.3.
tx_read_only:
Default transaction access mode. Removed in MySQL 8.0.3.
This section lists sources of additional information that you may find helpful, such as MySQL websites, mailing lists, user forums, and Internet Relay Chat.
The primary website for MySQL documentation is https://dev.mysql.com/doc/. Online and downloadable documentation formats are available for the MySQL Reference Manual, MySQL Connectors, and more.
The MySQL developers provide information about new and upcoming features as the MySQL Server Blog.
This section introduces the MySQL mailing lists and provides guidelines as to how the lists should be used. When you subscribe to a mailing list, you receive all postings to the list as email messages. You can also send your own questions and answers to the list.
To subscribe to or unsubscribe from any of the mailing lists described in this section, visit http://lists.mysql.com/. For most of them, you can select the regular version of the list where you get individual messages, or a digest version where you get one large message per day.
Please do not send messages about subscribing or unsubscribing to any of the mailing lists, because such messages are distributed automatically to thousands of other users.
Your local site may have many subscribers to a MySQL mailing list.
If so, the site may have a local mailing list, so that messages
sent from lists.mysql.com to your site are
propagated to the local list. In such cases, please contact your
system administrator to be added to or dropped from the local
MySQL list.
To have traffic for a mailing list go to a separate mailbox in
your mail program, set up a filter based on the message headers.
You can use either the List-ID: or
Delivered-To: headers to identify list
messages.
The MySQL mailing lists are as follows:
announce
The list for announcements of new versions of MySQL and related programs. This is a low-volume list to which all MySQL users should subscribe.
mysql
The main list for general MySQL discussion. Please note that some topics are better discussed on the more-specialized lists. If you post to the wrong list, you may not get an answer.
bugs
The list for people who want to stay informed about issues reported since the last release of MySQL or who want to be actively involved in the process of bug hunting and fixing. See Section 1.7, “How to Report Bugs or Problems”.
internals
The list for people who work on the MySQL code. This is also the forum for discussions on MySQL development and for posting patches.
mysqldoc
The list for people who work on the MySQL documentation.
benchmarks
The list for anyone interested in performance issues. Discussions concentrate on database performance (not limited to MySQL), but also include broader categories such as performance of the kernel, file system, disk system, and so on.
packagers
The list for discussions on packaging and distributing MySQL. This is the forum used by distribution maintainers to exchange ideas on packaging MySQL and on ensuring that MySQL looks and feels as similar as possible on all supported platforms and operating systems.
java
The list for discussions about the MySQL server and Java. It is mostly used to discuss JDBC drivers such as MySQL Connector/J.
win32
The list for all topics concerning the MySQL software on Microsoft operating systems, such as Windows 9x, Me, NT, 2000, XP, and 2003.
myodbc
The list for all topics concerning connecting to the MySQL server with ODBC.
gui-tools
The list for all topics concerning MySQL graphical user interface tools such as MySQL Workbench.
cluster
The list for discussion of MySQL Cluster.
dotnet
The list for discussion of the MySQL server and the .NET platform. It is mostly related to MySQL Connector/NET.
plusplus
The list for all topics concerning programming with the C++ API for MySQL.
perl
The list for all topics concerning Perl support for MySQL with
DBD::mysql.
If you're unable to get an answer to your questions from a MySQL mailing list or forum, one option is to purchase support from Oracle. This puts you in direct contact with MySQL developers.
The following MySQL mailing lists are in languages other than English. These lists are not operated by Oracle.
A French mailing list.
A Korean mailing list. To subscribe, email subscribe
mysql [email protected] to this list.
A German mailing list. To subscribe, email subscribe
mysql-de [email protected] to this list. You can
find information about this mailing list at
http://www.4t2.com/mysql/.
A Portuguese mailing list. To subscribe, email
subscribe mysql-br [email protected] to
this list.
A Spanish mailing list. To subscribe, email subscribe
mysql [email protected] to this list.
Please do not post mail messages from your browser with HTML mode turned on. Many users do not read mail with a browser.
When you answer a question sent to a mailing list, if you consider your answer to have broad interest, you may want to post it to the list instead of replying directly to the individual who asked. Try to make your answer general enough that people other than the original poster may benefit from it. When you post to the list, please make sure that your answer is not a duplication of a previous answer.
Try to summarize the essential part of the question in your reply. Do not feel obliged to quote the entire original message.
When answers are sent to you individually and not to the mailing list, it is considered good etiquette to summarize the answers and send the summary to the mailing list so that others may have the benefit of responses you received that helped you solve your problem.
The forums at http://forums.mysql.com are an important community resource. Many forums are available, grouped into these general categories:
Migration
MySQL Usage
MySQL Connectors
Programming Languages
Tools
3rd-Party Applications
Storage Engines
MySQL Technology
SQL Standards
Business
In addition to the various MySQL mailing lists and forums, you can find experienced community people on Internet Relay Chat (IRC). These are the best networks/channels currently known to us:
freenode (see http://www.freenode.net/ for servers)
#mysql is primarily for MySQL questions,
but other database and general SQL questions are welcome.
Questions about PHP, Perl, or C in combination with MySQL are
also common.
#workbench is primarily for MySQL Workbench
related questions and thoughts, and it is also a good place to
meet the MySQL Workbench developers.
Oracle offers technical support in the form of MySQL Enterprise. For organizations that rely on the MySQL DBMS for business-critical production applications, MySQL Enterprise is a commercial subscription offering which includes:
MySQL Enterprise Server
MySQL Enterprise Monitor
Monthly Rapid Updates and Quarterly Service Packs
MySQL Knowledge Base
24x7 Technical and Consultative Support
MySQL Enterprise is available in multiple tiers, giving you the flexibility to choose the level of service that best matches your needs. For more information, see MySQL Enterprise.
Before posting a bug report about a problem, please try to verify that it is a bug and that it has not been reported already:
Start by searching the MySQL online manual at https://dev.mysql.com/doc/. We try to keep the manual up to date by updating it frequently with solutions to newly found problems. In addition, the release notes accompanying the manual can be particularly useful since it is quite possible that a newer version contains a solution to your problem. The release notes are available at the location just given for the manual.
If you get a parse error for an SQL statement, please check your syntax closely. If you cannot find something wrong with it, it is extremely likely that your current version of MySQL Server doesn't support the syntax you are using. If you are using the current version and the manual doesn't cover the syntax that you are using, MySQL Server doesn't support your statement.
If the manual covers the syntax you are using, but you have an older version of MySQL Server, you should check the MySQL change history to see when the syntax was implemented. In this case, you have the option of upgrading to a newer version of MySQL Server.
For solutions to some common problems, see Section B.6, “Problems and Common Errors”.
Search the bugs database at http://bugs.mysql.com/ to see whether the bug has been reported and fixed.
Search the MySQL mailing list archives at http://lists.mysql.com/. See Section 1.6.2, “MySQL Mailing Lists”.
