MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0

16.2 The MyISAM Storage Engine

MyISAM is based on the older (and no longer available) ISAM storage engine but has many useful extensions.

Table 16.2 MyISAM Storage Engine Features

Feature Support
B-tree indexes Yes
Backup/point-in-time recovery (Implemented in the server, rather than in the storage engine.) Yes
Cluster database support No
Clustered indexes No
Compressed data Yes (Compressed MyISAM tables are supported only when using the compressed row format. Tables using the compressed row format with MyISAM are read only.)
Data caches No
Encrypted data Yes (Implemented in the server via encryption functions.)
Foreign key support No
Full-text search indexes Yes
Geospatial data type support Yes
Geospatial indexing support Yes
Hash indexes No
Index caches Yes
Locking granularity Table
MVCC No
Replication support (Implemented in the server, rather than in the storage engine.) Yes
Storage limits 256TB
T-tree indexes No
Transactions No
Update statistics for data dictionary Yes

Each MyISAM table is stored on disk in two files. The files have names that begin with the table name and have an extension to indicate the file type. The data file has an .MYD (MYData) extension. The index file has an .MYI (MYIndex) extension. The table definition is stored in the MySQL data dictionary.

To specify explicitly that you want a MyISAM table, indicate that with an ENGINE table option:

CREATE TABLE t (i INT) ENGINE = MYISAM;

In MySQL 8.0, it is normally necessary to use ENGINE to specify the MyISAM storage engine because InnoDB is the default engine.

You can check or repair MyISAM tables with the mysqlcheck client or myisamchk utility. You can also compress MyISAM tables with myisampack to take up much less space. See Section 4.5.3, “mysqlcheck — A Table Maintenance Program”, Section 4.6.4, “myisamchk — MyISAM Table-Maintenance Utility”, and Section 4.6.6, “myisampack — Generate Compressed, Read-Only MyISAM Tables”.

In MySQL 8.0, the MyISAM storage engine provides no partitioning support. Partitioned MyISAM tables created in previous versions of MySQL cannot be used in MySQL 8.0. For more information, see Section 23.6.2, “Partitioning Limitations Relating to Storage Engines”. For help with upgrading such tables so that they can be used in MySQL 8.0, see Section 2.11.4, “Changes in MySQL 8.0”.

MyISAM tables have the following characteristics:

MyISAM also supports the following features:

Additional Resources