> - A simple typo in psql can currently cause a forced rollback of the entire
> TX. UNDO should avoid this.
Yes, I forgot to mention this very big advantage, but undo is not the only possible way
to implement savepoints. Solutions using CommandCounter have been discussed.
Although the pg_log mechanism would become more complex, a background
"vacuum-like" process could put highest priority on removing such rolled back parts
of transactions.
Andreas