You can also use http://www.mysql.com/search/ to search all the Web pages (including the manual) that are located at the MySQL website.
If you cannot find an answer in the manual, the bugs database, or the mailing list archives, check with your local MySQL expert. If you still cannot find an answer to your question, please use the following guidelines for reporting the bug.
The normal way to report bugs is to visit http://bugs.mysql.com/, which is the address for our bugs database. This database is public and can be browsed and searched by anyone. If you log in to the system, you can enter new reports.
Bugs posted in the bugs database at http://bugs.mysql.com/ that are corrected for a given release are noted in the release notes.
If you find a sensitive security bug in MySQL Server, please let us
know immediately by sending an email message to
<[email protected]>. Exception: Support customers
should report all problems, including security bugs, to Oracle
Support at http://support.oracle.com/.
To discuss problems with other users, you can use one of the MySQL mailing lists. Section 1.6.2, “MySQL Mailing Lists”.
Writing a good bug report takes patience, but doing it right the first time saves time both for us and for yourself. A good bug report, containing a full test case for the bug, makes it very likely that we will fix the bug in the next release. This section helps you write your report correctly so that you do not waste your time doing things that may not help us much or at all. Please read this section carefully and make sure that all the information described here is included in your report.
Preferably, you should test the problem using the latest production
or development version of MySQL Server before posting. Anyone should
be able to repeat the bug by just using mysql test <
script_file on your test case or by running the shell or
Perl script that you include in the bug report. Any bug that we are
able to repeat has a high chance of being fixed in the next MySQL
release.
It is most helpful when a good description of the problem is included in the bug report. That is, give a good example of everything you did that led to the problem and describe, in exact detail, the problem itself. The best reports are those that include a full example showing how to reproduce the bug or problem. See Section 29.5, “Debugging and Porting MySQL”.
Remember that it is possible for us to respond to a report containing too much information, but not to one containing too little. People often omit facts because they think they know the cause of a problem and assume that some details do not matter. A good principle to follow is that if you are in doubt about stating something, state it. It is faster and less troublesome to write a couple more lines in your report than to wait longer for the answer if we must ask you to provide information that was missing from the initial report.
The most common errors made in bug reports are (a) not including the version number of the MySQL distribution that you use, and (b) not fully describing the platform on which the MySQL server is installed (including the platform type and version number). These are highly relevant pieces of information, and in 99 cases out of 100, the bug report is useless without them. Very often we get questions like, “Why doesn't this work for me?” Then we find that the feature requested wasn't implemented in that MySQL version, or that a bug described in a report has been fixed in newer MySQL versions. Errors often are platform-dependent. In such cases, it is next to impossible for us to fix anything without knowing the operating system and the version number of the platform.
If you compiled MySQL from source, remember also to provide information about your compiler if it is related to the problem. Often people find bugs in compilers and think the problem is MySQL-related. Most compilers are under development all the time and become better version by version. To determine whether your problem depends on your compiler, we need to know what compiler you used. Note that every compiling problem should be regarded as a bug and reported accordingly.
If a program produces an error message, it is very important to include the message in your report. If we try to search for something from the archives, it is better that the error message reported exactly matches the one that the program produces. (Even the lettercase should be observed.) It is best to copy and paste the entire error message into your report. You should never try to reproduce the message from memory.
If you have a problem with Connector/ODBC (MyODBC), please try to generate a trace file and send it with your report. See How to Report Connector/ODBC Problems or Bugs.
If your report includes long query output lines from test cases that
you run with the mysql command-line tool, you can
make the output more readable by using the
--vertical option or the
\G statement terminator. The
EXPLAIN SELECT
example later in this section demonstrates the use of
\G.
Please include the following information in your report:
The version number of the MySQL distribution you are using (for
example, MySQL 5.7.10). You can find out which version you are
running by executing mysqladmin version. The
mysqladmin program can be found in the
bin directory under your MySQL installation
directory.
The manufacturer and model of the machine on which you experience the problem.
The operating system name and version. If you work with Windows,
you can usually get the name and version number by
double-clicking your My Computer icon and pulling down the
“Help/About Windows” menu. For most Unix-like
operating systems, you can get this information by executing the
command uname -a.
Sometimes the amount of memory (real and virtual) is relevant. If in doubt, include these values.
The contents of the docs/INFO_BIN file from
your MySQL installation. This file contains information about
how MySQL was configured and compiled.
If you are using a source distribution of the MySQL software, include the name and version number of the compiler that you used. If you have a binary distribution, include the distribution name.
If the problem occurs during compilation, include the exact error messages and also a few lines of context around the offending code in the file where the error occurs.
If mysqld died, you should also report the statement that crashed mysqld. You can usually get this information by running mysqld with query logging enabled, and then looking in the log after mysqld crashes. See Section 29.5, “Debugging and Porting MySQL”.
If a database table is related to the problem, include the
output from the SHOW CREATE TABLE
statement in the bug report. This is a very easy way to get the
definition of any table in a database. The information helps us
create a situation matching the one that you have experienced.
db_name.tbl_name
The SQL mode in effect when the problem occurred can be
significant, so please report the value of the
sql_mode system variable. For
stored procedure, stored function, and trigger objects, the
relevant sql_mode value is the
one in effect when the object was created. For a stored
procedure or function, the SHOW CREATE
PROCEDURE or SHOW CREATE
FUNCTION statement shows the relevant SQL mode, or you
can query INFORMATION_SCHEMA for the
information:
SELECT ROUTINE_SCHEMA, ROUTINE_NAME, SQL_MODE FROM INFORMATION_SCHEMA.ROUTINES;
For triggers, you can use this statement:
SELECT EVENT_OBJECT_SCHEMA, EVENT_OBJECT_TABLE, TRIGGER_NAME, SQL_MODE FROM INFORMATION_SCHEMA.TRIGGERS;
For performance-related bugs or problems with
SELECT statements, you should
always include the output of EXPLAIN SELECT
..., and at least the number of rows that the
SELECT statement produces. You
should also include the output from SHOW CREATE TABLE
for each table
that is involved. The more information you provide about your
situation, the more likely it is that someone can help you.
tbl_name
The following is an example of a very good bug report. The
statements are run using the mysql
command-line tool. Note the use of the \G
statement terminator for statements that would otherwise provide
very long output lines that are difficult to read.
mysql>SHOW VARIABLES;mysql>SHOW COLUMNS FROM ...\G<output from SHOW COLUMNS>mysql>EXPLAIN SELECT ...\G<output from EXPLAIN>mysql>FLUSH STATUS;mysql>SELECT ...;<A short version of the output from SELECT, including the time taken to run the query>mysql>SHOW STATUS;<output from SHOW STATUS>
If a bug or problem occurs while running mysqld, try to provide an input script that reproduces the anomaly. This script should include any necessary source files. The more closely the script can reproduce your situation, the better. If you can make a reproducible test case, you should upload it to be attached to the bug report.
