Downgrade MySQL

• In the unlikely case that the previous version worked better than the new one, a downgrade may be necessary.
  • Back up the databases, including the mysql database that contains the grant tables.
    • It is always a good idea to make a backup.
  • If there is a downgrading section to the release notes, read it.

• In most cases, one can move the MySQL format files and data files between different versions on the same architecture within versions for the same release series of MySQL.
  • Downgrading from 5.1 to 5.0.

• If downgrading from one release series to another, there may be incompatibilities in table storage formats.
  • In this case, use mysqldump to dump the tables before downgrading.
  • After downgrading, reload the dump file using mysql or mysqlimport to re-create the tables.

• Being unable to open tables is the normal symptom of a downward-incompatible table format change.
  • In that case, to solve the problem, use the following procedure:
    • Stop the older MySQL server.
    • Restart the newer MySQL server.
    • 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.
    • The tables should be accessible.

What are the environment variables used by MySQL?

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© 2007 John Michael Pierobon

Notes