Add more sanity-checking to PageAddItem and PageIndexTupleDelete,

to prevent spreading of corruption when page header pointers are bad.
Merge PageZero into PageInit, since it was never used separately, and
remove separate memset calls used at most other PageInit call points.
Remove IndexPageCleanup, which wasn't used at all.

src/backend/access/gist/gist.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/gist/gist.c,v 1.86 2001/11/05 17:46:23 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/gist/gist.c,v 1.87 2002/01/15 22:14:16 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1437,7 +1437,7 @@ GISTInitBuffer(Buffer b, uint32 f)
 	pageSize = BufferGetPageSize(b);
 
 	page = BufferGetPage(b);
-	MemSet(page, 0, (int) pageSize);
+
 	PageInit(page, pageSize, sizeof(GISTPageOpaqueData));
 
 	opaque = (GISTPageOpaque) PageGetSpecialPointer(page);

src/backend/access/hash/hashpage.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/hash/hashpage.c,v 1.33 2001/10/25 05:49:21 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/hash/hashpage.c,v 1.34 2002/01/15 22:14:16 tgl Exp $
  *
  * NOTES
  *	  Postgres hash pages look like ordinary relation pages.  The opaque
@@ -301,17 +301,7 @@ _hash_chgbufaccess(Relation rel,
 void
 _hash_pageinit(Page page, Size size)
 {
-	Assert(((PageHeader) page)->pd_lower == 0);
-	Assert(((PageHeader) page)->pd_upper == 0);
-	Assert(((PageHeader) page)->pd_special == 0);
-
-	/*
-	 * Cargo-cult programming -- don't really need this to be zero, but
-	 * creating new pages is an infrequent occurrence and it makes me feel
-	 * good when I know they're empty.
-	 */
-	MemSet(page, 0, size);
-
+	Assert(PageIsNew(page));
 	PageInit(page, size, sizeof(HashPageOpaqueData));
 }
 

src/backend/access/heap/heapam.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/heap/heapam.c,v 1.128 2001/11/05 17:46:23 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/heap/heapam.c,v 1.129 2002/01/15 22:14:17 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -2094,10 +2094,7 @@ heap_xlog_insert(bool redo, XLogRecPtr lsn, XLogRecord *record)
 		uint32		newlen;
 
 		if (record->xl_info & XLOG_HEAP_INIT_PAGE)
-		{
 			PageInit(page, BufferGetPageSize(buffer), 0);
-			PageZero(page);
-		}
 
 		if (XLByteLE(lsn, PageGetLSN(page)))	/* changes are applied */
 		{
@@ -2262,10 +2259,7 @@ newsame:;
 		uint32		newlen;
 
 		if (record->xl_info & XLOG_HEAP_INIT_PAGE)
-		{
 			PageInit(page, BufferGetPageSize(buffer), 0);
-			PageZero(page);
-		}
 
 		if (XLByteLE(lsn, PageGetLSN(page)))	/* changes are applied */
 		{

src/backend/access/nbtree/nbtpage.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtpage.c,v 1.54 2001/10/25 05:49:21 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtpage.c,v 1.55 2002/01/15 22:14:17 tgl Exp $
  *
  *	NOTES
  *	   Postgres btree pages look like ordinary relation pages.	The opaque
@@ -399,14 +399,6 @@ _bt_wrtnorelbuf(Relation rel, Buffer buf)
 void
 _bt_pageinit(Page page, Size size)
 {
-	/*
-	 * Cargo_cult programming -- don't really need this to be zero, but
-	 * creating new pages is an infrequent occurrence and it makes me feel
-	 * good when I know they're empty.
-	 */
-
-	MemSet(page, 0, size);
-
 	PageInit(page, size, sizeof(BTPageOpaqueData));
 	((BTPageOpaque) PageGetSpecialPointer(page))->btpo_parent =
 		InvalidBlockNumber;

src/backend/access/rtree/rtree.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/rtree/Attic/rtree.c,v 1.68 2001/11/05 17:46:24 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/rtree/Attic/rtree.c,v 1.69 2002/01/15 22:14:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1107,7 +1107,7 @@ RTInitBuffer(Buffer b, uint32 f)
 	pageSize = BufferGetPageSize(b);
 
 	page = BufferGetPage(b);
-	MemSet(page, 0, (int) pageSize);
+
 	PageInit(page, pageSize, sizeof(RTreePageOpaqueData));
 
 	opaque = (RTreePageOpaque) PageGetSpecialPointer(page);

src/backend/storage/page/bufpage.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/page/bufpage.c,v 1.41 2001/11/08 04:05:13 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/page/bufpage.c,v 1.42 2002/01/15 22:14:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -20,10 +20,6 @@
 #include "storage/bufpage.h"
 