If you cannot provide a script, you should at least include the output from mysqladmin variables extended-status processlist in your report to provide some information on how your system is performing.
If you cannot produce a test case with only a few rows, or if
the test table is too big to be included in the bug report (more
than 10 rows), you should dump your tables using
mysqldump and create a
README file that describes your problem.
Create a compressed archive of your files using
tar and gzip or
zip. After you initiate a bug report for our
bugs database at http://bugs.mysql.com/, click
the Files tab in the bug report for instructions on uploading
the archive to the bugs database.
If you believe that the MySQL server produces a strange result from a statement, include not only the result, but also your opinion of what the result should be, and an explanation describing the basis for your opinion.
When you provide an example of the problem, it is better to use the table names, variable names, and so forth that exist in your actual situation than to come up with new names. The problem could be related to the name of a table or variable. These cases are rare, perhaps, but it is better to be safe than sorry. After all, it should be easier for you to provide an example that uses your actual situation, and it is by all means better for us. If you have data that you do not want to be visible to others in the bug report, you can upload it using the Files tab as previously described. If the information is really top secret and you do not want to show it even to us, go ahead and provide an example using other names, but please regard this as the last choice.
Include all the options given to the relevant programs, if
possible. For example, indicate the options that you use when
you start the mysqld server, as well as the
options that you use to run any MySQL client programs. The
options to programs such as mysqld and
mysql, and to the
configure script, are often key to resolving
problems and are very relevant. It is never a bad idea to
include them. If your problem involves a program written in a
language such as Perl or PHP, please include the language
processor's version number, as well as the version for any
modules that the program uses. For example, if you have a Perl
script that uses the DBI and
DBD::mysql modules, include the version
numbers for Perl, DBI, and
DBD::mysql.
If your question is related to the privilege system, please include the output of mysqladmin reload, and all the error messages you get when trying to connect. When you test your privileges, you should execute mysqladmin reload version and try to connect with the program that gives you trouble.
If you have a patch for a bug, do include it. But do not assume that the patch is all we need, or that we can use it, if you do not provide some necessary information such as test cases showing the bug that your patch fixes. We might find problems with your patch or we might not understand it at all. If so, we cannot use it.
If we cannot verify the exact purpose of the patch, we will not use it. Test cases help us here. Show that the patch handles all the situations that may occur. If we find a borderline case (even a rare one) where the patch will not work, it may be useless.
Guesses about what the bug is, why it occurs, or what it depends on are usually wrong. Even the MySQL team cannot guess such things without first using a debugger to determine the real cause of a bug.
Indicate in your bug report that you have checked the reference manual and mail archive so that others know you have tried to solve the problem yourself.
If your data appears corrupt or you get errors when you access a
particular table, first check your tables with
CHECK TABLE. If that statement
reports any errors:
The InnoDB crash recovery mechanism
handles cleanup when the server is restarted after being
killed, so in typical operation there is no need to
“repair” tables. If you encounter an error with
InnoDB tables, restart the server and see
whether the problem persists, or whether the error affected
only cached data in memory. If data is corrupted on disk,
consider restarting with the
innodb_force_recovery
option enabled so that you can dump the affected tables.
For non-transactional tables, try to repair them with
REPAIR TABLE or with
myisamchk. See
Chapter 5, MySQL Server Administration.
If you are running Windows, please verify the value of
lower_case_table_names using
the SHOW VARIABLES LIKE
'lower_case_table_names' statement. This variable
affects how the server handles lettercase of database and table
names. Its effect for a given value should be as described in
Section 9.2.2, “Identifier Case Sensitivity”.
If you often get corrupted tables, you should try to find out
when and why this happens. In this case, the error log in the
MySQL data directory may contain some information about what
happened. (This is the file with the .err
suffix in the name.) See Section 5.4.2, “The Error Log”. Please
include any relevant information from this file in your bug
report. Normally mysqld should
never crash a table if nothing killed it in
the middle of an update. If you can find the cause of
mysqld dying, it is much easier for us to
provide you with a fix for the problem. See
Section B.6.1, “How to Determine What Is Causing a Problem”.
If possible, download and install the most recent version of MySQL Server and check whether it solves your problem. All versions of the MySQL software are thoroughly tested and should work without problems. We believe in making everything as backward-compatible as possible, and you should be able to switch MySQL versions without difficulty. See Section 2.1.1, “Which MySQL Version and Distribution to Install”.
This section describes how MySQL relates to the ANSI/ISO SQL standards. MySQL Server has many extensions to the SQL standard, and here you can find out what they are and how to use them. You can also find information about functionality missing from MySQL Server, and how to work around some of the differences.
The SQL standard has been evolving since 1986 and several versions exist. In this manual, “SQL-92” refers to the standard released in 1992. “SQL:1999”, “SQL:2003”, “SQL:2008”, and “SQL:2011” refer to the versions of the standard released in the corresponding years, with the last being the most recent version. We use the phrase “the SQL standard” or “standard SQL” to mean the current version of the SQL Standard at any time.
One of our main goals with the product is to continue to work
toward compliance with the SQL standard, but without sacrificing
speed or reliability. We are not afraid to add extensions to SQL
or support for non-SQL features if this greatly increases the
usability of MySQL Server for a large segment of our user base.
The HANDLER interface is an example
of this strategy. See Section 13.2.4, “HANDLER Syntax”.
We continue to support transactional and nontransactional databases to satisfy both mission-critical 24/7 usage and heavy Web or logging usage.
MySQL Server was originally designed to work with medium-sized databases (10-100 million rows, or about 100MB per table) on small computer systems. Today MySQL Server handles terabyte-sized databases.
We are not targeting real-time support, although MySQL replication capabilities offer significant functionality.
MySQL supports ODBC levels 0 to 3.51.
MySQL supports high-availability database clustering using the
NDBCLUSTER storage engine. See
Chapter 22, MySQL NDB Cluster 8.0.
We implement XML functionality which supports most of the W3C XPath standard. See Section 12.11, “XML Functions”.
MySQL supports a native JSON data type as defined by RFC 7159, and based on the ECMAScript standard (ECMA-262). See Section 11.6, “The JSON Data Type”. MySQL also implements a subset of the SQL/JSON functions specified by a pre-publication draft of the SQL:2016 standard; see Section 12.17, “JSON Functions”, for more information.
The MySQL server can operate in different SQL modes, and can apply
these modes differently for different clients, depending on the
value of the sql_mode system
variable. DBAs can set the global SQL mode to match site server
operating requirements, and each application can set its session
SQL mode to its own requirements.
Modes affect the SQL syntax MySQL supports and the data validation checks it performs. This makes it easier to use MySQL in different environments and to use MySQL together with other database servers.
For more information on setting the SQL mode, see Section 5.1.11, “Server SQL Modes”.
