* @return string
*/
protected function indexName( $index ) {
- // Backwards-compatibility hack
+ /**
+ * When SQLite indexes were introduced in r45764, it was noted that
+ * SQLite requires index names to be unique within the whole database,
+ * not just within a schema. As discussed in CR r45819, to avoid the
+ * need for a schema change on existing installations, the indexes
+ * were implicitly mapped from the new names to the old names.
+ *
+ * This mapping can be removed if DB patches are introduced to alter
+ * the relevant tables in existing installations. Note that because
+ * this index mapping applies to table creation, even new installations
+ * of MySQL have the old names (except for installations created during
+ * a period where this mapping was inappropriately removed, see
+ * T154872).
+ */
$renamed = [
'ar_usertext_timestamp' => 'usertext_timestamp',
'un_user_id' => 'user_id',