From 7d535ebe5bf95ca88891c0288fa1c6575498185e Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 1 Nov 2009 22:30:54 +0000
Subject: [PATCH] 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.
---
src/backend/access/hash/hash.c | 11 ++++++++---
src/backend/access/hash/hashsearch.c | 6 +++---
src/include/access/hash.h | 7 +++++--
3 files changed, 16 insertions(+), 8 deletions(-)
diff --git a/src/backend/access/hash/hash.c b/src/backend/access/hash/hash.c
index 25e601518a0..999d0cfc318 100644
--- a/src/backend/access/hash/hash.c
+++ b/src/backend/access/hash/hash.c
@@ -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 */
diff --git a/src/backend/access/hash/hashsearch.c b/src/backend/access/hash/hashsearch.c
index fec2f5d78a1..eadd45750a7 100644
--- a/src/backend/access/hash/hashsearch.c
+++ b/src/backend/access/hash/hashsearch.c
@@ -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;
}
diff --git a/src/include/access/hash.h b/src/include/access/hash.h
index 100ccb9e6db..ce5417044a2 100644
--- a/src/include/access/hash.h
+++ b/src/include/access/hash.h
@@ -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;
--
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