A completely reasonable stance. However, it's not so much a performance question as one of concurrency. The easiest way to get the right semantics is by lockin

A completely reasonable stance. However, it's not so much a performance question as one of concurrency. The easiest way to get the right semantics is by locking the entire destination table against concurrent writes. Maybe that's fine for a lot of users. But it has caused some hesitation, because other users might be disappointed. It would be fair to say "just do it" though.