From: Robert Haas <rhaas@postgresql.org>
Date: Thu, 14 Jun 2012 03:26:15 +0000 (-0400)
Subject: Fix page-at-a-time mode to skip the metapage.
X-Git-Url: http://git.postgresql.org/gitweb/static/developers.postgresql.org?a=commitdiff_plain;h=707f8cf1ee5928104e7ee68edf1384d34615239c;p=users%2Frhaas%2Fpostgres.git

Fix page-at-a-time mode to skip the metapage.
---

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 31807d8241..5ff70f2af2 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -216,6 +216,7 @@ heapgetpage(HeapScanDesc scan, BlockNumber page)
 	ItemId		lpp;
 	bool		all_visible;
 
+	Assert(page >= scan->rs_lowpage);
 	Assert(page < scan->rs_nblocks);
 
 	/* release previous scan buffer, if any */
@@ -626,7 +627,7 @@ heapgettup_pagemode(HeapScanDesc scan,
 			/*
 			 * return null immediately if relation is empty
 			 */
-			if (scan->rs_nblocks == 0)
+			if (scan->rs_nblocks == scan->rs_lowpage)
 			{
 				Assert(!BufferIsValid(scan->rs_cbuf));
 				tuple->t_data = NULL;
@@ -657,7 +658,7 @@ heapgettup_pagemode(HeapScanDesc scan,
 			/*
 			 * return null immediately if relation is empty
 			 */
-			if (scan->rs_nblocks == 0)
+			if (scan->rs_nblocks == scan->rs_lowpage)
 			{
 				Assert(!BufferIsValid(scan->rs_cbuf));
 				tuple->t_data = NULL;
@@ -672,7 +673,7 @@ heapgettup_pagemode(HeapScanDesc scan,
 			 */
 			scan->rs_syncscan = false;
 			/* start from last page of the scan */
-			if (scan->rs_startblock > 0)
+			if (scan->rs_startblock > scan->rs_lowpage)
 				page = scan->rs_startblock - 1;
 			else
 				page = scan->rs_nblocks - 1;
@@ -786,7 +787,7 @@ heapgettup_pagemode(HeapScanDesc scan,
 		if (backward)
 		{
 			finished = (page == scan->rs_startblock);
-			if (page == 0)
+			if (page == scan->rs_lowpage)
 				page = scan->rs_nblocks;
 			page--;
 		}
@@ -794,7 +795,7 @@ heapgettup_pagemode(HeapScanDesc scan,
 		{
 			page++;
 			if (page >= scan->rs_nblocks)
-				page = 0;
+				page = scan->rs_lowpage;
 			finished = (page == scan->rs_startblock);
 
 			/*