To run MySQL Server in ANSI mode, start mysqld
with the --ansi option. Running the
server in ANSI mode is the same as starting it with the following
options:
--transaction-isolation=SERIALIZABLE --sql-mode=ANSI
To achieve the same effect at runtime, execute these two statements:
SET GLOBAL TRANSACTION ISOLATION LEVEL SERIALIZABLE; SET GLOBAL sql_mode = 'ANSI';
You can see that setting the
sql_mode system variable to
'ANSI' enables all SQL mode options that are
relevant for ANSI mode as follows:
mysql>SET GLOBAL sql_mode='ANSI';mysql>SELECT @@GLOBAL.sql_mode;-> 'REAL_AS_FLOAT,PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,ANSI'
Running the server in ANSI mode with
--ansi is not quite the same as
setting the SQL mode to 'ANSI' because the
--ansi option also sets the
transaction isolation level.
See Section 5.1.7, “Server Command Options”.
MySQL Server supports some extensions that you probably will not find in other SQL DBMSs. Be warned that if you use them, your code will not be portable to other SQL servers. In some cases, you can write code that includes MySQL extensions, but is still portable, by using comments of the following form:
/*! MySQL-specific code */
In this case, MySQL Server parses and executes the code within
the comment as it would any other SQL statement, but other SQL
servers will ignore the extensions. For example, MySQL Server
recognizes the STRAIGHT_JOIN keyword in the
following statement, but other servers will not:
SELECT /*! STRAIGHT_JOIN */ col1 FROM table1,table2 WHERE ...
If you add a version number after the !
character, the syntax within the comment is executed only if the
MySQL version is greater than or equal to the specified version
number. The KEY_BLOCK_SIZE clause in the
following comment is executed only by servers from MySQL 5.1.10
or higher:
CREATE TABLE t1(a INT, KEY (a)) /*!50110 KEY_BLOCK_SIZE=1024 */;
The following descriptions list MySQL extensions, organized by category.
Organization of data on disk
MySQL Server maps each database to a directory under the MySQL data directory, and maps tables within a database to file names in the database directory. Consequently, database and table names are case-sensitive in MySQL Server on operating systems that have case-sensitive file names (such as most Unix systems). See Section 9.2.2, “Identifier Case Sensitivity”.
General language syntax
By default, strings can be enclosed by
" as well as '. If
the ANSI_QUOTES SQL
mode is enabled, strings can be enclosed only by
' and the server interprets strings
enclosed by " as identifiers.
\ is the escape character in strings.
In SQL statements, you can access tables from different
databases with the
db_name.tbl_name syntax. Some
SQL servers provide the same functionality but call this
User space. MySQL Server doesn't
support tablespaces such as used in statements like
this: CREATE TABLE ralph.my_table ... IN
my_tablespace.
SQL statement syntax
The ANALYZE TABLE,
CHECK TABLE,
OPTIMIZE TABLE, and
REPAIR TABLE statements.
The CREATE DATABASE,
DROP DATABASE, and
ALTER DATABASE
statements. See Section 13.1.12, “CREATE DATABASE Syntax”,
Section 13.1.24, “DROP DATABASE Syntax”, and
Section 13.1.2, “ALTER DATABASE Syntax”.
The DO statement.
EXPLAIN
SELECT to obtain a description of how tables
are processed by the query optimizer.
The
SET
statement. See Section 13.7.5.1, “SET Syntax for Variable Assignment”.
The SHOW statement. See
Section 13.7.6, “SHOW Syntax”. The information produced by many
of the MySQL-specific
SHOW statements can be
obtained in more standard fashion by using
SELECT to query
INFORMATION_SCHEMA. See
Chapter 25, INFORMATION_SCHEMA Tables.
Use of LOAD DATA. In many
cases, this syntax is compatible with Oracle
LOAD DATA. See
Section 13.2.7, “LOAD DATA Syntax”.
Use of RENAME TABLE. See
Section 13.1.36, “RENAME TABLE Syntax”.
Use of REPLACE instead of
DELETE plus
INSERT. See
Section 13.2.9, “REPLACE Syntax”.
Use of CHANGE
,
col_nameDROP
, or
col_nameDROP INDEX,
IGNORE or RENAME
in ALTER TABLE
statements. Use of multiple ADD,
ALTER, DROP, or
CHANGE clauses in an
ALTER TABLE statement.
See Section 13.1.9, “ALTER TABLE Syntax”.
Use of index names, indexes on a prefix of a column, and
use of INDEX or
KEY in CREATE
TABLE statements. See
Section 13.1.20, “CREATE TABLE Syntax”.
Use of TEMPORARY or IF NOT
EXISTS with CREATE
TABLE.
Use of IF EXISTS with
DROP TABLE and
DROP DATABASE.
The capability of dropping multiple tables with a single
DROP TABLE statement.
The ORDER BY and
LIMIT clauses of the
UPDATE and
DELETE statements.
INSERT INTO
syntax.
tbl_name
SET col_name = ...
The LOW_PRIORITY clause of the
INSERT,
REPLACE,
DELETE, and
UPDATE statements.
Use of INTO OUTFILE or INTO
DUMPFILE in
SELECT statements. See
Section 13.2.10, “SELECT Syntax”.
Options such as STRAIGHT_JOIN or
SQL_SMALL_RESULT in
SELECT statements.
You don't need to name all selected columns in the
GROUP BY clause. This gives better
performance for some very specific, but quite normal
queries. See
Section 12.20, “Aggregate (GROUP BY) Functions”.
You can specify ASC and
DESC with GROUP
BY, not just with ORDER BY.
The ability to set variables in a statement with the
:= assignment operator. See
Section 9.4, “User-Defined Variables”.
Data types
Functions and operators
To make it easier for users who migrate from other SQL environments, MySQL Server supports aliases for many functions. For example, all string functions support both standard SQL syntax and ODBC syntax.
MySQL Server understands the
|| and
&&
operators to mean logical OR and AND, as in the C
programming language. In MySQL Server,
|| and
OR are
synonyms, as are
&&
and AND.
Because of this nice syntax, MySQL Server doesn't
support the standard SQL
|| operator
for string concatenation; use
CONCAT() instead. Because
CONCAT() takes any number
of arguments, it is easy to convert use of the
|| operator
to MySQL Server.
Use of COUNT(DISTINCT
where
value_list)value_list has more than one
element.
String comparisons are case insensitive by default, with
sort ordering determined by the collation of the current
character set, which is utf8mb4 by
default. To perform case-sensitive comparisons instead,
you should declare your columns with the
BINARY attribute or use the
BINARY cast, which causes comparisons
to be done using the underlying character code values
rather than a lexical ordering.
The %
operator is a synonym for
MOD(). That is,
N %
MMOD(.
N,M)% is
supported for C programmers and for compatibility with
PostgreSQL.
