2.13.2. Downgrading MySQL

This section describes what you should do to downgrade to an older MySQL version in the unlikely case that the previous version worked better than the new one.

If you are downgrading within the same release series (for example, from 5.1.13 to 5.1.12) the general rule is that you just have to install the new binaries on top of the old ones. There is no need to do anything with the databases. As always, however, it is always a good idea to make a backup.

The following items form a checklist of things you should do whenever you perform a downgrade:

In most cases, you can move the MySQL format files and data files between different versions on the same architecture as long as you stay within versions for the same release series of MySQL.

If you downgrade from one release series to another, there may be incompatibilities in table storage formats. In this case, use mysqldump to dump your tables before downgrading. After downgrading, reload the dump file using mysql or mysqlimport to re-create your tables. For examples, see Section 2.13.5, “Copying MySQL Databases to Another Machine”.

A typical symptom of a downward-incompatible table format change when you downgrade is that you cannot open tables. In that case, use the following procedure:

  1. Stop the older MySQL server that you are downgrading to.

  2. Restart the newer MySQL server you are downgrading from.

  3. Dump any tables that were inaccessible to the older server by using mysqldump to create a dump file.

  4. Stop the newer MySQL server and restart the older one.

  5. Reload the dump file into the older server. Your tables should be accessible.

It might also be the case that system tables in the mysql database have changed and that downgrading introduces some loss of functionality or requires some adjustments. Here are some examples:

  • Trigger creation requires the TRIGGER privilege as of MySQL 5.1. In MySQL 5.0, there is no TRIGGER privilege and SUPER is required instead. If you downgrade from MySQL 5.1 to 5.0, you will need to give the SUPER privilege to those accounts that had the TRIGGER privilege in 5.1.

  • Triggers were added in MySQL 5.0, so if you downgrade from 5.0 to 4.1, you cannot use triggers at all.

  • The mysql.proc.comment column definition changed between MySQL 5.1 and 5.5. After a downgrade from 5.5 to 5.1, this table is seen as corrupt and in need of repair. To workaround this problem, execute mysql_upgrade from the version of MySQL to which you downgraded.

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