From ef148d6b8592e19cfeb9e2bee4255ddadc2ae3dd Mon Sep 17 00:00:00 2001
From: Teodor Sigaev <teodor@sigaev.ru>
Date: Thu, 30 Nov 2006 16:22:32 +0000
Subject: [PATCH] Fix bug with page deletion. If inner page is removed and it
 tries to remove page on next level linked from next inner page,
 ginScanToDelete() wrongly sets parent page. Bug reveals when many item
 pointers from index was deleted ( several hundred thousands).

Bug is discovered by hubert depesz lubaczewski <depesz@gmail.com>

Suppose, we need rc2 before release...
---
 src/backend/access/gin/ginvacuum.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/src/backend/access/gin/ginvacuum.c b/src/backend/access/gin/ginvacuum.c
index c3415ffe44..225dbc6047 100644
--- a/src/backend/access/gin/ginvacuum.c
+++ b/src/backend/access/gin/ginvacuum.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *			$PostgreSQL: pgsql/src/backend/access/gin/ginvacuum.c,v 1.8 2006/11/12 06:55:53 neilc Exp $
+ *			$PostgreSQL: pgsql/src/backend/access/gin/ginvacuum.c,v 1.9 2006/11/30 16:22:32 teodor Exp $
  *-------------------------------------------------------------------------
  */
 
@@ -265,6 +265,12 @@ ginDeletePage(GinVacuumState *gvs, BlockNumber deleteBlkno, BlockNumber leftBlkn
 	}
 
 	parentPage = BufferGetPage(pBuffer);
+#ifdef USE_ASSERT_CHECKING
+	do {
+		PostingItem *tod=(PostingItem *) GinDataPageGetItem(parentPage, myoff);
+		Assert( PostingItemGetBlockNumber(tod) == deleteBlkno );
+	} while(0);
+#endif
 	PageDeletePostingItem(parentPage, myoff);
 
 	page = BufferGetPage(dBuffer);
@@ -351,7 +357,8 @@ typedef struct DataPageDeleteStack
 	struct DataPageDeleteStack *child;
 	struct DataPageDeleteStack *parent;
 
-	BlockNumber blkno;
+	BlockNumber blkno; /* current block number */
+	BlockNumber leftBlkno; /* rightest non-deleted page on left */
 	bool		isRoot;
 } DataPageDeleteStack;
 
@@ -377,7 +384,7 @@ ginScanToDelete(GinVacuumState *gvs, BlockNumber blkno, bool isRoot, DataPageDel
 			me = (DataPageDeleteStack *) palloc0(sizeof(DataPageDeleteStack));
 			me->parent = parent;
 			parent->child = me;
-			me->blkno = InvalidBlockNumber;
+			me->leftBlkno = InvalidBlockNumber;
 		}
 		else
 			me = parent->child;
@@ -392,6 +399,7 @@ ginScanToDelete(GinVacuumState *gvs, BlockNumber blkno, bool isRoot, DataPageDel
 	{
 		OffsetNumber i;
 
+		me->blkno = blkno;
 		for (i = FirstOffsetNumber; i <= GinPageGetOpaque(page)->maxoff; i++)
 		{
 			PostingItem *pitem = (PostingItem *) GinDataPageGetItem(page, i);
@@ -403,13 +411,13 @@ ginScanToDelete(GinVacuumState *gvs, BlockNumber blkno, bool isRoot, DataPageDel
 
 	if (GinPageGetOpaque(page)->maxoff < FirstOffsetNumber)
 	{
-		if (!(me->blkno == InvalidBlockNumber && GinPageRightMost(page)))
+		if (!(me->leftBlkno == InvalidBlockNumber && GinPageRightMost(page)))
 		{
 			/* we never delete right most branch */
 			Assert(!isRoot);
 			if (GinPageGetOpaque(page)->maxoff < FirstOffsetNumber)
 			{
-				ginDeletePage(gvs, blkno, me->blkno, me->parent->blkno, myoff, me->parent->isRoot);
+				ginDeletePage(gvs, blkno, me->leftBlkno, me->parent->blkno, myoff, me->parent->isRoot);
 				meDelete = TRUE;
 			}
 		}
@@ -418,7 +426,7 @@ ginScanToDelete(GinVacuumState *gvs, BlockNumber blkno, bool isRoot, DataPageDel
 	ReleaseBuffer(buffer);
 
 	if (!meDelete)
-		me->blkno = blkno;
+		me->leftBlkno = blkno;
 
 	return meDelete;
 }
@@ -438,7 +446,7 @@ ginVacuumPostingTree(GinVacuumState *gvs, BlockNumber rootBlkno)
 	}
 
 	memset(&root, 0, sizeof(DataPageDeleteStack));
-	root.blkno = rootBlkno;
+	root.leftBlkno = InvalidBlockNumber;
 	root.isRoot = TRUE;
 
 	vacuum_delay_point();
-- 
2.40.0