Fix possible duplicate tuples while GiST scan. Now page is processed

at once and ItemPointers are collected in memory.

Remove tuple's killing by killtuple() if tuple was moved to another
page - it could produce unaceptable overhead.

Backpatch up to 8.1 because the bug was introduced by GiST's concurrency support.

1 files changed, 14 insertions, 1 deletions

diff --git a/src/backend/access/gist/gistscan.c b/src/backend/access/gist/gistscan.c
index b0fdb740047..4864fd1248d 100644
--- a/src/backend/access/gist/gistscan.c
+++ b/src/backend/access/gist/gistscan.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/gist/gistscan.c,v 1.65 2006/10/04 00:29:48 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/gist/gistscan.c,v 1.65.2.1 2008/08/23 10:41:38 teodor Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -67,6 +67,7 @@ gistrescan(PG_FUNCTION_ARGS)
 			ReleaseBuffer(so->markbuf);
 			so->markbuf = InvalidBuffer;
 		}
+
 	}
 	else
 	{
@@ -82,6 +83,8 @@ gistrescan(PG_FUNCTION_ARGS)
 		scan->opaque = so;
 	}
 
+	so->nPageData = so->curPageData = 0;
+
 	/* Update scan key, if a new one is given */
 	if (key && scan->numberOfKeys > 0)
 	{
@@ -148,6 +151,11 @@ gistmarkpos(PG_FUNCTION_ARGS)
 		so->markbuf = so->curbuf;
 	}
 
+	so->markNPageData = so->nPageData;
+	so->markCurPageData = so->curPageData;
+	if ( so->markNPageData > 0 )
+		memcpy( so->markPageData, so->pageData, sizeof(ItemPointerData) * so->markNPageData );		
+
 	PG_RETURN_VOID();
 }
 
@@ -197,6 +205,11 @@ gistrestrpos(PG_FUNCTION_ARGS)
 		so->curbuf = so->markbuf;
 	}
 
+	so->nPageData = so->markNPageData;
+	so->curPageData = so->markNPageData;
+	if ( so->markNPageData > 0 )
+		memcpy( so->pageData, so->markPageData, sizeof(ItemPointerData) * so->markNPageData );		
+
 	PG_RETURN_VOID();
 }