The =,
<>,
<=,
<,
>=,
>,
<<,
>>,
<=>,
AND,
OR, or
LIKE
operators may be used in expressions in the output
column list (to the left of the FROM)
in SELECT statements. For
example:
mysql> SELECT col1=1 AND col2=2 FROM my_table;
The LAST_INSERT_ID()
function returns the most recent
AUTO_INCREMENT value. See
Section 12.15, “Information Functions”.
LIKE is permitted on
numeric values.
The REGEXP and
NOT REGEXP extended regular
expression operators.
CONCAT() or
CHAR() with one argument
or more than two arguments. (In MySQL Server, these
functions can take a variable number of arguments.)
The BIT_COUNT(),
CASE,
ELT(),
FROM_DAYS(),
FORMAT(),
IF(),
MD5(),
PERIOD_ADD(),
PERIOD_DIFF(),
TO_DAYS(), and
WEEKDAY() functions.
Use of TRIM() to trim
substrings. Standard SQL supports removal of single
characters only.
The GROUP BY functions
STD(),
BIT_OR(),
BIT_AND(),
BIT_XOR(), and
GROUP_CONCAT(). See
Section 12.20, “Aggregate (GROUP BY) Functions”.
We try to make MySQL Server follow the ANSI SQL standard and the ODBC SQL standard, but MySQL Server performs operations differently in some cases:
There are several differences between the MySQL and standard
SQL privilege systems. For example, in MySQL, privileges for
a table are not automatically revoked when you delete a
table. You must explicitly issue a
REVOKE statement to revoke
privileges for a table. For more information, see
Section 13.7.1.8, “REVOKE Syntax”.
The CAST() function does not
support cast to REAL or
BIGINT. See
Section 12.10, “Cast Functions and Operators”.
MySQL Server doesn't support the SELECT ... INTO
TABLE Sybase SQL extension. Instead, MySQL Server
supports the
INSERT INTO ...
SELECT standard SQL syntax, which is basically the
same thing. See Section 13.2.6.1, “INSERT ... SELECT Syntax”. For example:
INSERT INTO tbl_temp2 (fld_id)
SELECT tbl_temp1.fld_order_id
FROM tbl_temp1 WHERE tbl_temp1.fld_order_id > 100;
Alternatively, you can use
SELECT ... INTO
OUTFILE or
CREATE TABLE ...
SELECT.
You can use SELECT ...
INTO with user-defined variables. The same syntax
can also be used inside stored routines using cursors and
local variables. See Section 13.2.10.1, “SELECT ... INTO Syntax”.
If you access a column from the table to be updated in an
expression, UPDATE uses the
current value of the column. The second assignment in the
following statement sets col2 to the
current (updated) col1 value, not the
original col1 value. The result is that
col1 and col2 have the
same value. This behavior differs from standard SQL.
UPDATE t1 SET col1 = col1 + 1, col2 = col1;
The MySQL implementation of foreign keys differs from the SQL standard in the following key respects:
If there are several rows in the parent table that have
the same referenced key value,
InnoDB acts in foreign key
checks as if the other parent rows with the same key value
do not exist. For example, if you have defined a
RESTRICT type constraint, and there is
a child row with several parent rows,
InnoDB does not permit the deletion of
any of those parent rows.
InnoDB performs cascading operations
through a depth-first algorithm, based on records in the
indexes corresponding to the foreign key constraints.
A FOREIGN KEY constraint that
references a non-UNIQUE key is not
standard SQL but rather an
InnoDB extension.
If ON UPDATE CASCADE or ON
UPDATE SET NULL recurses to update the
same table it has previously updated
during the same cascade, it acts like
RESTRICT. This means that you cannot
use self-referential ON UPDATE CASCADE
or ON UPDATE SET NULL operations. This
is to prevent infinite loops resulting from cascaded
updates. A self-referential ON DELETE SET
NULL, on the other hand, is possible, as is a
self-referential ON DELETE CASCADE.
Cascading operations may not be nested more than 15 levels
deep.
In an SQL statement that inserts, deletes, or updates many
rows, foreign key constraints (like unique constraints)
are checked row-by-row. When performing foreign key
checks, InnoDB sets shared
row-level locks on child or parent records that it must
examine. MySQL checks foreign key constraints immediately;
the check is not deferred to transaction commit. According
to the SQL standard, the default behavior should be
deferred checking. That is, constraints are only checked
after the entire SQL statement has
been processed. This means that it is not possible to
delete a row that refers to itself using a foreign key.
For information about how the
InnoDB storage engine handles
foreign keys, see
Section 15.6.1.5, “InnoDB and FOREIGN KEY Constraints”.
Standard SQL uses the C syntax /* this is a comment
*/ for comments, and MySQL Server supports this
syntax as well. MySQL also support extensions to this syntax
that enable MySQL-specific SQL to be embedded in the comment,
as described in Section 9.6, “Comment Syntax”.
Standard SQL uses “--” as a
start-comment sequence. MySQL Server uses #
as the start comment character. MySQL Server also supports a
variant of the -- comment style. That is,
the -- start-comment sequence must be
followed by a space (or by a control character such as a
newline). The space is required to prevent problems with
automatically generated SQL queries that use constructs such
as the following, where we automatically insert the value of
the payment for payment:
UPDATE account SET credit=credit-payment
Consider about what happens if payment has
a negative value such as -1:
UPDATE account SET credit=credit--1
credit--1 is a valid expression in SQL, but
-- is interpreted as the start of a
comment, part of the expression is discarded. The result is a
statement that has a completely different meaning than
intended:
UPDATE account SET credit=credit
The statement produces no change in value at all. This
illustrates that permitting comments to start with
-- can have serious consequences.
Using our implementation requires a space following the
-- for it to be recognized as a
start-comment sequence in MySQL Server. Therefore,
credit--1 is safe to use.
Another safe feature is that the mysql
command-line client ignores lines that start with
--.
MySQL enables you to work both with transactional tables that permit rollback and with nontransactional tables that do not. Because of this, constraint handling is a bit different in MySQL than in other DBMSs. We must handle the case when you have inserted or updated a lot of rows in a nontransactional table for which changes cannot be rolled back when an error occurs.
The basic philosophy is that MySQL Server tries to produce an error for anything that it can detect while parsing a statement to be executed, and tries to recover from any errors that occur while executing the statement. We do this in most cases, but not yet for all.
The options MySQL has when an error occurs are to stop the statement in the middle or to recover as well as possible from the problem and continue. By default, the server follows the latter course. This means, for example, that the server may coerce invalid values to the closest valid values.
Several SQL mode options are available to provide greater control over handling of bad data values and whether to continue statement execution or abort when errors occur. Using these options, you can configure MySQL Server to act in a more traditional fashion that is like other DBMSs that reject improper input. The SQL mode can be set globally at server startup to affect all clients. Individual clients can set the SQL mode at runtime, which enables each client to select the behavior most appropriate for its requirements. See Section 5.1.11, “Server SQL Modes”.
