Let the wrangler thread run all the time - don't bother with initialization.
Some cleanup of the Worker class, since it's gone through some changes.
Use INSERT RETURNING to have Job.queue return an instance of the appropriate job class.
Clean up the Job class after the RETURNING changes.
Make hashes indifferent when they're retrieved from the database, to keep them that way as often as possible.
Use a prepared statement to insert jobs.