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Dept of second thoughts: after studying index_getnext() a bit more I realize

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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.
This commit is contained in:
Tom Lane 2009-11-01 22:30:54 +00:00
parent c4afdca4c2
commit 7d535ebe5b
3 changed files with 16 additions and 8 deletions
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11
src/backend/access/hash/hash.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.114 2009/11/01 21:25:25 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.115 2009/11/01 22:30:54 tgl Exp $
*
* NOTES
* This file contains only the public interface routines.
@ -251,7 +251,7 @@ hashgettuple(PG_FUNCTION_ARGS)
IndexTuple itup;
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
if (ItemPointerEquals(&scan->xs_ctup.t_self, &itup->t_tid))
if (ItemPointerEquals(&(so->hashso_heappos), &(itup->t_tid)))
break;
}
if (offnum > maxoffnum)
@ -304,6 +304,9 @@ hashgettuple(PG_FUNCTION_ARGS)
if (BufferIsValid(so->hashso_curbuf))
_hash_chgbufaccess(rel, so->hashso_curbuf, HASH_READ, HASH_NOLOCK);
/* Return current heap TID on success */
scan->xs_ctup.t_self = so->hashso_heappos;
PG_RETURN_BOOL(res);
}
@ -345,7 +348,7 @@ hashgetbitmap(PG_FUNCTION_ARGS)
if (add_tuple)
{
/* Note we mark the tuple ID as requiring recheck */
tbm_add_tuples(tbm, &scan->xs_ctup.t_self, 1, true);
tbm_add_tuples(tbm, &(so->hashso_heappos), 1, true);
ntids++;
}
@ -375,6 +378,7 @@ hashbeginscan(PG_FUNCTION_ARGS)
so->hashso_curbuf = InvalidBuffer;
/* set position invalid (this will cause _hash_first call) */
ItemPointerSetInvalid(&(so->hashso_curpos));
ItemPointerSetInvalid(&(so->hashso_heappos));
scan->opaque = so;
@ -410,6 +414,7 @@ hashrescan(PG_FUNCTION_ARGS)
/* set position invalid (this will cause _hash_first call) */
ItemPointerSetInvalid(&(so->hashso_curpos));
ItemPointerSetInvalid(&(so->hashso_heappos));
}
/* Update scan key, if a new one is given */

6
src/backend/access/hash/hashsearch.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/hash/hashsearch.c,v 1.57 2009/06/11 14:48:53 momjian Exp $
* $PostgreSQL: pgsql/src/backend/access/hash/hashsearch.c,v 1.58 2009/11/01 22:30:54 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -58,7 +58,7 @@ _hash_next(IndexScanDesc scan, ScanDirection dir)
_hash_checkpage(rel, buf, LH_BUCKET_PAGE | LH_OVERFLOW_PAGE);
page = BufferGetPage(buf);
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
scan->xs_ctup.t_self = itup->t_tid;
so->hashso_heappos = itup->t_tid;
return true;
}
@ -242,7 +242,7 @@ _hash_first(IndexScanDesc scan, ScanDirection dir)
_hash_checkpage(rel, buf, LH_BUCKET_PAGE | LH_OVERFLOW_PAGE);
page = BufferGetPage(buf);
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
scan->xs_ctup.t_self = itup->t_tid;
so->hashso_heappos = itup->t_tid;
return true;
}

7
src/include/access/hash.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/hash.h,v 1.94 2009/11/01 21:25:25 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/hash.h,v 1.95 2009/11/01 22:30:54 tgl Exp $
*
* NOTES
* modeled after Margo Seltzer's hash implementation for unix.
@ -99,8 +99,11 @@ typedef struct HashScanOpaqueData
*/
Buffer hashso_curbuf;
/* Current position of the scan */
/* Current position of the scan, as an index TID */
ItemPointerData hashso_curpos;
/* Current position of the scan, as a heap TID */
ItemPointerData hashso_heappos;
} HashScanOpaqueData;
typedef HashScanOpaqueData *HashScanOpaque;