Re: [HACKERS] [sqlsmith] Crash in GetOldestSnapshot()

2016-08-07 Thread Robert Haas
On Sun, Aug 7, 2016 at 5:46 PM, Tom Lane wrote: > Robert Haas writes: >> On Sun, Aug 7, 2016 at 2:03 PM, Tom Lane wrote: >>> What I suggested just now in <2850.1470592...@sss.pgh.pa.us> might >>> be implementable with a couple

Re: [HACKERS] [sqlsmith] Crash in GetOldestSnapshot()

2016-08-07 Thread Tom Lane
Robert Haas writes: > On Sun, Aug 7, 2016 at 2:03 PM, Tom Lane wrote: >> What I suggested just now in <2850.1470592...@sss.pgh.pa.us> might >> be implementable with a couple hours' work, though. Do you have a >> reason to think it'd be insufficient? >

Re: [HACKERS] [sqlsmith] Crash in GetOldestSnapshot()

2016-08-07 Thread Tom Lane
Robert Haas writes: > On Sun, Aug 7, 2016 at 2:03 PM, Tom Lane wrote: >> What I suggested just now in <2850.1470592...@sss.pgh.pa.us> might >> be implementable with a couple hours' work, though. Do you have a >> reason to think it'd be insufficient? >

Re: [HACKERS] [sqlsmith] Crash in GetOldestSnapshot()

2016-08-07 Thread Robert Haas
On Sun, Aug 7, 2016 at 2:03 PM, Tom Lane wrote: > Robert Haas writes: >> So I think in the short term what we should do about this is just fix >> it so it doesn't crash. > > Well, we clearly need to fix GetOldestSnapshot so it won't crash, > but I do

Re: [HACKERS] [sqlsmith] Crash in GetOldestSnapshot()

2016-08-07 Thread Robert Haas
On Sun, Aug 7, 2016 at 1:57 PM, Tom Lane wrote: > Andrew Gierth writes: >> 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

Re: [HACKERS] [sqlsmith] Crash in GetOldestSnapshot()

2016-08-07 Thread Tom Lane
Robert Haas writes: > So I think in the short term what we should do about this is just fix > it so it doesn't crash. Well, we clearly need to fix GetOldestSnapshot so it won't crash, but I do not think that having RETURNING queries randomly returning "ERROR: no known

Re: [HACKERS] [sqlsmith] Crash in GetOldestSnapshot()

2016-08-07 Thread Robert Haas
On Sat, Aug 6, 2016 at 9:00 AM, Andrew Gierth wrote: > 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

Re: [HACKERS] [sqlsmith] Crash in GetOldestSnapshot()

2016-08-07 Thread Tom Lane
Andrew Gierth writes: > 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

Re: [HACKERS] [sqlsmith] Crash in GetOldestSnapshot()

2016-08-06 Thread Andrew Gierth
> "Amit" == Amit Kapila 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

Re: [HACKERS] [sqlsmith] Crash in GetOldestSnapshot()

2016-08-06 Thread Amit Kapila
On Sat, Aug 6, 2016 at 5:51 PM, Andrew Gierth wrote: >> "Andreas" == Andreas Seltenreich writes: > > 418 if (OldestActiveSnapshot != NULL) > 419 ActiveLSN = OldestActiveSnapshot->as_snap->lsn; > 420 > 421 if

Re: [HACKERS] [sqlsmith] Crash in GetOldestSnapshot()

2016-08-06 Thread Andrew Gierth
> "Andreas" == Andreas Seltenreich writes: 418 if (OldestActiveSnapshot != NULL) 419 ActiveLSN = OldestActiveSnapshot->as_snap->lsn; 420 421 if (XLogRecPtrIsInvalid(RegisteredLSN) || RegisteredLSN > ActiveLSN) 422 return OldestActiveSnapshot->as_snap;

Re: [HACKERS] [sqlsmith] Crash in GetOldestSnapshot()

2016-08-06 Thread Michael Paquier
On Sat, Aug 6, 2016 at 6:32 PM, Andreas Seltenreich wrote: > since updating master from c93d873..fc509cd, I see crashes in > GetOldestSnapshot() on update/delete returning statements. > > I reduced the triggering statements down to this: > > update clstr_tst set d = d

[HACKERS] [sqlsmith] Crash in GetOldestSnapshot()

2016-08-06 Thread Andreas Seltenreich
Hi, since updating master from c93d873..fc509cd, I see crashes in GetOldestSnapshot() on update/delete returning statements. I reduced the triggering statements down to this: update clstr_tst set d = d returning d; Backtrace below. regards, Andreas Program received signal SIGSEGV,