Re: Speed up pg_checksums in cases where checksum already set

I was originally on the fence about including this as well, but it seems like since the database is shut down and already in a consistent state, there seems no advantage to syncing if we have not made any changes. Things are no better or worse than when we arrived. However, the real-world use case of running pg_checksums --enable and getting no changed blocks is probably fairly rare, so if there is a strong objection, I'm happy reverting to just (do_sync). (I'm not sure how cheap a sync is, I assume it's low impact as the database is shut down, I guess it becomes a "might as well while we are here"?)