 
-static void PageIndexTupleDeleteAdjustLinePointers(PageHeader phdr,
-									   char *location, Size size);
-
-
 /* ----------------------------------------------------------------
  *						Page support functions
  * ----------------------------------------------------------------
@@ -44,24 +40,15 @@ PageInit(Page page, Size pageSize, Size specialSize)
 	Assert(pageSize >
 		   specialSize + sizeof(PageHeaderData) - sizeof(ItemIdData));
 
+	/* Make sure all fields of page are zero, as well as unused space */
+	MemSet(p, 0, pageSize);
+
 	p->pd_lower = sizeof(PageHeaderData) - sizeof(ItemIdData);
 	p->pd_upper = pageSize - specialSize;
 	p->pd_special = pageSize - specialSize;
 	PageSetPageSize(page, pageSize);
-
-	p->pd_lsn.xlogid = p->pd_lsn.xrecoff = 0;
-	p->pd_sui = 0;
 }
 
-/*
- * WAL needs in zero-ed page data content
- */
-void
-PageZero(Page page)
-{
-	MemSet((char *) page + ((PageHeader) page)->pd_lower, 0,
-		((PageHeader) page)->pd_special - ((PageHeader) page)->pd_lower);
-}
 
 /* ----------------
  *		PageAddItem
@@ -86,10 +73,11 @@ PageAddItem(Page page,
 			OffsetNumber offsetNumber,
 			ItemIdFlags flags)
 {
+	PageHeader	phdr = (PageHeader) page;
 	int			i;
 	Size		alignedSize;
-	Offset		lower;
-	Offset		upper;
+	int			lower;
+	int			upper;
 	ItemId		itemId;
 	OffsetNumber limit;
 	bool		needshuffle = false;
@@ -97,6 +85,16 @@ PageAddItem(Page page,
 
 	flags &= ~OverwritePageMode;
 
+	/*
+	 * Be wary about corrupted page pointers
+	 */
+	if (phdr->pd_lower < (sizeof(PageHeaderData) - sizeof(ItemIdData)) ||
+		phdr->pd_lower > phdr->pd_upper ||
+		phdr->pd_upper > phdr->pd_special ||
+		phdr->pd_special > BLCKSZ)
+		elog(ERROR, "PageAddItem: corrupted page pointers: lower = %u, upper = %u, special = %u",
+			 phdr->pd_lower, phdr->pd_upper, phdr->pd_special);
+
 	/*
 	 * Find first unallocated offsetNumber
 	 */
@@ -114,7 +112,7 @@ PageAddItem(Page page,
 			}
 			if (offsetNumber < limit)
 			{
-				itemId = &((PageHeader) page)->pd_linp[offsetNumber - 1];
+				itemId = &phdr->pd_linp[offsetNumber - 1];
 				if (((*itemId).lp_flags & LP_USED) ||
 					((*itemId).lp_len != 0))
 				{
@@ -138,7 +136,7 @@ PageAddItem(Page page,
 		/* look for "recyclable" (unused & deallocated) ItemId */
 		for (offsetNumber = 1; offsetNumber < limit; offsetNumber++)
 		{
-			itemId = &((PageHeader) page)->pd_linp[offsetNumber - 1];
+			itemId = &phdr->pd_linp[offsetNumber - 1];
 			if ((((*itemId).lp_flags & LP_USED) == 0) &&
 				((*itemId).lp_len == 0))
 				break;
@@ -146,18 +144,21 @@ PageAddItem(Page page,
 	}
 
 	/*
-	 * Compute new lower and upper pointers for page, see if it'll fit
+	 * Compute new lower and upper pointers for page, see if it'll fit.
+	 *
+	 * Note: do arithmetic as signed ints, to avoid mistakes if, say,
+	 * alignedSize > pd_upper.
 	 */
 	if (offsetNumber > limit)
-		lower = (Offset) (((char *) (&((PageHeader) page)->pd_linp[offsetNumber])) - ((char *) page));
+		lower = (char *) (&phdr->pd_linp[offsetNumber]) - (char *) page;
 	else if (offsetNumber == limit || needshuffle)
-		lower = ((PageHeader) page)->pd_lower + sizeof(ItemIdData);
+		lower = phdr->pd_lower + sizeof(ItemIdData);
 	else
-		lower = ((PageHeader) page)->pd_lower;
+		lower = phdr->pd_lower;
 
 	alignedSize = MAXALIGN(size);
 
-	upper = ((PageHeader) page)->pd_upper - alignedSize;
+	upper = (int) phdr->pd_upper - (int) alignedSize;
 
 	if (lower > upper)
 		return InvalidOffsetNumber;
@@ -169,24 +170,26 @@ PageAddItem(Page page,
 	if (needshuffle)
 	{
 		/* shuffle ItemId's (Do the PageManager Shuffle...) */
-		for (i = (limit - 1); i >= offsetNumber; i--)
+		for (i = (int) limit - 1; i >= (int) offsetNumber; i--)
 		{
 			ItemId		fromitemId,
 						toitemId;
 
-			fromitemId = &((PageHeader) page)->pd_linp[i - 1];
-			toitemId = &((PageHeader) page)->pd_linp[i];
+			fromitemId = &phdr->pd_linp[i - 1];
+			toitemId = &phdr->pd_linp[i];
 			*toitemId = *fromitemId;
 		}
 	}
 
-	itemId = &((PageHeader) page)->pd_linp[offsetNumber - 1];
+	itemId = &phdr->pd_linp[offsetNumber - 1];
 	(*itemId).lp_off = upper;
 	(*itemId).lp_len = size;
 	(*itemId).lp_flags = flags;
+
 	memmove((char *) page + upper, item, size);
-	((PageHeader) page)->pd_lower = lower;
-	((PageHeader) page)->pd_upper = upper;
+
+	phdr->pd_lower = (LocationIndex) lower;
+	phdr->pd_upper = (LocationIndex) upper;
 
 	return offsetNumber;
 }
@@ -383,79 +386,76 @@ PageRepairFragmentation(Page page, OffsetNumber *unused)
 Size
 PageGetFreeSpace(Page page)
 {
-	Size		space;
+	int			space;
 
-	space = ((PageHeader) page)->pd_upper - ((PageHeader) page)->pd_lower;
+	/*
+	 * Use signed arithmetic here so that we behave sensibly if
+	 * pd_lower > pd_upper.
+	 */
+	space = (int) ((PageHeader) page)->pd_upper -
+		(int) ((PageHeader) page)->pd_lower;
 
-	if (space < sizeof(ItemIdData))
+	if (space < (int) sizeof(ItemIdData))
 		return 0;
 	space -= sizeof(ItemIdData);	/* XXX not always appropriate */
 
-	return space;
+	return (Size) space;
 }
 
-/*
- * PageRepairFragmentation un-useful for index page cleanup because
- * of it doesn't remove line pointers. This routine could be more
- * effective but ... no time -:)
- */
-void
-IndexPageCleanup(Buffer buffer)
-{
-	Page		page = (Page) BufferGetPage(buffer);
-	ItemId		lp;
-	OffsetNumber maxoff;
-	OffsetNumber i;
-
-	maxoff = PageGetMaxOffsetNumber(page);
-	for (i = 0; i < maxoff; i++)
-	{
-		lp = ((PageHeader) page)->pd_linp + i;
-		if ((*lp).lp_flags & LP_DELETE) /* marked for deletion */
-		{
-			PageIndexTupleDelete(page, i + 1);
-			maxoff--;
-		}
-	}
-}
 
