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 5.0.13 to 5.0.12) 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:
Read the upgrading section for the release series from which
you are downgrading to be sure that it does not have any
features you really need. Section 2.10, “Upgrading MySQL”.
If there is a downgrading section for that version, you should
read that as well.
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 2.10.2, “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:
Stop the older MySQL server that you are downgrading to.
Restart the newer MySQL server you are downgrading from.
Dump any tables that were inaccessible to the older server by
using mysqldump to create a dump file.
Stop the newer MySQL server and restart the older one.
Reload the dump file into the older server. Your tables should
be accessible.
