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Commit7d6e6e2

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Fix PREPARE TRANSACTION to reject the case where the transaction has dropped a
temporary table; we can't support that because there's no way to clean up thesource backend's internal state if the eventual COMMIT PREPARED is done byanother backend. This was checked correctly in 8.1 but I broke it in 8.2 :-(.Patch by Heikki Linnakangas, original trouble report by John Smith.
1 parent9b8a93b commit7d6e6e2

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6 files changed

+49
-56
lines changed

6 files changed

+49
-56
lines changed

‎src/backend/access/heap/heapam.c‎

Lines changed: 13 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.249 2008/01/30 18:35:55 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.250 2008/03/04 19:54:06 tgl Exp $
1212
*
1313
*
1414
* INTERFACE ROUTINES
@@ -868,6 +868,10 @@ relation_open(Oid relationId, LOCKMODE lockmode)
868868
if (!RelationIsValid(r))
869869
elog(ERROR,"could not open relation with OID %u",relationId);
870870

871+
/* Make note that we've accessed a temporary relation */
872+
if (r->rd_istemp)
873+
MyXactAccessedTempRel= true;
874+
871875
pgstat_initstats(r);
872876

873877
returnr;
@@ -912,6 +916,10 @@ try_relation_open(Oid relationId, LOCKMODE lockmode)
912916
if (!RelationIsValid(r))
913917
elog(ERROR,"could not open relation with OID %u",relationId);
914918

919+
/* Make note that we've accessed a temporary relation */
920+
if (r->rd_istemp)
921+
MyXactAccessedTempRel= true;
922+
915923
pgstat_initstats(r);
916924

917925
returnr;
@@ -958,6 +966,10 @@ relation_open_nowait(Oid relationId, LOCKMODE lockmode)
958966
if (!RelationIsValid(r))
959967
elog(ERROR,"could not open relation with OID %u",relationId);
960968

969+
/* Make note that we've accessed a temporary relation */
970+
if (r->rd_istemp)
971+
MyXactAccessedTempRel= true;
972+
961973
pgstat_initstats(r);
962974

963975
returnr;

‎src/backend/access/transam/xact.c‎

Lines changed: 29 additions & 1 deletion
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 1.257 2008/01/15 18:56:59 tgl Exp $
13+
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.258 2008/03/04 19:54:06 tgl Exp $
1414
*
1515
*-------------------------------------------------------------------------
1616
*/
@@ -62,6 +62,13 @@ boolXactSyncCommit = true;
6262
intCommitDelay=0;/* precommit delay in microseconds */
6363
intCommitSiblings=5;/* # concurrent xacts needed to sleep */
6464

65+
/*
66+
* MyXactAccessedTempRel is set when a temporary relation is accessed.
67+
* We don't allow PREPARE TRANSACTION in that case. (This is global
68+
* so that it can be set from heapam.c.)
69+
*/
70+
boolMyXactAccessedTempRel= false;
71+
6572

6673
/*
6774
*transaction states - transaction state from server perspective
@@ -1445,6 +1452,7 @@ StartTransaction(void)
14451452
XactIsoLevel=DefaultXactIsoLevel;
14461453
XactReadOnly=DefaultXactReadOnly;
14471454
forceSyncCommit= false;
1455+
MyXactAccessedTempRel= false;
14481456

14491457
/*
14501458
* reinitialize within-transaction counters
@@ -1770,6 +1778,26 @@ PrepareTransaction(void)
17701778

17711779
/* NOTIFY and flatfiles will be handled below */
17721780

1781+
/*
1782+
* Don't allow PREPARE TRANSACTION if we've accessed a temporary table
1783+
* in this transaction. Having the prepared xact hold locks on another
1784+
* backend's temp table seems a bad idea --- for instance it would prevent
1785+
* the backend from exiting. There are other problems too, such as how
1786+
* to clean up the source backend's local buffers and ON COMMIT state
1787+
* if the prepared xact includes a DROP of a temp table.
1788+
*
1789+
* We must check this after executing any ON COMMIT actions, because
1790+
* they might still access a temp relation.
1791+
*
1792+
* XXX In principle this could be relaxed to allow some useful special
1793+
* cases, such as a temp table created and dropped all within the
1794+
* transaction. That seems to require much more bookkeeping though.
1795+
*/
1796+
if (MyXactAccessedTempRel)
1797+
ereport(ERROR,
1798+
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1799+
errmsg("cannot PREPARE a transaction that has operated on temporary tables")));
1800+
17731801
/* Prevent cancel/die interrupt while cleaning up */
17741802
HOLD_INTERRUPTS();
17751803

