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Commit7d535eb

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Dept of second thoughts: after studying index_getnext() a bit more I realize
that it can scribble on scan->xs_ctup.t_self while following HOT chains,so we can't rely on that to stay valid between hashgettuple() calls.Introduce a private variable in HashScanOpaque, instead.
1 parentc4afdca commit7d535eb

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3 files changed

+16
-8
lines changed

3 files changed

+16
-8
lines changed

‎src/backend/access/hash/hash.c

Lines changed: 8 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.114 2009/11/0121:25:25 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.115 2009/11/0122:30:54 tgl Exp $
1212
*
1313
* NOTES
1414
* This file contains only the public interface routines.
@@ -251,7 +251,7 @@ hashgettuple(PG_FUNCTION_ARGS)
251251
IndexTupleitup;
252252

253253
itup= (IndexTuple)PageGetItem(page,PageGetItemId(page,offnum));
254-
if (ItemPointerEquals(&scan->xs_ctup.t_self,&itup->t_tid))
254+
if (ItemPointerEquals(&(so->hashso_heappos),&(itup->t_tid)))
255255
break;
256256
}
257257
if (offnum>maxoffnum)
@@ -304,6 +304,9 @@ hashgettuple(PG_FUNCTION_ARGS)
304304
if (BufferIsValid(so->hashso_curbuf))
305305
_hash_chgbufaccess(rel,so->hashso_curbuf,HASH_READ,HASH_NOLOCK);
306306

307+
/* Return current heap TID on success */
308+
scan->xs_ctup.t_self=so->hashso_heappos;
309+
307310
PG_RETURN_BOOL(res);
308311
}
309312

@@ -345,7 +348,7 @@ hashgetbitmap(PG_FUNCTION_ARGS)
345348
if (add_tuple)
346349
{
347350
/* Note we mark the tuple ID as requiring recheck */
348-
tbm_add_tuples(tbm,&scan->xs_ctup.t_self,1, true);
351+
tbm_add_tuples(tbm,&(so->hashso_heappos),1, true);
349352
ntids++;
350353
}
351354

@@ -375,6 +378,7 @@ hashbeginscan(PG_FUNCTION_ARGS)
375378
so->hashso_curbuf=InvalidBuffer;
376379
/* set position invalid (this will cause _hash_first call) */
377380
ItemPointerSetInvalid(&(so->hashso_curpos));
381+
ItemPointerSetInvalid(&(so->hashso_heappos));
378382

379383
scan->opaque=so;
380384

@@ -410,6 +414,7 @@ hashrescan(PG_FUNCTION_ARGS)
410414

411415
/* set position invalid (this will cause _hash_first call) */
412416
ItemPointerSetInvalid(&(so->hashso_curpos));
417+
ItemPointerSetInvalid(&(so->hashso_heappos));
413418
}
414419

415420
/* Update scan key, if a new one is given */

‎src/backend/access/hash/hashsearch.c

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/access/hash/hashsearch.c,v 1.57 2009/06/11 14:48:53 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/hash/hashsearch.c,v 1.58 2009/11/01 22:30:54 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -58,7 +58,7 @@ _hash_next(IndexScanDesc scan, ScanDirection dir)
5858
_hash_checkpage(rel,buf,LH_BUCKET_PAGE |LH_OVERFLOW_PAGE);
5959
page=BufferGetPage(buf);
6060
itup= (IndexTuple)PageGetItem(page,PageGetItemId(page,offnum));
61-
scan->xs_ctup.t_self=itup->t_tid;
61+
so->hashso_heappos=itup->t_tid;
6262

6363
return true;
6464
}
@@ -242,7 +242,7 @@ _hash_first(IndexScanDesc scan, ScanDirection dir)
242242
_hash_checkpage(rel,buf,LH_BUCKET_PAGE |LH_OVERFLOW_PAGE);
243243
page=BufferGetPage(buf);
244244
itup= (IndexTuple)PageGetItem(page,PageGetItemId(page,offnum));
245-
scan->xs_ctup.t_self=itup->t_tid;
245+
so->hashso_heappos=itup->t_tid;
246246

247247
return true;
248248
}

‎src/include/access/hash.h

Lines changed: 5 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/access/hash.h,v 1.94 2009/11/0121:25:25 tgl Exp $
10+
* $PostgreSQL: pgsql/src/include/access/hash.h,v 1.95 2009/11/0122:30:54 tgl Exp $
1111
*
1212
* NOTES
1313
*modeled after Margo Seltzer's hash implementation for unix.
@@ -99,8 +99,11 @@ typedef struct HashScanOpaqueData
9999
*/
100100
Bufferhashso_curbuf;
101101

102-
/* Current position of the scan */
102+
/* Current position of the scan, as an index TID */
103103
ItemPointerDatahashso_curpos;
104+
105+
/* Current position of the scan, as a heap TID */
106+
ItemPointerDatahashso_heappos;
104107
}HashScanOpaqueData;
105108

106109
typedefHashScanOpaqueData*HashScanOpaque;

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