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.

diff --git a/src/backend/access/hash/hash.c b/src/backend/access/hash/hash.c
index 25e601518a0cdc1a4caf746f0774f1b93403f3db..999d0cfc3184d4b1386ea3a3184ac7a67cd564ea 100644 (file)
--- 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 fec2f5d78a1aa8db8166dfed13be1a6c71110651..eadd45750a7e87009daa77494d0c1dceed71af4f 100644 (file)
--- 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 100ccb9e6dbbc8816814b17d8e22d73f6685b9c9..ce5417044a291ae21f13df022915a8bca35ec4fb 100644 (file)
--- 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;