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Commit4c77cbb

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committed
PortalRun must guard against the possibility that the portal it's
running contains VACUUM or a similar command that will internally startand commit transactions. In such a case, the original caller values ofCurrentMemoryContext and CurrentResourceOwner will point to objects thatwill be destroyed by the internal commit. We must restore these pointersto point to the newly-manufactured transaction context and resource owner,rather than possibly pointing to deleted memory.Also tweak xact.c so that AbortTransaction and AbortSubTransactionforcibly restore a sane value for CurrentResourceOwner, much as theyhave always done for CurrentMemoryContext. I'm not certain this isnecessary but I'm feeling paranoid today.Responds to Sean Chittenden's bug report of 4-Oct.
1 parentee7de3d commit4c77cbb

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2 files changed

+68
-10
lines changed

2 files changed

+68
-10
lines changed

‎src/backend/access/transam/xact.c

Lines changed: 33 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -10,7 +10,7 @@
1010
*
1111
*
1212
* IDENTIFICATION
13-
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.190 2004/09/16 20:17:16 tgl Exp $
13+
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.191 2004/10/04 21:52:14 tgl Exp $
1414
*
1515
*-------------------------------------------------------------------------
1616
*/
@@ -205,6 +205,7 @@ static void AssignSubTransactionId(TransactionState s);
205205
staticvoidAbortTransaction(void);
206206
staticvoidAtAbort_Memory(void);
207207
staticvoidAtCleanup_Memory(void);
208+
staticvoidAtAbort_ResourceOwner(void);
208209
staticvoidAtCommit_LocalCache(void);
209210
staticvoidAtCommit_Memory(void);
210211
staticvoidAtStart_Cache(void);
@@ -229,6 +230,7 @@ static void PopTransaction(void);
229230

230231
staticvoidAtSubAbort_Memory(void);
231232
staticvoidAtSubCleanup_Memory(void);
233+
staticvoidAtSubAbort_ResourceOwner(void);
232234
staticvoidAtSubCommit_Memory(void);
233235
staticvoidAtSubStart_Memory(void);
234236
staticvoidAtSubStart_ResourceOwner(void);
@@ -1103,7 +1105,6 @@ AtAbort_Memory(void)
11031105
MemoryContextSwitchTo(TopMemoryContext);
11041106
}
11051107

1106-
11071108
/*
11081109
* AtSubAbort_Memory
11091110
*/
@@ -1115,6 +1116,33 @@ AtSubAbort_Memory(void)
11151116
MemoryContextSwitchTo(TopTransactionContext);
11161117
}
11171118

1119+
1120+
/*
1121+
*AtAbort_ResourceOwner
1122+
*/
1123+
staticvoid
1124+
AtAbort_ResourceOwner(void)
1125+
{
1126+
/*
1127+
* Make sure we have a valid ResourceOwner, if possible (else it
1128+
* will be NULL, which is OK)
1129+
*/
1130+
CurrentResourceOwner=TopTransactionResourceOwner;
1131+
}
1132+
1133+
/*
1134+
* AtSubAbort_ResourceOwner
1135+
*/
1136+
staticvoid
1137+
AtSubAbort_ResourceOwner(void)
1138+
{
1139+
TransactionStates=CurrentTransactionState;
1140+
1141+
/* Make sure we have a valid ResourceOwner */
1142+
CurrentResourceOwner=s->curTransactionOwner;
1143+
}
1144+
1145+
11181146
/*
11191147
* AtSubAbort_childXids
11201148
*/
@@ -1598,8 +1626,9 @@ AbortTransaction(void)
15981626
*/
15991627
s->state=TRANS_ABORT;
16001628

1601-
/* Make sure weare ina valid memory context */
1629+
/* Make sure wehavea valid memory context and resource owner */
16021630
AtAbort_Memory();
1631+
AtAbort_ResourceOwner();
16031632

16041633
/*
16051634
* Reset user id which might have been changed transiently. We cannot
@@ -3338,6 +3367,7 @@ AbortSubTransaction(void)
33383367
* do abort processing
33393368
*/
33403369
AtSubAbort_Memory();
3370+
AtSubAbort_ResourceOwner();
33413371

33423372
/*
33433373
* We can skip all this stuff if the subxact failed before creating

