The world's most popular open source database
Table of Contents [+/-]
MyISAMStorage Engine [+/-]
InnoDBStorage Engine [+/-]
InnoDBStartup Options and System Variables
InnoDBData and Log Files
InnoDBDatabase to Another Machine
InnoDBTransaction Model and Locking
InnoDBTable and Index Structures
InnoDBDisk I/O and File Space Management
InnoDBPerformance Tuning and Troubleshooting
IBMDB2IStorage Engine [+/-]
MERGEStorage Engine [+/-]
HEAP) Storage Engine
FEDERATEDStorage Engine [+/-]
CSVStorage Engine [+/-]
MySQL supports several storage engines that act as handlers for different table types. MySQL storage engines include both those that handle transaction-safe tables and those that handle nontransaction-safe tables.
MySQL Server uses a pluggable storage engine architecture that allows storage engines to be loaded into and unloaded from a running MySQL server.
Prior to MySQL 5.4.2, the pluggable storage engine architecture is supported on Unix platforms only and pluggable storage engines are not supported on Windows.
To determine which storage engines your server supports by using the
SHOW ENGINES statement. The value in
Support column indicates whether an engine
can be used. A value of
DEFAULT indicates that
an engine is available, not available, or avaiable and current set
as the default storage engine.
SHOW ENGINES\G*************************** 1. row *************************** Engine: FEDERATED Support: NO Comment: Federated MySQL storage engine Transactions: NULL XA: NULL Savepoints: NULL *************************** 2. row *************************** Engine: MRG_MYISAM Support: YES Comment: Collection of identical MyISAM tables Transactions: NO XA: NO Savepoints: NO *************************** 3. row *************************** Engine: MyISAM Support: DEFAULT Comment: Default engine as of MySQL 3.23 with great performance Transactions: NO XA: NO Savepoints: NO ...
This chapter describes each of the MySQL storage engines except for
NDBCLUSTER, which is covered in
MySQL Cluster NDB 6.X/7.X. It also contains a
description of the pluggable storage engine architecture (see
Section 13.4, “Overview of MySQL Storage Engine Architecture”).
For information about storage engine support offered in commercial MySQL Server binaries, see MySQL Enterprise Server 5.1, on the MySQL website. The storage engines available might depend on which edition of Enterprise Server you are using.
For answers to some commonly asked questions about MySQL storage engines, see Section A.2, “MySQL 5.4 FAQ — Storage Engines”.
MySQL 5.4 supported storage engines
— The default MySQL storage engine and the one that is
used the most in Web, data warehousing, and other application
MyISAM is supported in all
MySQL configurations, and is the default storage engine unless
you have configured MySQL to use a different one by default.
A transaction-safe (ACID compliant) storage engine for MySQL
that has commit, rollback, and crash-recovery capabilities to
protect user data.
InnoDB row-level locking
(without escalation to coarser granularity locks) and
Oracle-style consistent nonlocking reads increase multi-user
concurrency and performance.
user data in clustered indexes to reduce I/O for common queries
based on primary keys. To maintain data integrity,
InnoDB also supports
KEY referential-integrity constraints.
— Stores all data in RAM for extremely fast access in
environments that require quick lookups of reference and other
like data. This engine was formerly known as the
— Allows a MySQL DBA or developer to logically group a
series of identical
MyISAM tables and
reference them as one object. Good for VLDB environments such as
— Provides the perfect solution for storing and retrieving
large amounts of seldom-referenced historical, archived, or
security audit information.
— Offers the ability to link separate MySQL servers to
create one logical database from many physical servers. Very
good for distributed or data mart environments.
— The CSV storage engine stores data in text files using
comma-separated values format. You can use the CSV engine to
easily exchange data between other software and applications
that can import and export in CSV format.
— The Blackhole storage engine accepts but does not store
data and retrievals always return an empty set. The
functionality can be used in distributed database design where
data is automatically replicated, but not stored locally.
— The Example storage engine is “stub” engine
that does nothing. You can create tables with this engine, but
no data can be stored in them or retrieved from them. The
purpose of this engine is to serve as an example in the MySQL
source code that illustrates how to begin writing new storage
engines. As such, it is primarily of interest to developers.
It is important to remember that you are not restricted to using the same storage engine for an entire server or schema: you can use a different storage engine for each table in your schema.
Choosing a Storage Engine
The various storage engines provided with MySQL are designed with different use-cases in mind. To use the pluggable storage architecture effectively, it is good to have an idea of the advantages and disadvantages of the various storage engines. The following table provides an overview of some storage engines provided with MySQL:
Table 13.1. Storage Engines Feature Summary
|Geospatial datatype support||Yes||No||Yes||Yes||Yes|
|Geospatial indexing support||Yes||No||No||No||No|
|Full-text search indexes||Yes||No||No||No||No|
|Cluster database support||No||No||No||No||Yes|
|Foreign key support||No||No||Yes||No||No|
|Backup / point-in-time recovery[e]||Yes||Yes||Yes||Yes||Yes|
|Query cache support||Yes||Yes||Yes||Yes||Yes|
|Update statistics for data dictionary||Yes||Yes||Yes||Yes||Yes|
[a] Compressed MyISAM tables are supported only when using the compressed row format. Tables using the compressed row format with MyISAM are read only.
[b] Compressed InnoDB tables are supported only by InnoDB Plugin.
[c] Implemented in the server (via encryption functions), rather than in the storage engine.
[d] Implemented in the server, rather than in the storage engine
[e] Implemented in the server, rather than in the storage engine