Greg Stark <[EMAIL PROTECTED]> writes: > This is presumably because of the long-standing issue that Postgres takes the > snapshot as soon as the BEGIN is issued.
No, we don't set the snapshot until the first DML query is issued. This is critical for serializable transactions: you have to be able to take locks before the snapshot is frozen. There are at least three interesting events involved: 1 BEGIN command issued 2 First lock taken (presumably as a consequence of another command) 3 Transaction snapshot taken (ditto; might be a different command) We have to start the transaction no later than event #2 since there has to be something to hold the lock. But it'd be easy enough to decouple this from BEGIN, and it'd be good enough to solve the "COMMIT;BEGIN" problem. Which of these three times do you think now() ought to correspond to? I recall having argued that it should be event #3 since that corresponds to the database snapshot you see. 100% backwards compatibility would require setting now() at event #1, but will anyone weep if we change that? regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])