The following sections describe how MySQL Server handles different types of constraints.
Normally, errors occur for data-change statements (such as
INSERT or
UPDATE) that would violate
primary-key, unique-key, or foreign-key constraints. If you
are using a transactional storage engine such as
InnoDB, MySQL automatically rolls back the
statement. If you are using a nontransactional storage engine,
MySQL stops processing the statement at the row for which the
error occurred and leaves any remaining rows unprocessed.
MySQL supports an IGNORE keyword for
INSERT,
UPDATE, and so forth. If you
use it, MySQL ignores primary-key or unique-key violations and
continues processing with the next row. See the section for
the statement that you are using (Section 13.2.6, “INSERT Syntax”,
Section 13.2.12, “UPDATE Syntax”, and so forth).
You can get information about the number of rows actually
inserted or updated with the
mysql_info() C API function.
You can also use the SHOW
WARNINGS statement. See
Section 28.7.7.36, “mysql_info()”, and
Section 13.7.6.40, “SHOW WARNINGS Syntax”.
InnoDB and NDB tables
support foreign keys. See
Section 1.8.3.2, “FOREIGN KEY Constraints”.
Foreign keys let you cross-reference related data across tables, and foreign key constraints help keep this spread-out data consistent.
MySQL supports ON UPDATE and ON
DELETE foreign key references in
CREATE TABLE and
ALTER TABLE statements. The
available referential actions are RESTRICT
(the default), CASCADE, SET
NULL, and NO ACTION.
SET DEFAULT is also supported by the MySQL
Server but is currently rejected as invalid by
InnoDB. Since MySQL does not
support deferred constraint checking, NO
ACTION is treated as RESTRICT.
For the exact syntax supported by MySQL for foreign keys, see
Section 13.1.20.6, “Using FOREIGN KEY Constraints”.
MATCH FULL, MATCH
PARTIAL, and MATCH SIMPLE are
allowed, but their use should be avoided, as they cause the
MySQL Server to ignore any ON DELETE or
ON UPDATE clause used in the same
statement. MATCH options do not have any
other effect in MySQL, which in effect enforces MATCH
SIMPLE semantics full-time.
MySQL requires that foreign key columns be indexed; if you create a table with a foreign key constraint but no index on a given column, an index is created.
You can obtain information about foreign keys from the
INFORMATION_SCHEMA.KEY_COLUMN_USAGE
table. An example of a query against this table is shown here:
mysql>SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, CONSTRAINT_NAME>FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE>WHERE REFERENCED_TABLE_SCHEMA IS NOT NULL;+--------------+---------------+-------------+-----------------+ | TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | CONSTRAINT_NAME | +--------------+---------------+-------------+-----------------+ | fk1 | myuser | myuser_id | f | | fk1 | product_order | customer_id | f2 | | fk1 | product_order | product_id | f1 | +--------------+---------------+-------------+-----------------+ 3 rows in set (0.01 sec)
Information about foreign keys on InnoDB
tables can also be found in the
INNODB_FOREIGN and
INNODB_FOREIGN_COLS tables, in
the INFORMATION_SCHEMA database.
InnoDB and NDB tables
support foreign keys. See
Section 15.6.1.5, “InnoDB and FOREIGN KEY Constraints”, for
information specific to foreign key support in
InnoDB.
By default, MySQL is forgiving of invalid or improper data values and coerces them to valid values for data entry. However, you can enable strict SQL mode to select more traditional treatment of bad values such that the server rejects them and aborts the statement in which they occur. See Section 5.1.11, “Server SQL Modes”.
This section describes the default (forgiving) behavior of MySQL, as well as the strict SQL mode and how it differs.
If you are not using strict mode, then whenever you insert an
“incorrect” value into a column, such as a
NULL into a NOT NULL
column or a too-large numeric value into a numeric column,
MySQL sets the column to the “best possible
value” instead of producing an error: The following
rules describe in more detail how this works:
If you try to store an out of range value into a numeric column, MySQL Server instead stores zero, the smallest possible value, or the largest possible value, whichever is closest to the invalid value.
For strings, MySQL stores either the empty string or as much of the string as can be stored in the column.
If you try to store a string that does not start with a number into a numeric column, MySQL Server stores 0.
Invalid values for ENUM and
SET columns are handled as
described in Section 1.8.3.4, “ENUM and SET Constraints”.
MySQL permits you to store certain incorrect date values
into DATE and
DATETIME columns (such as
'2000-02-31' or
'2000-02-00'). In this case, when an
application has not enabled strict SQL mode, it up to the
application to validate the dates before storing them. If
MySQL can store a date value and retrieve exactly the same
value, MySQL stores it as given. If the date is totally
wrong (outside the server's ability to store it), the
special “zero” date value
'0000-00-00' is stored in the column
instead.
If you try to store NULL into a column
that doesn't take NULL values, an error
occurs for single-row
INSERT statements. For
multiple-row INSERT
statements or for
INSERT INTO
... SELECT statements, MySQL Server stores the
implicit default value for the column data type. In
general, this is 0 for numeric types,
the empty string ('') for string types,
and the “zero” value for date and time types.
Implicit default values are discussed in
Section 11.7, “Data Type Default Values”.
If an INSERT statement
specifies no value for a column, MySQL inserts its default
value if the column definition includes an explicit
DEFAULT clause. If the definition has
no such DEFAULT clause, MySQL inserts
the implicit default value for the column data type.
The reason for using the preceding rules in nonstrict mode is that we can't check these conditions until the statement has begun executing. We can't just roll back if we encounter a problem after updating a few rows, because the storage engine may not support rollback. The option of terminating the statement is not that good; in this case, the update would be “half done,” which is probably the worst possible scenario. In this case, it is better to “do the best you can” and then continue as if nothing happened.
You can select stricter treatment of input values by using the
STRICT_TRANS_TABLES or
STRICT_ALL_TABLES SQL modes:
SET sql_mode = 'STRICT_TRANS_TABLES'; SET sql_mode = 'STRICT_ALL_TABLES';
STRICT_TRANS_TABLES enables
strict mode for transactional storage engines, and also to
some extent for nontransactional engines. It works like this:
For transactional storage engines, bad data values occurring anywhere in a statement cause the statement to abort and roll back.
For nontransactional storage engines, a statement aborts
if the error occurs in the first row to be inserted or
updated. (When the error occurs in the first row, the
statement can be aborted to leave the table unchanged,
just as for a transactional table.) Errors in rows after
the first do not abort the statement, because the table
has already been changed by the first row. Instead, bad
data values are adjusted and result in warnings rather
than errors. In other words, with
STRICT_TRANS_TABLES, a
wrong value causes MySQL to roll back all updates done so
far, if that can be done without changing the table. But
once the table has been changed, further errors result in
adjustments and warnings.