‎src/backend/storage/lmgr/lmgr.c‎

Lines changed: 1 addition & 41 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.96 2008/01/08 23:18:50 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.97 2008/03/04 19:54:06 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -19,12 +19,10 @@
1919
#include"access/transam.h"
2020
#include"access/xact.h"
2121
#include"catalog/catalog.h"
22-
#include"catalog/namespace.h"
2322
#include"miscadmin.h"
2423
#include"storage/lmgr.h"
2524
#include"storage/procarray.h"
2625
#include"utils/inval.h"
27-
#include"utils/lsyscache.h"
2826

2927

3028
/*
@@ -663,44 +661,6 @@ UnlockSharedObject(Oid classid, Oid objid, uint16 objsubid,
663661
}
664662

665663

666-
/*
667-
* LockTagIsTemp
668-
*Determine whether a locktag is for a lock on a temporary object
669-
*
670-
* We need this because 2PC cannot deal with temp objects
671-
*/
672-
bool
673-
LockTagIsTemp(constLOCKTAG*tag)
674-
{
675-
switch ((LockTagType)tag->locktag_type)
676-
{
677-
caseLOCKTAG_RELATION:
678-
caseLOCKTAG_RELATION_EXTEND:
679-
caseLOCKTAG_PAGE:
680-
caseLOCKTAG_TUPLE:
681-
/* check for lock on a temp relation */
682-
/* field1 is dboid, field2 is reloid for all of these */
683-
if ((Oid)tag->locktag_field1==InvalidOid)
684-
return false;/* shared, so not temp */
685-
if (isTempOrToastNamespace(get_rel_namespace((Oid)tag->locktag_field2)))
686-
return true;
687-
break;
688-
caseLOCKTAG_TRANSACTION:
689-
caseLOCKTAG_VIRTUALTRANSACTION:
690-
/* there are no temp transactions */
691-
break;
692-
caseLOCKTAG_OBJECT:
693-
/* there are currently no non-table temp objects */
694-
break;
695-
caseLOCKTAG_USERLOCK:
696-
caseLOCKTAG_ADVISORY:
697-
/* assume these aren't temp */
698-
break;
699-
}
700-
return false;/* default case */
701-
}
702-
703-
704664
/*
705665
* Append a description of a lockable object to buf.
706666
*

‎src/backend/storage/lmgr/lock.c‎

Lines changed: 1 addition & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.181 2008/02/02 22:26:17 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.182 2008/03/04 19:54:06 tgl Exp $
1212
*
1313
* NOTES
1414
* A lock table is a shared memory hash table. When
@@ -37,7 +37,6 @@
3737
#include"access/twophase_rmgr.h"
3838
#include"miscadmin.h"
3939
#include"pgstat.h"
40-
#include"storage/lmgr.h"
4140
#include"utils/memutils.h"
4241
#include"utils/ps_status.h"
4342
#include"utils/resowner.h"
@@ -1871,12 +1870,6 @@ AtPrepare_Locks(void)
18711870
elog(ERROR,"cannot PREPARE when session locks exist");
18721871
}
18731872

1874-
/* Can't handle it if the lock is on a temporary object */
1875-
if (LockTagIsTemp(&locallock->tag.lock))
1876-
ereport(ERROR,
1877-
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1878-
errmsg("cannot PREPARE a transaction that has operated on temporary tables")));
1879-
18801873
/*
18811874
* Create a 2PC record.
18821875
*/

‎src/include/access/xact.h‎

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/access/xact.h,v 1.93 2008/01/01 19:45:56 momjian Exp $
10+
* $PostgreSQL: pgsql/src/include/access/xact.h,v 1.94 2008/03/04 19:54:06 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -44,6 +44,9 @@ extern bool XactReadOnly;
4444
/* Asynchronous commits */
4545
externboolXactSyncCommit;
4646

47+
/* Kluge for 2PC support */
48+
externboolMyXactAccessedTempRel;
49+
4750
/*
4851
*start- and end-of-transaction callbacks for dynamically loaded modules
4952
*/

‎src/include/storage/lmgr.h‎

Lines changed: 1 addition & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/storage/lmgr.h,v 1.60 2008/01/01 19:45:59 momjian Exp $
10+
* $PostgreSQL: pgsql/src/include/storage/lmgr.h,v 1.61 2008/03/04 19:54:06 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -72,9 +72,6 @@ extern void LockSharedObject(Oid classid, Oid objid, uint16 objsubid,
7272
externvoidUnlockSharedObject(Oidclassid,Oidobjid,uint16objsubid,
7373
LOCKMODElockmode);
7474

75-
/* Knowledge about which locktags describe temp objects */
76-
externboolLockTagIsTemp(constLOCKTAG*tag);
77-
7875
/* Describe a locktag for error messages */
7976
externvoidDescribeLockTag(StringInfobuf,constLOCKTAG*tag);
8077

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