2.11. 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 4.1.13 to 4.1.12) 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, you can 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 2.10.3, "Copying MySQL Databases to Another Machine."
The normal symptom of a downward-incompatible table format change when you downgrade is that you can't open tables. In that case, use the following procedure:
2.11.1. Downgrading to MySQL 4.1
Incorrect information in file: './mysql/user.frm'
In this case, you can do the following:
If the preceding procedure fails, you should be able to do the following instead: