13.6. The InnoDB Storage Engine

InnoDB is a high-reliability and high-performance storage engine for MySQL. Starting with MySQL 5.5, it is the default MySQL storage engine. Key advantages of InnoDB include:

  • Its design follows the ACID model, with transactions featuring commit, rollback, and crash-recovery capabilities to protect user data.

  • Row-level locking and Oracle-style consistent reads increase multi-user concurrency and performance.

  • InnoDB tables arrange your data on disk to optimize common queries based on primary keys. Each InnoDB table has a primary key index called the clustered index that organizes the data to minimize I/O for primary key lookups.

  • To maintain data integrity, InnoDB also supports FOREIGN KEY referential-integrity constraints.

  • You can freely mix InnoDB tables with tables from other MySQL storage engines, even within the same statement. For example, you can use a join operation to combine data from InnoDB and MEMORY tables in a single query.

To determine whether your server supports InnoDB use the SHOW ENGINES statement. See Section 12.4.5.17, “SHOW ENGINES Syntax”.

Table 13.4. InnoDB Storage Engine Features

Storage limits64TBTransactionsYesLocking granularityRow
MVCCYesGeospatial data type supportYesGeospatial indexing supportNo
B-tree indexesYesHash indexesNoFull-text search indexesNo
Clustered indexesYesData cachesYesIndex cachesYes
Compressed dataYes[a]Encrypted data[b]YesCluster database supportNo
Replication support[c]YesForeign key supportYesBackup / point-in-time recovery[d]Yes
Query cache supportYesUpdate statistics for data dictionaryYes  

[a] Compressed InnoDB tables require the InnoDB Barracuda file format.

[b] Implemented in the server (via encryption functions), rather than in the storage engine.

[c] Implemented in the server, rather than in the storage product

[d] Implemented in the server, rather than in the storage product

InnoDB has been designed for maximum performance when processing large data volumes. Its CPU efficiency is probably not matched by any other disk-based relational database engine.

The InnoDB storage engine maintains its own buffer pool for caching data and indexes in main memory. InnoDB stores its tables and indexes in a tablespace, which may consist of several files (or raw disk partitions). This is different from, for example, MyISAM tables where each table is stored using separate files. InnoDB tables can be very large even on operating systems where file size is limited to 2GB.

The Windows Essentials installer makes InnoDB the MySQL default storage engine on Windows, if the server being installed supports InnoDB.

InnoDB is published under the same GNU GPL License Version 2 (of June 1991) as MySQL. For more information on MySQL licensing, see http://www.mysql.com/company/legal/licensing/.

Additional Resources

  • A forum dedicated to the InnoDB storage engine is available at http://forums.mysql.com/list.php?22.

  • The InnoDB storage engine in MySQL 5.5 releases includes a number performance improvements that in MySQL 5.1 were only available by installing the InnoDB Plugin. This latest InnoDB (now known as InnoDB 1.1) offers new features, improved performance and scalability, enhanced reliability and new capabilities for flexibility and ease of use. Among the top features are Fast Index Creation, table and index compression, file format management, new INFORMATION_SCHEMA tables, capacity tuning, multiple background I/O threads, multiple buffer pools, and group commit.

    For information about these features, see Section 13.7, “New Features of InnoDB 1.1”.

  • The MySQL Enterprise Backup product lets you back up a running MySQL database, including InnoDB and MyISAM tables, with minimal disruption to operations while producing a consistent snapshot of the database. When MySQL Enterprise Backup is copying InnoDB tables, reads and writes to both InnoDB and MyISAM tables can continue. During the copying of MyISAM and other non-InnoDB tables, reads (but not writes) to those tables are permitted. In addition, MySQL Enterprise Backup can create compressed backup files, and back up subsets of InnoDB tables. In conjunction with the MySQL binary log, you can perform point-in-time recovery. MySQL Enterprise Backup is included as part of the MySQL Enterprise subscription.

    For a more complete description of MySQL Enterprise Backup, see MySQL Enterprise Backup User's Guide (Version 3.5.2).

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