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MySQL 5.0 Reference Manual :: 13 Storage Engines :: 13.7 The FEDERATED Storage Engine
13.7.1 Description of the FEDERATED Storage Engine »
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13.7. The FEDERATED Storage Engine

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13.7.1. Description of the FEDERATED Storage Engine
13.7.2. How to Use FEDERATED Tables
13.7.3. Limitations of the FEDERATED Storage Engine

The FEDERATED storage engine is available beginning with MySQL 5.0.3. It is a storage engine that accesses data in tables of remote databases rather than in local tables.

The FEDERATED storage engine is available beginning with MySQL 5.0.3. This storage engine enables data to be accessed from a remote MySQL database on a local server without using replication or cluster technology. When using a FEDERATED table, queries on the local server are automatically executed on the remote (federated) tables. No data is stored on the local tables.

To include the FEDERATED storage engine if you build MySQL from source, invoke configure with the --with-federated-storage-engine option.

Beginning with MySQL 5.0.64, the FEDERATED storage engine is not enabled by default in the running server; to enable FEDERATED, you must start the MySQL server binary using the --federated option.

To examine the source for the FEDERATED engine, look in the sql directory of a source distribution for MySQL 5.0.3 or newer.

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User Comments

Posted by Steven Hartland on March 18 2011 10:55pm[Delete] [Edit]

Optional storage engines require privileges and will fail to load when --skip-grant-tables is specified.

The result the entire db will fail to load and the following error will appear in the logs:
110318 21:37:23 [ERROR] /usr/local/libexec/mysqld: unknown option '--federated'

This in turn means that an upgrade from 5.x needs to be done in two steps if you have federated tables. Once with --skip-grant-tables and without --federated, the once without --skip-grant-tables and with --federated.

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