For example, today we discovered that image and flaggedrevs don't have indexes on the fields we use in our queries.
- image has index on img_user_text
- filearchive has file_user_timestamp which uses fa_user_text
- oldimage has oi_usertext_timestamp which uses oi_user_text
- recentchanges has rc_user_text which uses rc_user_text
- No index for ipblocks.ipb_by