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Commitc29a9c3

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Fix UPDATE/DELETE WHERE CURRENT OF to support repeated update and update-
then-delete on the current cursor row. The basic fix is that nodeTidscan.chas to apply heap_get_latest_tid() to the current-scan-TID obtained from thecursor query; this ensures we get the latest row version to work with.However, since that only works if the query plan is a TID scan, we also haveto hack the planner to make sure only that type of plan will be selected.(Formerly, the planner might decide to apply a seqscan if the table is verysmall. This change is probably a Good Thing anyway, since it's hard to seehow a seqscan could really win.) That means the execQual.c code to supportCurrentOfExpr as a regular expression type is dead code, so replace it withjust an elog(). Also, add regression tests covering these cases. Notethat the added tests expose the fact that re-fetching an updated rowmisbehaves if the cursor used FOR UPDATE. That's an independent bug thatshould be fixed later. Per report from Dharmendra Goyal.
1 parent9226ba8 commitc29a9c3

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6 files changed

+225
-43
lines changed

6 files changed

+225
-43
lines changed

‎src/backend/executor/execQual.c

Lines changed: 6 additions & 34 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.222 2007/09/06 17:31:58 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.223 2007/10/24 18:37:08 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -3694,45 +3694,17 @@ ExecEvalArrayCoerceExpr(ArrayCoerceExprState *astate,
36943694
/* ----------------------------------------------------------------
36953695
*ExecEvalCurrentOfExpr
36963696
*
3697-
* Normally, the planner will convert CURRENT OF into a TidScan qualification,
3698-
* but we have plain execQual support in case it doesn't.
3697+
* The planner must convert CURRENT OF into a TidScan qualification.
3698+
* So, we have to be able to do ExecInitExpr on a CurrentOfExpr,
3699+
* but we shouldn't ever actually execute it.
36993700
* ----------------------------------------------------------------
37003701
*/
37013702
staticDatum
37023703
ExecEvalCurrentOfExpr(ExprState*exprstate,ExprContext*econtext,
37033704
bool*isNull,ExprDoneCond*isDone)
37043705
{
3705-
CurrentOfExpr*cexpr= (CurrentOfExpr*)exprstate->expr;
3706-
boolresult;
3707-
boollisnull;
3708-
Oidtableoid;
3709-
ItemPointertuple_tid;
3710-
ItemPointerDatacursor_tid;
3711-
3712-
if (isDone)
3713-
*isDone=ExprSingleResult;
3714-
*isNull= false;
3715-
3716-
Assert(cexpr->cvarno!=INNER);
3717-
Assert(cexpr->cvarno!=OUTER);
3718-
Assert(!TupIsNull(econtext->ecxt_scantuple));
3719-
/* Use slot_getattr to catch any possible mistakes */
3720-
tableoid=DatumGetObjectId(slot_getattr(econtext->ecxt_scantuple,
3721-
TableOidAttributeNumber,
3722-
&lisnull));
3723-
Assert(!lisnull);
3724-
tuple_tid= (ItemPointer)
3725-
DatumGetPointer(slot_getattr(econtext->ecxt_scantuple,
3726-
SelfItemPointerAttributeNumber,
3727-
&lisnull));
3728-
Assert(!lisnull);
3729-
3730-
if (execCurrentOf(cexpr,econtext,tableoid,&cursor_tid))
3731-
result=ItemPointerEquals(&cursor_tid,tuple_tid);
3732-
else
3733-
result= false;
3734-
3735-
returnBoolGetDatum(result);
3706+
elog(ERROR,"CURRENT OF cannot be executed");
3707+
return0;/* keep compiler quiet */
37363708
}
37373709

37383710

‎src/backend/executor/nodeTidscan.c

Lines changed: 17 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/executor/nodeTidscan.c,v 1.55 2007/06/11 22:22:40 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/executor/nodeTidscan.c,v 1.56 2007/10/24 18:37:08 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -68,6 +68,7 @@ TidListCreate(TidScanState *tidstate)
6868
tidList= (ItemPointerData*)
6969
palloc(numAllocTids*sizeof(ItemPointerData));
7070
numTids=0;
71+
tidstate->tss_isCurrentOf= false;
7172

7273
foreach(l,evalList)
7374
{
@@ -165,6 +166,7 @@ TidListCreate(TidScanState *tidstate)
165166
numAllocTids*sizeof(ItemPointerData));
166167
}
167168
tidList[numTids++]=cursor_tid;
169+
tidstate->tss_isCurrentOf= true;
168170
}
169171
}
170172
else
@@ -182,6 +184,9 @@ TidListCreate(TidScanState *tidstate)
182184
intlastTid;
183185
inti;
184186

