13.7.11.3. How to Downgrade

13.7.11.3.1. Converting Tables

The built-in InnoDB in MySQL can access only tables in the “Antelope” file format, that is, in the REDUNDANT or COMPACT row format. If you have created tables in COMPRESSED or DYNAMIC format, the corresponding tablespaces in the new “Barracuda” file format, and it is necessary to downgrade these tables.

First, identify the tables that require conversion, by executing this command:

SELECT table_schema, table_name, row_format
FROM information_schema.tables
WHERE engine='innodb'
AND row_format NOT IN ('Redundant', 'Compact');

Next, for each table that requires conversion, run the following command:

ALTER TABLE table_name ROW_FORMAT=COMPACT;

This command copies the table and its indexes to a new tablespace in the “Antelope” format. See Section 13.7.2, “Fast Index Creation in the InnoDB Storage Engine” for a discussion of exactly how such index creation operations are performed.

13.7.11.3.2. Adjusting the Configuration

Before you shut down the InnoDB storage engine and start the basic built-in InnoDB in MySQL, review the configuration files. Changes to the startup options do not take effect until the server is restarted, or the InnoDB storage engine is uninstalled and reinstalled.

InnoDB 1.1 includes several configuration parameters that are not recognized by the built-in InnoDB prior to MySQL 5.5. For example, MySQL 5.1 and earlier (without the InnoDB Plugin) does not recognize innodb_file_format, innodb_file_format_check, and innodb_strict_mode. See Section 13.7.14.1, “New Parameters” for a complete list of such configuration parameters that could cause downgrade issues. To include these parameters in the configuration file, use the loose_ form of the parameter names, so that the earlier version of InnoDB can start.

In MySQL, configuration options can be specified in the mysqld command line or the option file (my.cnf or my.ini). See Section 4.2.3.3, “Using Option Files” for more information.

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