Bare with me while I'm trying to remember all these. Are transactional callbacks only fired when the root (real) transaction is committed? I seem to remember @jeremy commenting on a ticket like that, but I couldn't find it. If that's the expected behaviour then that's fine, otherwise wouldn't this break nested transactions?

I looked at the code and it seems like we in fact do not call this on `SavepointTransaction`, so it's probably fine (and it's what it does today anyway), just want to confirm that it is expected. (Are there other adapters that actually use real nested transactions ?_?)