Alvaro Herrera wrote:
> Robert Haas wrote:
> > On Fri, Jun 17, 2016 at 9:33 AM, Andrew Gierth
> > <and...@tao11.riddles.org.uk> wrote:
> > >>>>>> "Robert" == Robert Haas <robertmh...@gmail.com> writes:
> > > >> Why is the correct rule not "check for and ignore pre-upgrade mxids
> > > >> before even trying to fetch members"?
> > >
> > > Robert> I entirely believe that's the correct rule, but doesn't
> > > Robert> implementing it require a crystal balll?
> > >
> > > Why would it? Pre-9.3 mxids are identified by the combination of flag
> > > bits in the infomask, see Alvaro's patch.
> >
> > I see the patch, but I don't see much explanation of why the patch is
> > correct, which I think is pretty scary in view of the number of
> > mistakes we've already made in this area.
>
> ... and actually the patch fails one isolation tests in 9.3, which is
> why I haven't pushed (I haven't tested 9.4 but I suppose it should be
> the same). I'm looking into that now.
Ah, it should have been obvious; the reason it's failing is because 9.3
and 9.4 lack commit 27846f02c176 which removed
MultiXactHasRunningRemoteMembers(), so the straight backpatch plus
conflict fixes left one GetMultiXactIdMembers call with the allow_old
flag to true. The attached patch fixes that omission.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
commit 17507b2a04b8c381997410d1fe3fbaacc34f5a31[m
Author: Alvaro Herrera <alvhe...@alvh.no-ip.org>
AuthorDate: Tue Jun 21 18:07:49 2016 -0400
CommitDate: Tue Jun 21 18:07:49 2016 -0400
fixup MultiXactHasRunningRemoteMembers
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index 15de62d..efbca6f 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -1448,7 +1448,7 @@ MultiXactHasRunningRemoteMembers(MultiXactId multi)
int nmembers;
int i;
- nmembers = GetMultiXactIdMembers(multi, &members, true);
+ nmembers = GetMultiXactIdMembers(multi, &members, false);
if (nmembers <= 0)
return false;
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 9d7050a..931e2fb 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -701,7 +701,9 @@ HeapTupleSatisfiesUpdate(HeapTupleHeader tuple, CommandId curcid,
if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
{
- if (MultiXactHasRunningRemoteMembers(xmax))
+ if (HEAP_LOCKED_UPGRADED(tuple->t_infomask))
+ return HeapTupleMayBeUpdated;
+ else if (MultiXactHasRunningRemoteMembers(xmax))
return HeapTupleBeingUpdated;
else
return HeapTupleMayBeUpdated;
@@ -725,6 +727,7 @@ HeapTupleSatisfiesUpdate(HeapTupleHeader tuple, CommandId curcid,
/* not LOCKED_ONLY, so it has to have an xmax */
Assert(TransactionIdIsValid(xmax));
+ Assert(!HEAP_LOCKED_UPGRADED(tuple->t_infomask));
/* updating subtransaction must have aborted */
if (!TransactionIdIsCurrentTransactionId(xmax))
--
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