Chapter 13. Storage Engines

Table of Contents

13.1. Comparing Transaction and Nontransaction Engines
13.2. Other Storage Engines
13.3. Setting the Storage Engine
13.4. Overview of MySQL Storage Engine Architecture
13.4.1. Pluggable Storage Engine Architecture
13.4.2. The Common Database Server Layer
13.5. The MyISAM Storage Engine
13.5.1. MyISAM Startup Options
13.5.2. Space Needed for Keys
13.5.3. MyISAM Table Storage Formats
13.5.4. MyISAM Table Problems
13.6. The InnoDB Storage Engine
13.6.1. InnoDB as the Default MySQL Storage Engine
13.6.2. Configuring InnoDB
13.6.3. Using Per-Table Tablespaces
13.6.4. InnoDB Startup Options and System Variables
13.6.5. Creating and Using InnoDB Tables
13.6.6. Adding, Removing, or Resizing InnoDB Data and Log Files
13.6.7. Backing Up and Recovering an InnoDB Database
13.6.8. Moving an InnoDB Database to Another Machine
13.6.9. The InnoDB Transaction Model and Locking
13.6.10. InnoDB Multi-Versioning
13.6.11. InnoDB Table and Index Structures
13.6.12. InnoDB Disk I/O and File Space Management
13.6.13. InnoDB Error Handling
13.6.14. InnoDB Performance Tuning and Troubleshooting
13.6.15. Limits on InnoDB Tables
13.7. New Features of InnoDB 1.1
13.7.1. Introduction to InnoDB 1.1
13.7.2. Fast Index Creation in the InnoDB Storage Engine
13.7.3. InnoDB Data Compression
13.7.4. InnoDB File Format Management
13.7.5. Storage of Variable-Length Columns
13.7.6. InnoDB INFORMATION_SCHEMA tables
13.7.7. Performance and Scalability Enhancements
13.7.8. Changes for Flexibility, Ease of Use and Reliability
13.7.9. Installing the InnoDB Storage Engine
13.7.10. Upgrading the InnoDB Storage Engine
13.7.11. Downgrading the InnoDB Storage Engine
13.7.12. InnoDB Storage Engine Change History
13.7.13. Third-Party Software
13.7.14. List of Parameters Changed in InnoDB 1.1 and InnoDB Plugin 1.0
13.8. The MERGE Storage Engine
13.8.1. MERGE Table Advantages and Disadvantages
13.8.2. MERGE Table Problems
13.9. The MEMORY Storage Engine
13.10. The EXAMPLE Storage Engine
13.11. The FEDERATED Storage Engine
13.11.1. FEDERATED Storage Engine Overview
13.11.2. How to Create FEDERATED Tables
13.11.3. FEDERATED Storage Engine Notes and Tips
13.11.4. FEDERATED Storage Engine Resources
13.12. The ARCHIVE Storage Engine
13.13. The CSV Storage Engine
13.13.1. Repairing and Checking CSV Tables
13.13.2. CSV Limitations
13.14. The BLACKHOLE Storage 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 enables storage engines to be loaded into and unloaded from a running MySQL server.

To determine which storage engines your server supports by using the SHOW ENGINES statement. The value in the Support column indicates whether an engine can be used. A value of YES, NO, or DEFAULT indicates that an engine is available, not available, or available and currently set as the default storage engine.

*************************** 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 Web site. 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 B.2, “MySQL 5.5 FAQ: Storage Engines”.

MySQL 5.5 supported storage engines

  • InnoDB: 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. InnoDB stores user data in clustered indexes to reduce I/O for common queries based on primary keys. To maintain data integrity, InnoDB also supports FOREIGN KEY referential-integrity constraints. InnoDB is the default storage engine as of MySQL 5.5.5.

  • MyISAM: The MySQL storage engine that is used the most in Web, data warehousing, and other application environments. MyISAM is supported in all MySQL configurations, and is the default storage engine prior to MySQL 5.5.5.

  • Memory: 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 HEAP engine.

  • Merge: Enables 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 data warehousing.

  • Archive: Provides the perfect solution for storing and retrieving large amounts of seldom-referenced historical, archived, or security audit information.

  • Federated: 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.

  • CSV: 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.

  • Blackhole: 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.

  • Example: 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

Storage limits256TBRAM64TBNone384EB
Locking granularityTableTableRowRowRow
Geospatial data type supportYesNoYesYesYes
Geospatial indexing supportYesNoNoNoNo
B-tree indexesYesYesYesNoYes
Hash indexesNoYesNoNoYes
Full-text search indexesYesNoNoNoNo
Clustered indexesNoNoYesNoNo
Data cachesNoN/AYesNoYes
Index cachesYesN/AYesNoYes
Compressed dataYes[a]NoYes[b]YesNo
Encrypted data[c]YesYesYesYesYes
Cluster database supportNoNoNoNoYes
Replication support[d]YesYesYesYesYes
Foreign key supportNoNoYesNoNo
Backup / point-in-time recovery[e]YesYesYesYesYes
Query cache supportYesYesYesYesYes
Update statistics for data dictionaryYesYesYesYesYes

[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 require the InnoDB Barracuda file format.

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

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

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

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