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Commitc778f89

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The previous fix in CVS HEAD and 8.4 for handling the case where a cursor
being used in a PL/pgSQL FOR loop is closed was inadequate, as Tom Lanepointed out. The bug affects FOR statement variants too, because you canclose an implicitly created cursor too by guessing the "<unnamed portal X>"name created for it.To fix that, "pin" the portal to prevent it from being dropped while it'sbeing used in a PL/pgSQL FOR loop. Backpatch all the way to 7.4 which isthe oldest supported version.
1 parent971e110 commitc778f89

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3 files changed

+67
-8
lines changed

3 files changed

+67
-8
lines changed

‎src/backend/utils/mmgr/portalmem.c

Lines changed: 49 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -12,7 +12,7 @@
1212
* Portions Copyright (c) 1994, Regents of the University of California
1313
*
1414
* IDENTIFICATION
15-
* $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.76.4.2 2005/04/11 19:51:31 tgl Exp $
15+
* $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.76.4.3 2010/07/05 09:27:49 heikki Exp $
1616
*
1717
*-------------------------------------------------------------------------
1818
*/
@@ -295,6 +295,28 @@ PortalCreateHoldStore(Portal portal)
295295
MemoryContextSwitchTo(oldcxt);
296296
}
297297

298+
/*
299+
* PinPortal
300+
*Protect a portal from dropping.
301+
*/
302+
void
303+
PinPortal(Portalportal)
304+
{
305+
if (portal->portalPinned)
306+
elog(ERROR,"portal already pinned");
307+
308+
portal->portalPinned= true;
309+
}
310+
311+
void
312+
UnpinPortal(Portalportal)
313+
{
314+
if (!portal->portalPinned)
315+
elog(ERROR,"portal not pinned");
316+
317+
portal->portalPinned= false;
318+
}
319+
298320
/*
299321
* PortalDrop
300322
*Destroy the portal.
@@ -304,9 +326,16 @@ PortalDrop(Portal portal, bool isTopCommit)
304326
{
305327
AssertArg(PortalIsValid(portal));
306328

307-
/* Not sure if this case can validly happen or not... */
308-
if (portal->status==PORTAL_ACTIVE)
309-
elog(ERROR,"cannot drop active portal");
329+
/*
330+
* Don't allow dropping a pinned portal, it's still needed by whoever
331+
* pinned it. Not sure if the PORTAL_ACTIVE case can validly happen or
332+
* not...
333+
*/
334+
if (portal->portalPinned||
335+
portal->status==PORTAL_ACTIVE)
336+
ereport(ERROR,
337+
(errcode(ERRCODE_INVALID_CURSOR_STATE),
338+
errmsg("cannot drop active portal \"%s\"",portal->name)));
310339

311340
/*
312341
* Remove portal from hash table. Because we do this first, we will
@@ -507,6 +536,13 @@ AtCommit_Portals(void)
507536
continue;
508537
}
509538

539+
/*
540+
* There should be no pinned portals anymore. Complain if someone
541+
* leaked one.
542+
*/
543+
if (portal->portalPinned)
544+
elog(ERROR,"cannot commit while a portal is pinned");
545+
510546
/*
511547
* Do nothing to cursors held over from a previous transaction
512548
* (including holdable ones just frozen by CommitHoldablePortals).
@@ -590,7 +626,15 @@ AtCleanup_Portals(void)
590626
continue;
591627
}
592628

593-
/* Else zap it. */
629+
/*
630+
* If a portal is still pinned, forcibly unpin it. PortalDrop will
631+
* not let us drop the portal otherwise. Whoever pinned the portal
632+
* was interrupted by the abort too and won't try to use it anymore.
633+
*/
634+
if (portal->portalPinned)
635+
portal->portalPinned= false;
636+
637+
/* Zap it. */
594638
PortalDrop(portal, false);
595639
}
596640
}

‎src/include/utils/portal.h

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -39,7 +39,7 @@
3939
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
4040
* Portions Copyright (c) 1994, Regents of the University of California
4141
*
42-
* $PostgreSQL: pgsql/src/include/utils/portal.h,v 1.54.4.1 2005/04/11 19:51:32 tgl Exp $
42+
* $PostgreSQL: pgsql/src/include/utils/portal.h,v 1.54.4.2 2010/07/05 09:27:49 heikki Exp $
4343
*
4444
*-------------------------------------------------------------------------
4545
*/
@@ -135,6 +135,7 @@ typedef struct PortalData
135135
/* Status data */
136136
PortalStatusstatus;/* see above */
137137
boolportalUtilReady;/* PortalRunUtility complete? */
138+
boolportalPinned;/* a pinned portal can't be dropped */
138139