‎src/backend/tcop/pquery.c

Lines changed: 35 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/tcop/pquery.c,v 1.87 2004/09/13 20:07:05 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/tcop/pquery.c,v 1.88 2004/10/04 21:52:15 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -491,12 +491,14 @@ PortalRun(Portal portal, long count,
491491
char*completionTag)
492492
{
493493
boolresult;
494+
ResourceOwnersaveTopTransactionResourceOwner;
495+
MemoryContextsaveTopTransactionContext;
494496
PortalsaveActivePortal;
495497
SnapshotsaveActiveSnapshot;
496498
ResourceOwnersaveResourceOwner;
497499
MemoryContextsavePortalContext;
498500
MemoryContextsaveQueryContext;
499-
MemoryContextoldContext;
501+
MemoryContextsaveMemoryContext;
500502

501503
AssertArg(PortalIsValid(portal));
502504

@@ -523,12 +525,26 @@ PortalRun(Portal portal, long count,
523525

524526
/*
525527
* Set up global portal context pointers.
528+
*
529+
* We have to play a special game here to support utility commands like
530+
* VACUUM and CLUSTER, which internally start and commit transactions.
531+
* When we are called to execute such a command, CurrentResourceOwner
532+
* will be pointing to the TopTransactionResourceOwner --- which will
533+
* be destroyed and replaced in the course of the internal commit and
534+
* restart. So we need to be prepared to restore it as pointing to
535+
* the exit-time TopTransactionResourceOwner. (Ain't that ugly? This
536+
* idea of internally starting whole new transactions is not good.)
537+
* CurrentMemoryContext has a similar problem, but the other pointers
538+
* we save here will be NULL or pointing to longer-lived objects.
526539
*/
540+
saveTopTransactionResourceOwner=TopTransactionResourceOwner;
541+
saveTopTransactionContext=TopTransactionContext;
527542
saveActivePortal=ActivePortal;
528543
saveActiveSnapshot=ActiveSnapshot;
529544
saveResourceOwner=CurrentResourceOwner;
530545
savePortalContext=PortalContext;
531546
saveQueryContext=QueryContext;
547+
saveMemoryContext=CurrentMemoryContext;
532548
PG_TRY();
533549
{
534550
ActivePortal=portal;
@@ -537,7 +553,7 @@ PortalRun(Portal portal, long count,
537553
PortalContext=PortalGetHeapMemory(portal);
538554
QueryContext=portal->queryContext;
539555

540-
oldContext=MemoryContextSwitchTo(PortalContext);
556+
MemoryContextSwitchTo(PortalContext);
541557

542558
switch (portal->strategy)
543559
{
@@ -620,21 +636,33 @@ PortalRun(Portal portal, long count,
620636
portal->status=PORTAL_FAILED;
621637

622638
/* Restore global vars and propagate error */
639+
if (saveMemoryContext==saveTopTransactionContext)
640+
MemoryContextSwitchTo(TopTransactionContext);
641+
else
642+
MemoryContextSwitchTo(saveMemoryContext);
623643
ActivePortal=saveActivePortal;
624644
ActiveSnapshot=saveActiveSnapshot;
625-
CurrentResourceOwner=saveResourceOwner;
645+
if (saveResourceOwner==saveTopTransactionResourceOwner)
646+
CurrentResourceOwner=TopTransactionResourceOwner;
647+
else
648+
CurrentResourceOwner=saveResourceOwner;
626649
PortalContext=savePortalContext;
627650
QueryContext=saveQueryContext;
628651

629652
PG_RE_THROW();
630653
}
631654
PG_END_TRY();
632655

633-
MemoryContextSwitchTo(oldContext);
634-
656+
if (saveMemoryContext==saveTopTransactionContext)
657+
MemoryContextSwitchTo(TopTransactionContext);
658+
else
659+
MemoryContextSwitchTo(saveMemoryContext);
635660
ActivePortal=saveActivePortal;
636661
ActiveSnapshot=saveActiveSnapshot;
637-
CurrentResourceOwner=saveResourceOwner;
662+
if (saveResourceOwner==saveTopTransactionResourceOwner)
663+
CurrentResourceOwner=TopTransactionResourceOwner;
664+
else
665+
CurrentResourceOwner=saveResourceOwner;
638666
PortalContext=savePortalContext;
639667
QueryContext=saveQueryContext;
640668

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