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

@@ -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();