139140
/* If not NULL, Executor is active; call ExecutorEnd eventually: */
140141
QueryDesc*queryDesc;/* info needed for executor invocation */
@@ -195,6 +196,8 @@ extern void AtSubAbort_Portals(SubTransactionId mySubid,
195196
externvoidAtSubCleanup_Portals(SubTransactionIdmySubid);
196197
externPortalCreatePortal(constchar*name,boolallowDup,booldupSilent);
197198
externPortalCreateNewPortal(void);
199+
externvoidPinPortal(Portalportal);
200+
externvoidUnpinPortal(Portalportal);
198201
externvoidPortalDrop(Portalportal,boolisTopCommit);
199202
externvoidDropDependentPortals(MemoryContextqueryContext);
200203
externPortalGetPortalByName(constchar*name);

‎src/pl/plpgsql/src/pl_exec.c

Lines changed: 14 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
* procedural language
44
*
55
* IDENTIFICATION
6-
* $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.127.4.8 2010/02/12 19:38:15 tgl Exp $
6+
* $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.127.4.9 2010/07/05 09:27:49 heikki Exp $
77
*
88
* This software is copyrighted by Jan Wieck - Hamburg.
99
*
@@ -1525,9 +1525,11 @@ exec_stmt_fors(PLpgSQL_execstate *estate, PLpgSQL_stmt_fors *stmt)
15251525

15261526
/*
15271527
* Open the implicit cursor for the statement and fetch the initial 10
1528-
* rows.
1528+
* rows. Pin the portal to make sure it doesn't get closed by the user
1529+
* statements we execute.
15291530
*/
15301531
exec_run_select(estate,stmt->query,0,&portal);
1532+
PinPortal(portal);
15311533

15321534
SPI_cursor_fetch(portal, true,10);
15331535
tuptab=SPI_tuptable;
@@ -1566,6 +1568,7 @@ exec_stmt_fors(PLpgSQL_execstate *estate, PLpgSQL_stmt_fors *stmt)
15661568
* (This code should match the code after the loop.)
15671569
*/
15681570
SPI_freetuptable(tuptab);
1571+
UnpinPortal(portal);
15691572
SPI_cursor_close(portal);
15701573
exec_set_found(estate,found);
15711574

@@ -1612,6 +1615,7 @@ exec_stmt_fors(PLpgSQL_execstate *estate, PLpgSQL_stmt_fors *stmt)
16121615
/*
16131616
* Close the implicit cursor
16141617
*/
1618+
UnpinPortal(portal);
16151619
SPI_cursor_close(portal);
16161620

16171621
/*
@@ -2415,6 +2419,12 @@ exec_stmt_dynfors(PLpgSQL_execstate *estate, PLpgSQL_stmt_dynfors *stmt)
24152419
pfree(querystr);
24162420
SPI_freeplan(plan);
24172421

2422+
/*
2423+
* Make sure the portal doesn't get closed by the user statements
2424+
* we execute.
2425+
*/
2426+
PinPortal(portal);
2427+
24182428
/*
24192429
* Fetch the initial 10 tuples
24202430
*/
@@ -2455,6 +2465,7 @@ exec_stmt_dynfors(PLpgSQL_execstate *estate, PLpgSQL_stmt_dynfors *stmt)
24552465
* (This code should match the code after the loop.)
24562466
*/
24572467
SPI_freetuptable(tuptab);
2468+
UnpinPortal(portal);
24582469
SPI_cursor_close(portal);
24592470
exec_set_found(estate,found);
24602471

@@ -2501,6 +2512,7 @@ exec_stmt_dynfors(PLpgSQL_execstate *estate, PLpgSQL_stmt_dynfors *stmt)
25012512
/*
25022513
* Close the implicit cursor
25032514
*/
2515+
UnpinPortal(portal);
25042516
SPI_cursor_close(portal);
25052517

25062518
/*

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