I, uh, do want to point out that the alternative here is not "everything is OK". If you don't abort when, say, two users update the same row concurrently, then

I, uh, do want to point out that the alternative here is not "everything is OK". If you don't abort when, say, two users update the same row concurrently, then you might cause (e.g.) silent data loss for one of them. Or you might end up with a record in an illegal state--say, one with two different fields that should never be in their particular states together. You have to look at your transaction structure, intended application invariants, and measured frequency of concurrency to figure out if using a relaxed isolation level is actually safe or not.