187+
/* CurrentOfExpr could never appear OR'd with something else */
188+
Assert(!tidstate->tss_isCurrentOf);
189+
185190
qsort((void*)tidList,numTids,sizeof(ItemPointerData),
186191
itemptr_comparator);
187192
lastTid=0;
@@ -269,7 +274,8 @@ TidNext(TidScanState *node)
269274

270275
/*
271276
* XXX shouldn't we check here to make sure tuple matches TID list? In
272-
* runtime-key case this is not certain, is it?
277+
* runtime-key case this is not certain, is it? However, in the
278+
* WHERE CURRENT OF case it might not match anyway ...
273279
*/
274280

275281
ExecStoreTuple(estate->es_evTuple[scanrelid-1],
@@ -319,6 +325,15 @@ TidNext(TidScanState *node)
319325
while (node->tss_TidPtr >=0&&node->tss_TidPtr<numTids)
320326
{
321327
tuple->t_self=tidList[node->tss_TidPtr];
328+
329+
/*
330+
* For WHERE CURRENT OF, the tuple retrieved from the cursor might
331+
* since have been updated; if so, we should fetch the version that
332+
* is current according to our snapshot.
333+
*/
334+
if (node->tss_isCurrentOf)
335+
heap_get_latest_tid(heapRelation,snapshot,&tuple->t_self);
336+
322337
if (heap_fetch(heapRelation,snapshot,tuple,&buffer, false,NULL))
323338
{
324339
/*

‎src/backend/optimizer/path/costsize.c

Lines changed: 26 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -54,7 +54,7 @@
5454
* Portions Copyright (c) 1994, Regents of the University of California
5555
*
5656
* IDENTIFICATION
57-
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.186 2007/09/22 21:36:40 tgl Exp $
57+
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.187 2007/10/24 18:37:08 tgl Exp $
5858
*
5959
*-------------------------------------------------------------------------
6060
*/
@@ -769,6 +769,7 @@ cost_tidscan(Path *path, PlannerInfo *root,
769769
{
770770
Coststartup_cost=0;
771771
Costrun_cost=0;
772+
boolisCurrentOf= false;
772773
Costcpu_per_tuple;
773774
QualCosttid_qual_cost;
774775
intntuples;
@@ -778,9 +779,6 @@ cost_tidscan(Path *path, PlannerInfo *root,
778779
Assert(baserel->relid>0);
779780
Assert(baserel->rtekind==RTE_RELATION);
780781

781-
if (!enable_tidscan)
782-
startup_cost+=disable_cost;
783-
784782
/* Count how many tuples we expect to retrieve */
785783
ntuples=0;
786784
foreach(l,tidquals)
@@ -793,13 +791,35 @@ cost_tidscan(Path *path, PlannerInfo *root,
793791

794792
ntuples+=estimate_array_length(arraynode);
795793
}
794+
elseif (IsA(lfirst(l),CurrentOfExpr))
795+
{
796+
/* CURRENT OF yields 1 tuple */
797+
isCurrentOf= true;
798+
ntuples++;
799+
}
796800
else
797801
{
798802
/* It's just CTID = something, count 1 tuple */
799803
ntuples++;
800804
}
801805
}
802806

807+
/*
808+
* We must force TID scan for WHERE CURRENT OF, because only nodeTidscan.c
809+
* understands how to do it correctly. Therefore, honor enable_tidscan
810+
* only when CURRENT OF isn't present. Also note that cost_qual_eval
811+
* counts a CurrentOfExpr as having startup cost disable_cost, which we
812+
* subtract off here; that's to prevent other plan types such as seqscan
813+
* from winning.
814+
*/
815+
if (isCurrentOf)
816+
{
817+
Assert(baserel->baserestrictcost.startup >=disable_cost);
818+
startup_cost-=disable_cost;
819+
}
820+
elseif (!enable_tidscan)
821+
startup_cost+=disable_cost;
822+
803823
/*
804824
* The TID qual expressions will be computed once, any other baserestrict
805825
* quals once per retrived tuple.
@@ -2002,8 +2022,8 @@ cost_qual_eval_walker(Node *node, cost_qual_eval_context *context)
20022022
}
20032023
elseif (IsA(node,CurrentOfExpr))
20042024
{
2005-
/*This is noticeably more expensive than a typical operator */
2006-
context->total.per_tuple+=100*cpu_operator_cost;
2025+
/*Report high cost to prevent selection of anything but TID scan */
2026+
context->total.startup+=disable_cost;
20072027
}
20082028
elseif (IsA(node,SubLink))
20092029
{

‎src/include/nodes/execnodes.h

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.178 2007/09/20 17:56:32 tgl Exp $
10+
* $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.179 2007/10/24 18:37:08 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -1087,6 +1087,7 @@ typedef struct BitmapHeapScanState
10871087
/* ----------------
10881088
* TidScanState information
10891089
*
1090+
*isCurrentOf scan has a CurrentOfExpr qual
10901091
*NumTids number of tids in this scan
10911092
*TidPtr index of currently fetched tid
10921093
*TidList evaluated item pointers (array of size NumTids)
@@ -1096,6 +1097,7 @@ typedef struct TidScanState
10961097
{
10971098
ScanStatess;/* its first field is NodeTag */
10981099
List*tss_tidquals;/* list of ExprState nodes */
1100+
booltss_isCurrentOf;
10991101
inttss_NumTids;
11001102
inttss_TidPtr;
11011103
inttss_MarkTidPtr;

‎src/test/regress/expected/portals.out

Lines changed: 133 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -982,6 +982,139 @@ SELECT * FROM uctest;
982982
8 | one
983983
(2 rows)
984984

985+
-- Check repeated-update and update-then-delete cases
986+
BEGIN;
987+
DECLARE c1 CURSOR FOR SELECT * FROM uctest;
988+
FETCH c1;
989+
f1 | f2
990+
----+-------
991+
3 | three
992+
(1 row)
993+
994+
UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1;
995+
SELECT * FROM uctest;
996+
f1 | f2
997+
----+-------
998+
8 | one
999+
13 | three
1000+
(2 rows)
1001+
1002+
UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1;
1003+
SELECT * FROM uctest;
1004+
f1 | f2
1005+
----+-------
1006+
8 | one
1007+
23 | three
1008+
(2 rows)
1009+
1010+
-- insensitive cursor should not show effects of updates or deletes
1011+
FETCH RELATIVE 0 FROM c1;
1012+
f1 | f2
1013+
----+-------
1014+
3 | three
1015+
(1 row)
1016+
1017+
DELETE FROM uctest WHERE CURRENT OF c1;
1018+
SELECT * FROM uctest;
1019+
f1 | f2
1020+
----+-----
1021+
8 | one
1022+
(1 row)
1023+
1024+
DELETE FROM uctest WHERE CURRENT OF c1; -- no-op
1025+
SELECT * FROM uctest;
1026+
f1 | f2
1027+
----+-----
1028+
8 | one
1029+
(1 row)
1030+
1031+
UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1; -- no-op
1032+
SELECT * FROM uctest;
1033+
f1 | f2
1034+
----+-----
1035+
8 | one
1036+
(1 row)
1037+
1038+
FETCH RELATIVE 0 FROM c1;
1039+
f1 | f2
1040+
----+-------
1041+
3 | three
1042+
(1 row)
1043+
1044+
ROLLBACK;
1045+
SELECT * FROM uctest;
1046+
f1 | f2
1047+
----+-------
1048+
3 | three
1049+
8 | one
1050+
(2 rows)
1051+
1052+
BEGIN;
1053+
DECLARE c1 CURSOR FOR SELECT * FROM uctest FOR UPDATE;
1054+
FETCH c1;
1055+
f1 | f2
1056+
----+-------
1057+
3 | three
1058+
(1 row)
1059+
1060+
UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1;
1061+
SELECT * FROM uctest;
1062+
f1 | f2
1063+
----+-------
1064+
8 | one
1065+
13 | three
1066+
(2 rows)
1067+
1068+
UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1;
1069+
SELECT * FROM uctest;
1070+
f1 | f2
1071+
----+-------
1072+
8 | one
1073+
23 | three
1074+
(2 rows)
1075+
1076+
-- sensitive cursor should show effects of updates or deletes
1077+
-- XXX current behavior is WRONG
1078+
FETCH RELATIVE 0 FROM c1;
1079+
f1 | f2
1080+
----+-----
1081+
8 | one
1082+
(1 row)
1083+
1084+
DELETE FROM uctest WHERE CURRENT OF c1;
1085+
SELECT * FROM uctest;
1086+
f1 | f2
1087+
----+-------
1088+
23 | three
1089+
(1 row)
1090+
1091+
DELETE FROM uctest WHERE CURRENT OF c1; -- no-op
1092+
SELECT * FROM uctest;
1093+
f1 | f2
1094+
----+-------
1095+
23 | three
1096+
(1 row)
1097+
1098+
UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1; -- no-op
1099+
SELECT * FROM uctest;
1100+
f1 | f2
1101+
----+-------
1102+
23 | three
1103+
(1 row)
1104+
1105+
FETCH RELATIVE 0 FROM c1;
1106+
f1 | f2
1107+
----+----
1108+
(0 rows)
1109+
1110+
ROLLBACK;
1111+
SELECT * FROM uctest;
1112+
f1 | f2
1113+
----+-------
1114+
3 | three
1115+
8 | one
1116+
(2 rows)
1117+
9851118
-- Check inheritance cases
9861119
CREATE TEMP TABLE ucchild () inherits (uctest);
9871120
INSERT INTO ucchild values(100, 'hundred');

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