I have my queue workers maintain a list of task owners they've already processed, and prefer to get a task from an owner they've least-recently seen (or haven't

I have my queue workers maintain a list of task owners they've already processed, and prefer to get a task from an owner they've least-recently seen (or haven't seen) using `ORDER BY array_position(:seen_owner_ids, owner_id) desc`. Each new task's owner_id is inserted into the front of the list (and removed elsewhere if it exists). But I have a relatively small number of possible `owner_id` values at any given time.