For even stricter checking, enable
STRICT_ALL_TABLES. This is
the same as
STRICT_TRANS_TABLES except
that for nontransactional storage engines, errors abort the
statement even for bad data in rows following the first row.
This means that if an error occurs partway through a
multiple-row insert or update for a nontransactional table, a
partial update results. Earlier rows are inserted or updated,
but those from the point of the error on are not. To avoid
this for nontransactional tables, either use single-row
statements or else use
STRICT_TRANS_TABLES if
conversion warnings rather than errors are acceptable. To
avoid problems in the first place, do not use MySQL to check
column content. It is safest (and often faster) to let the
application ensure that it passes only valid values to the
database.
With either of the strict mode options, you can cause errors
to be treated as warnings by using
INSERT
IGNORE or UPDATE IGNORE rather
than INSERT or
UPDATE without
IGNORE.
ENUM and
SET columns provide an
efficient way to define columns that can contain only a given
set of values. See Section 11.4.4, “The ENUM Type”, and
Section 11.4.5, “The SET Type”.
With strict mode enabled (see Section 5.1.11, “Server SQL Modes”), the
definition of a ENUM or
SET column acts as a constraint
on values entered into the column. An error occurs for values
that do not satisfy these conditions:
An ENUM value must be one
of those listed in the column definition, or the internal
numeric equivalent thereof. The value cannot be the error
value (that is, 0 or the empty string). For a column
defined as
ENUM('a','b','c'), values
such as '', 'd', or
'ax' are invalid and are rejected.
A SET value must be the
empty string or a value consisting only of the values
listed in the column definition separated by commas. For a
column defined as
SET('a','b','c'), values
such as 'd' or
'a,b,c,d' are invalid and are rejected.
Errors for invalid values can be suppressed in strict mode if
you use INSERT
IGNORE or UPDATE IGNORE. In this
case, a warning is generated rather than an error. For
ENUM, the value is inserted as
the error member (0). For
SET, the value is inserted as
given except that any invalid substrings are deleted. For
example, 'a,x,b,y' results in a value of
'a,b'.
The following sections list developers, contributors, and supporters that have helped to make MySQL what it is today.
Although Oracle Corporation and/or its affiliates own all
copyrights in the MySQL server and the
MySQL manual, we wish to recognize those who
have made contributions of one kind or another to the
MySQL distribution. Contributors are listed
here, in somewhat random order:
Gianmassimo Vigazzola <[email protected]> or
<[email protected]>
The initial port to Win32/NT.
Per Eric Olsson
For constructive criticism and real testing of the dynamic record format.
Irena Pancirov <[email protected]>
Win32 port with Borland compiler.
mysqlshutdown.exe and
mysqlwatch.exe.
David J. Hughes
For the effort to make a shareware SQL database. At TcX, the
predecessor of MySQL AB, we started with
mSQL, but found that it couldn't satisfy
our purposes so instead we wrote an SQL interface to our
application builder Unireg. mysqladmin and
mysql client are programs that were largely
influenced by their mSQL counterparts. We
have put a lot of effort into making the MySQL syntax a
superset of mSQL. Many of the API's ideas
are borrowed from mSQL to make it easy to
port free mSQL programs to the MySQL API.
The MySQL software doesn't contain any code from
mSQL. Two files in the distribution
(client/insert_test.c and
client/select_test.c) are based on the
corresponding (noncopyrighted) files in the
mSQL distribution, but are modified as
examples showing the changes necessary to convert code from
mSQL to MySQL Server.
(mSQL is copyrighted David J. Hughes.)
Patrick Lynch
For helping us acquire http://www.mysql.com/.
Fred Lindberg
For setting up qmail to handle the MySQL mailing list and for the incredible help we got in managing the MySQL mailing lists.
Igor Romanenko <[email protected]>
mysqldump (previously
msqldump, but ported and enhanced by
Monty).
Yuri Dario
For keeping up and extending the MySQL OS/2 port.
Tim Bunce
Author of mysqlhotcopy.
Zarko Mocnik <[email protected]>
Sorting for Slovenian language.
"TAMITO" <[email protected]>
The _MB character set macros and the ujis
and sjis character sets.
Joshua Chamas <[email protected]>
Base for concurrent insert, extended date syntax, debugging on NT, and answering on the MySQL mailing list.
Yves Carlier <[email protected]>
mysqlaccess, a program to show the access rights for a user.
Rhys Jones <[email protected]> (And GWE Technologies
Limited)
For one of the early JDBC drivers.
Dr Xiaokun Kelvin ZHU <[email protected]>
Further development of one of the early JDBC drivers and other MySQL-related Java tools.
James Cooper <[email protected]>
For setting up a searchable mailing list archive at his site.
Rick Mehalick <[email protected]>
For xmysql, a graphical X client for MySQL
Server.
Doug Sisk <[email protected]>
For providing RPM packages of MySQL for Red Hat Linux.
Diemand Alexander V. <[email protected]>
For providing RPM packages of MySQL for Red Hat Linux-Alpha.
Antoni Pamies Olive <[email protected]>
For providing RPM versions of a lot of MySQL clients for Intel and SPARC.
Jay Bloodworth <[email protected]>
For providing RPM versions for MySQL 3.21.
David Sacerdote <[email protected]>
Ideas for secure checking of DNS host names.
Wei-Jou Chen <[email protected]>
Some support for Chinese(BIG5) characters.
Wei He <[email protected]>
A lot of functionality for the Chinese(GBK) character set.
Jan Pazdziora <[email protected]>
Czech sorting order.
Zeev Suraski <[email protected]>
FROM_UNIXTIME() time
formatting, ENCRYPT()
functions, and bison advisor. Active
mailing list member.
Luuk de Boer <[email protected]>
Ported (and extended) the benchmark suite to
DBI/DBD. Have been of
great help with crash-me and running
benchmarks. Some new date functions. The
mysql_setpermission script.
Alexis Mikhailov <[email protected]>
User-defined functions (UDFs); CREATE
FUNCTION and DROP
FUNCTION.
Andreas F. Bobak <[email protected]>
The AGGREGATE extension to user-defined
functions.
Ross Wakelin <[email protected]>
Help to set up InstallShield for MySQL-Win32.
Jethro Wright III <[email protected]>
The libmysql.dll library.
James Pereria <[email protected]>
Mysqlmanager, a Win32 GUI tool for administering MySQL Servers.
Curt Sampson <[email protected]>
Porting of MIT-pthreads to NetBSD/Alpha and NetBSD 1.3/i386.
Martin Ramsch <[email protected]>
Examples in the MySQL Tutorial.
Steve Harvey
For making mysqlaccess more secure.
Konark IA-64 Centre of Persistent Systems Private Limited
Help with the Win64 port of the MySQL server.
Albert Chin-A-Young.
