Schema change

Perhaps you are looking for:
 * Proposed Database Schema Changes
 * Schema changes &mdash; process for getting schema changes applied on Wikimedia production. Also contains some generally applicable advice on schema changes and design.
 * Manual:Hooks/LoadExtensionSchemaUpdates &mdash; a hook allowing extensions to make changes to the database when update.php is used
 * the schemas in the Schema: namespace that describe the format of events logged by extension Event logging.