2.11.2 Downgrading MySQL

2.11.2.1 Downgrading to MySQL 5.1
2.11.2.2 Downgrading from MySQL Enterprise Edition to MySQL Community Server

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.

It is always a good idea to make a backup beforehand, in case a downgrade fails and leaves the instance in an unusable state.

To downgrade between General Availability (GA) status versions within the same release series, typically you just install the new binaries on top of the old ones and do not make any changes to the databases.

Downgrades between milestone releases (or from a GA release to a milestone release) within the same release series are not supported and you may encounter issues.

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 GA 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 2.11.5, “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: