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Commit493f726

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Renumber SnapshotNow and the other special snapshot codes so that
((Snapshot) NULL) can no longer be confused with a valid snapshot,as per my recent suggestion. Define a macro InvalidSnapshot for 0.Use InvalidSnapshot instead of SnapshotAny as the do-nothing specialcase for heap_update and heap_delete crosschecks; this seems a littlecleaner even though the behavior is really the same.
1 parent9835944 commit493f726

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5 files changed

+38
-20
lines changed

5 files changed

+38
-20
lines changed

‎src/backend/access/heap/heapam.c‎

Lines changed: 11 additions & 9 deletions
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 1.173 2004/08/29 05:06:40 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.174 2004/09/11 18:28:32 tgl Exp $
1212
*
1313
*
1414
* INTERFACE ROUTINES
@@ -1262,7 +1262,7 @@ simple_heap_insert(Relation relation, HeapTuple tup)
12621262
*tid - TID of tuple to be deleted
12631263
*ctid - output parameter, used only for failure case (see below)
12641264
*cid - delete command ID to use in verifying tuple visibility
1265-
*crosscheck - if notSnapshotAny, also check tuple against this
1265+
*crosscheck - if notInvalidSnapshot, also check tuple against this
12661266
*wait - true if should wait for any conflicting update to commit/abort
12671267
*
12681268
* Normal, successful return value is HeapTupleMayBeUpdated, which
@@ -1274,7 +1274,8 @@ simple_heap_insert(Relation relation, HeapTuple tup)
12741274
*/
12751275
int
12761276
heap_delete(Relationrelation,ItemPointertid,
1277-
ItemPointerctid,CommandIdcid,Snapshotcrosscheck,boolwait)
1277+
ItemPointerctid,CommandIdcid,
1278+
Snapshotcrosscheck,boolwait)
12781279
{
12791280
ItemIdlp;
12801281
HeapTupleDatatp;
@@ -1339,7 +1340,7 @@ heap_delete(Relation relation, ItemPointer tid,
13391340
result=HeapTupleUpdated;
13401341
}
13411342

1342-
if (crosscheck!=SnapshotAny&&result==HeapTupleMayBeUpdated)
1343+
if (crosscheck!=InvalidSnapshot&&result==HeapTupleMayBeUpdated)
13431344
{
13441345
/* Perform additional check for serializable RI updates */
13451346
if (!HeapTupleSatisfiesSnapshot(tp.t_data,crosscheck))
@@ -1443,7 +1444,7 @@ simple_heap_delete(Relation relation, ItemPointer tid)
14431444

14441445
result=heap_delete(relation,tid,
14451446
&ctid,
1446-
GetCurrentCommandId(),SnapshotAny,
1447+
GetCurrentCommandId(),InvalidSnapshot,
14471448
true/* wait for commit */ );
14481449
switch (result)
14491450
{
@@ -1477,7 +1478,7 @@ simple_heap_delete(Relation relation, ItemPointer tid)
14771478
*newtup - newly constructed tuple data to store
14781479
*ctid - output parameter, used only for failure case (see below)
14791480
*cid - update command ID to use in verifying old tuple visibility
1480-
*crosscheck - if notSnapshotAny, also check old tuple against this
1481+
*crosscheck - if notInvalidSnapshot, also check old tuple against this
14811482
*wait - true if should wait for any conflicting update to commit/abort
14821483
*
14831484
* Normal, successful return value is HeapTupleMayBeUpdated, which
@@ -1491,7 +1492,8 @@ simple_heap_delete(Relation relation, ItemPointer tid)
14911492
*/
14921493
int
14931494
heap_update(Relationrelation,ItemPointerotid,HeapTuplenewtup,
1494-
ItemPointerctid,CommandIdcid,Snapshotcrosscheck,boolwait)
1495+
ItemPointerctid,CommandIdcid,
1496+
Snapshotcrosscheck,boolwait)
14951497
{
14961498
ItemIdlp;
14971499
HeapTupleDataoldtup;
@@ -1566,7 +1568,7 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
15661568
result=HeapTupleUpdated;
15671569
}
15681570

1569-
if (crosscheck!=SnapshotAny&&result==HeapTupleMayBeUpdated)
1571+
if (crosscheck!=InvalidSnapshot&&result==HeapTupleMayBeUpdated)
15701572
{
15711573
/* Perform additional check for serializable RI updates */
15721574
if (!HeapTupleSatisfiesSnapshot(oldtup.t_data,crosscheck))
@@ -1804,7 +1806,7 @@ simple_heap_update(Relation relation, ItemPointer otid, HeapTuple tup)
18041806

18051807
result=heap_update(relation,otid,tup,
18061808
&ctid,
1807-
GetCurrentCommandId(),SnapshotAny,
1809+
GetCurrentCommandId(),InvalidSnapshot,
18081810
true/* wait for commit */ );
18091811
switch (result)
18101812
{

‎src/backend/commands/async.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
99
* IDENTIFICATION
10-
* $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.116 2004/09/06 23:32:54 tgl Exp $
10+
* $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.117 2004/09/11 18:28:33 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -544,7 +544,7 @@ AtCommit_Notify(void)
544544
*/
545545
result=heap_update(lRel,&lTuple->t_self,rTuple,
546546
&ctid,
547-
GetCurrentCommandId(),SnapshotAny,
547+
GetCurrentCommandId(),InvalidSnapshot,
548548
false/* no wait for commit */ );
549549
switch (result)
550550
{

‎src/backend/executor/execMain.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -26,7 +26,7 @@
2626
*
2727
*
2828
* IDENTIFICATION
29-
* $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.236 2004/08/29 05:06:42 momjian Exp $
29+
* $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.237 2004/09/11 18:28:34 tgl Exp $
3030
*
3131
*-------------------------------------------------------------------------
3232
*/
@@ -176,7 +176,7 @@ ExecutorStart(QueryDesc *queryDesc, bool useCurrentSnapshot, bool explainOnly)
176176
{
177177
/* normal query --- use query snapshot, no crosscheck */
178178
estate->es_snapshot=CopyQuerySnapshot();
179-
estate->es_crosscheck_snapshot=SnapshotAny;
179+
estate->es_crosscheck_snapshot=InvalidSnapshot;
180180
}
181181

182182
/*

‎src/backend/executor/execUtils.c‎

Lines changed: 2 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/execUtils.c,v 1.114 2004/08/29 05:06:42 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/executor/execUtils.c,v 1.115 2004/09/11 18:28:34 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -179,7 +179,7 @@ CreateExecutorState(void)
179179
*/
180180
estate->es_direction=ForwardScanDirection;
181181
estate->es_snapshot=SnapshotNow;
182-
estate->es_crosscheck_snapshot=SnapshotAny;/* means no crosscheck */
182+
estate->es_crosscheck_snapshot=InvalidSnapshot;/* no crosscheck */
183183
estate->es_range_table=NIL;
184184

185185
estate->es_result_relations=NULL;

‎src/include/utils/tqual.h‎

Lines changed: 21 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
99
* Portions Copyright (c) 1994, Regents of the University of California
1010
*
11-
* $PostgreSQL: pgsql/src/include/utils/tqual.h,v 1.50 2004/08/29 04:13:11 momjian Exp $
11+
* $PostgreSQL: pgsql/src/include/utils/tqual.h,v 1.51 2004/09/11 18:28:34 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -19,6 +19,20 @@
1919
#include"access/xact.h"
2020

2121

22+
/*
23+
* "Regular" snapshots are pointers to a SnapshotData structure.
24+
*
25+
* We also have some "special" snapshot values that have fixed meanings
26+
* and don't need any backing SnapshotData. These are encoded by small
27+
* integer values, which of course is a gross violation of ANSI C, but
28+
* it works fine on all known platforms.
29+
*
30+
* SnapshotDirty is an even more special case: its semantics are fixed,
31+
* but there is a backing SnapshotData struct for it. That struct is
32+
* actually used as *output* data from tqual.c, not input into it.
33+
* (But hey, SnapshotDirty ought to have a dirty implementation, no? ;-))
34+
*/
35+
2236
typedefstructSnapshotData
2337
{
2438
TransactionIdxmin;/* XID < xmin are visible to me */
@@ -32,10 +46,12 @@ typedef struct SnapshotData
3246

3347
typedefSnapshotData*Snapshot;
3448

35-
#defineSnapshotNow((Snapshot) 0x0)
36-
#defineSnapshotSelf((Snapshot) 0x1)
37-
#defineSnapshotAny((Snapshot) 0x2)
38-
#defineSnapshotToast((Snapshot) 0x3)
49+
/* Special snapshot values: */
50+
#defineInvalidSnapshot((Snapshot) 0x0)/* same as NULL */
51+
#defineSnapshotNow((Snapshot) 0x1)
52+
#defineSnapshotSelf((Snapshot) 0x2)
53+
#defineSnapshotAny((Snapshot) 0x3)
54+
#defineSnapshotToast((Snapshot) 0x4)
3955

4056
externDLLIMPORTSnapshotSnapshotDirty;
4157
externDLLIMPORTSnapshotQuerySnapshot;

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