MySQL 5.1 and up supports a plugin API that allows the loading and unloading of server components at runtime, without restarting the server. The components supported by this operation include, but are not limited to, full-text parser plugins, storage-engines and server extensions. In MySQL 5.1, the storage engines can be included in the server as plugins.

Full-text parser plugins can be used to replace or augment the built-in full-text parser. For example, a plugin can parse text into words using rules that differ from those used by the built-in parser. This can be useful if you need to parse text with characteristics different from those expected by the built-in parser.

The plugin interface is intended as the successor to the older user-defined function (UDF) interface. The plugin interface eventually will include an API for creating UDFs, and it is intended this plugin UDF API will replace the older nonplugin UDF API. After that point, it will be possible for UDFs to be revised for use as plugin UDFs so that they can take advantage of the better security and versioning capabilities of the plugin API. Eventually, support for the older UDF API will be phased out.

The plugin interface requires the plugin table in the mysql database. This table is created as part of the MySQL installation process. If you are upgrading from a version older than MySQL 5.1, you should run the mysql_upgrade command to create this table. See Section 4.4.8, “mysql_upgrade — Check Tables for MySQL Upgrade”.

For more information on the Plugin API and how it can be used with storage engines, see MySQL Internals: Custom Engine.