I have tried to upgrade the MW version from 1.21 to 1.35
The update (update.php) fails.
The error is in the script patch-drop-image-user-fields.sql
The script tries to replace an index with the name img_user_timestamp. But this is called img_actor_timestamp;
ALTER TABLE `image` DROP INDEX img_actor_timestamp, DROP INDEX img_usertext_timestamp, DROP COLUMN img_user, DROP COLUMN img_user_text, ALTER COLUMN img_actor DROP DEFAULT;