mysql_upgrade should be executed each time you upgrade MySQL. It checks all tables in all databases for incompatibilities with the current version of MySQL Server. If a table is found to have a possible incompatibility, it is checked. If any problems are found, the table is repaired. mysql_upgrade also upgrades the system tables so that you can take advantage of new privileges or capabilities that might have been added.
All checked and repaired tables are marked with the current MySQL version number. This ensures that next time you run mysql_upgrade with the same version of the server, it can tell whether there is any need to check or repair the table again.
mysql_upgrade also saves the MySQL version number in a file named mysql_upgrade.info in the data directory. This is used to quickly check if all tables have been checked for this release so that table-checking can be skipped.
To check and repair tables and to upgrade the system tables, mysql_upgrade executes the following commands:
mysqlcheck --check-upgrade --all-databases --auto-repair mysql_fix_privilege_tables
mysql_upgrade currently works only on Unix.
To use mysql_upgrade, make sure that the server is running, and then invoke it like this:
shell> mysql_upgrade