Configure updates for Tru64, large file support and better TCP wrappers support.
John Birrell
Emulation of pthread_mutex() for OS/2.
Benjamin Pflugmann
Extended MERGE tables to handle
INSERTS. Active member on the MySQL mailing
lists.
Jocelyn Fournier
Excellent spotting and reporting innumerable bugs (especially in the MySQL 4.1 subquery code).
Marc Liyanage
Maintaining the OS X packages and providing invaluable feedback on how to create OS X packages.
Robert Rutherford
Providing invaluable information and feedback about the QNX port.
Previous developers of NDB Cluster
Lots of people were involved in various ways summer students, master thesis students, employees. In total more than 100 people so too many to mention here. Notable name is Ataullah Dabaghi who up until 1999 contributed around a third of the code base. A special thanks also to developers of the AXE system which provided much of the architectural foundations for NDB Cluster with blocks, signals and crash tracing functionality. Also credit should be given to those who believed in the ideas enough to allocate of their budgets for its development from 1992 to present time.
Google Inc.
We wish to recognize Google Inc. for contributions to the MySQL distribution: Mark Callaghan's SMP Performance patches and other patches.
Other contributors, bugfinders, and testers: James H. Thompson,
Maurizio Menghini, Wojciech Tryc, Luca Berra, Zarko Mocnik, Wim
Bonis, Elmar Haneke, <jehamby@lightside>,
<[email protected]>,
<[email protected]>, Ted Deppner
<[email protected]>, Mike Simons, Jaakko Hyvatti.
And lots of bug report/patches from the folks on the mailing list.
A big tribute goes to those that help us answer questions on the MySQL mailing lists:
Daniel Koch <[email protected]>
Irix setup.
Luuk de Boer <[email protected]>
Benchmark questions.
Tim Sailer <[email protected]>
DBD::mysql questions.
Boyd Lynn Gerber <[email protected]>
SCO-related questions.
Richard Mehalick <[email protected]>
xmysql-related questions and basic
installation questions.
Zeev Suraski <[email protected]>
Apache module configuration questions (log & auth), PHP-related questions, SQL syntax-related questions and other general questions.
Francesc Guasch <[email protected]>
General questions.
Jonathan J Smith <[email protected]>
Questions pertaining to OS-specifics with Linux, SQL syntax, and other things that might need some work.
David Sklar <[email protected]>
Using MySQL from PHP and Perl.
Alistair MacDonald <[email protected]>
Is flexible and can handle Linux and perhaps HP-UX.
John Lyon <[email protected]>
Questions about installing MySQL on Linux systems, using
either .rpm files or compiling from
source.
Lorvid Ltd. <[email protected]>
Simple billing/license/support/copyright issues.
Patrick Sherrill <[email protected]>
ODBC and VisualC++ interface questions.
Randy Harmon <[email protected]>
DBD, Linux, some SQL syntax questions.
The following people have helped us with writing the MySQL documentation and translating the documentation or error messages in MySQL.
Paul DuBois
Ongoing help with making this manual correct and understandable. That includes rewriting Monty's and David's attempts at English into English as other people know it.
Kim Aldale
Helped to rewrite Monty's and David's early attempts at English into English.
Michael J. Miller Jr.
<[email protected]>
For the first MySQL manual. And a lot of spelling/language fixes for the FAQ (that turned into the MySQL manual a long time ago).
Yan Cailin
First translator of the MySQL Reference Manual into simplified Chinese in early 2000 on which the Big5 and HK coded versions were based.
Jay Flaherty <[email protected]>
Big parts of the Perl
DBI/DBD section in the
manual.
Paul Southworth <[email protected]>, Ray Loyzaga
<[email protected]>
Proof-reading of the Reference Manual.
Therrien Gilbert <[email protected]>, Jean-Marc
Pouyot <[email protected]>
French error messages.
Petr Snajdr, <[email protected]>
Czech error messages.
Jaroslaw Lewandowski <[email protected]>
Polish error messages.
Miguel Angel Fernandez Roiz
Spanish error messages.
Roy-Magne Mo <[email protected]>
Norwegian error messages and testing of MySQL 3.21.xx.
Timur I. Bakeyev <[email protected]>
Russian error messages.
<[email protected]> & Filippo Grassilli
<[email protected]>
Italian error messages.
Dirk Munzinger <[email protected]>
German error messages.
Billik Stefan <[email protected]>
Slovak error messages.
Stefan Saroiu <[email protected]>
Romanian error messages.
Peter Feher
Hungarian error messages.
Roberto M. Serqueira
Portuguese error messages.
Carsten H. Pedersen
Danish error messages.
Arjen Lentz
Dutch error messages, completing earlier partial translation (also work on consistency and spelling).
The following is a list of creators/maintainers of some of the most important API/packages/applications that a lot of people use with MySQL.
We cannot list every possible package here because the list would then be way to hard to maintain. For other packages, please refer to the software portal at http://solutions.mysql.com/software/.
Tim Bunce, Alligator Descartes
For the DBD (Perl) interface.
Andreas Koenig <[email protected]>
For the Perl interface for MySQL Server.
Jochen Wiedmann <[email protected]>
For maintaining the Perl DBD::mysql module.
Eugene Chan <[email protected]>
For porting PHP for MySQL Server.
Georg Richter
MySQL 4.1 testing and bug hunting. New PHP 5.0
mysqli extension (API) for use with MySQL
4.1 and up.
Giovanni Maruzzelli <[email protected]>
For porting iODBC (Unix ODBC).
Xavier Leroy <[email protected]>
The author of LinuxThreads (used by the MySQL Server on Linux).
The following is a list of some of the tools we have used to create MySQL. We use this to express our thanks to those that has created them as without these we could not have made MySQL what it is today.
Free Software Foundation
From whom we got an excellent compiler
(gcc), an excellent debugger
(gdb and the libc
library (from which we have borrowed
strto.c to get some code working in
Linux).
Free Software Foundation & The XEmacs development team
For a really great editor/environment.
Julian Seward
Author of valgrind, an excellent memory
checker tool that has helped us find a lot of otherwise hard
to find bugs in MySQL.
Dorothea Lütkehaus and Andreas Zeller
For DDD (The Data Display Debugger) which
is an excellent graphical front end to
gdb).
Although Oracle Corporation and/or its affiliates own all
copyrights in the MySQL server and the
MySQL manual, we wish to recognize the
following companies, which helped us finance the development of
the MySQL server, such as by paying us for
developing a new feature or giving us hardware for development of
the MySQL server.
VA Linux / Andover.net
Funded replication.
NuSphere
Editing of the MySQL manual.
Stork Design studio
The MySQL website in use between 1998-2000.
Intel
Contributed to development on Windows and Linux platforms.
Compaq
Contributed to Development on Linux/Alpha.
SWSoft
Development on the embedded mysqld version.
FutureQuest
The --skip-show-database
option.