>>>>> "Amit" == Amit Kapila <amit.kapil...@gmail.com> writes:
Amit> Sure, that is the reason of crash, but even if we do that it will Amit> lead to an error "no known snapshots". Here, what is going on is Amit> that we initialized toast snapshot when there is no active Amit> snapshot in the backend, so GetOldestSnapshot() won't return any Amit> snapshot. Hmm. So this happens because RETURNING queries run to completion immediately and populate a tuplestore with the results, and the portal then fetches from the tuplestore to send to the destination. The assumption is that the tuplestore output can be processed without needing a snapshot, which obviously is not true now if it contains toasted data. In a similar case in the past involving holdable cursors, the solution was to detoast _before_ storing in the tuplestore (see PersistHoldablePortal). I guess the question now is, under what circumstances is it now allowable to detoast a datum with no active snapshot? (Wouldn't it be necessary in such a case to know what the oldest snapshot ever used in the transaction was?) Amit> I think for such situations, we need to initialize the lsn and Amit> whenTaken of ToastSnapshot as we do in GetSnapshotData() [1]. Would that not give a too-recent LSN, resulting in possibly failing to fetch the toast rows? -- Andrew (irc:RhodiumToad) -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