 /*
- *----------------------------------------------------------------
  * PageIndexTupleDelete
- *----------------------------------------------------------------
  *
- *		This routine does the work of removing a tuple from an index page.
+ * This routine does the work of removing a tuple from an index page.
+ *
+ * Unlike heap pages, we compact out the line pointer for the removed tuple.
  */
 void
 PageIndexTupleDelete(Page page, OffsetNumber offnum)
 {
-	PageHeader	phdr;
+	PageHeader	phdr = (PageHeader) page;
 	char	   *addr;
 	ItemId		tup;
 	Size		size;
-	char	   *locn;
+	unsigned	offset;
 	int			nbytes;
 	int			offidx;
+	int			nline,
+				i;
+
+	/*
+	 * As with PageRepairFragmentation, paranoia seems justified.
+	 */
+	if (phdr->pd_lower < (sizeof(PageHeaderData) - sizeof(ItemIdData)) ||
+		phdr->pd_lower > phdr->pd_upper ||
+		phdr->pd_upper > phdr->pd_special ||
+		phdr->pd_special > BLCKSZ)
+		elog(ERROR, "PageIndexTupleDelete: corrupted page pointers: lower = %u, upper = %u, special = %u",
+			 phdr->pd_lower, phdr->pd_upper, phdr->pd_special);
 
-	phdr = (PageHeader) page;
+	nline = PageGetMaxOffsetNumber(page);
+	if ((int) offnum <= 0 || (int) offnum > nline)
+		elog(ERROR, "PageIndexTupleDelete: bad offnum %u", offnum);
 
 	/* change offset number to offset index */
 	offidx = offnum - 1;
 
 	tup = PageGetItemId(page, offnum);
 	size = ItemIdGetLength(tup);
-	size = MAXALIGN(size);
+	offset = ItemIdGetOffset(tup);
 
-	/* location of deleted tuple data */
-	locn = (char *) (page + ItemIdGetOffset(tup));
+	if (offset < phdr->pd_upper || (offset + size) > phdr->pd_special ||
+		offset != MAXALIGN(offset) || size != MAXALIGN(size))
+		elog(ERROR, "PageIndexTupleDelete: corrupted item pointer: offset = %u size = %u",
+			 offset, size);
 
 	/*
 	 * First, we want to get rid of the pd_linp entry for the index tuple.
 	 * We copy all subsequent linp's back one slot in the array.
 	 */
-
 	nbytes = phdr->pd_lower -
 		((char *) &phdr->pd_linp[offidx + 1] - (char *) phdr);
+
 	memmove((char *) &(phdr->pd_linp[offidx]),
 			(char *) &(phdr->pd_linp[offidx + 1]),
 			nbytes);
@@ -470,52 +470,28 @@ PageIndexTupleDelete(Page page, OffsetNumber offnum)
 	 */
 
 	/* beginning of tuple space */
-	addr = (char *) (page + phdr->pd_upper);
+	addr = (char *) page + phdr->pd_upper;
 
-	if (locn != addr)
-		memmove(addr + size, addr, (int) (locn - addr));
+	if (offset > phdr->pd_upper)
+		memmove(addr + size, addr, (int) (offset - phdr->pd_upper));
 
 	/* adjust free space boundary pointers */
 	phdr->pd_upper += size;
 	phdr->pd_lower -= sizeof(ItemIdData);
 
-	/* finally, we need to adjust the linp entries that remain */
+	/*
+	 * Finally, we need to adjust the linp entries that remain.
+	 *
+	 * Anything that used to be before the deleted tuple's data was moved
+	 * forward by the size of the deleted tuple.
+	 */
 	if (!PageIsEmpty(page))
-		PageIndexTupleDeleteAdjustLinePointers(phdr, locn, size);
-}
-
-/*
- *----------------------------------------------------------------
- * PageIndexTupleDeleteAdjustLinePointers
- *----------------------------------------------------------------
- *
- *		Once the line pointers and tuple data have been shifted around
- *		on the page, we need to go down the line pointer vector and
- *		adjust pointers to reflect new locations.  Anything that used
- *		to be before the deleted tuple's data was moved forward by the
- *		size of the deleted tuple.
- *
- *		This routine does the work of adjusting the line pointers.
- *		Location is where the tuple data used to lie; size is how
- *		much space it occupied.  We assume that size has been aligned
- *		as required by the time we get here.
- *
- *		This routine should never be called on an empty page.
- */
-static void
-PageIndexTupleDeleteAdjustLinePointers(PageHeader phdr,
-									   char *location,
-									   Size size)
-{
-	int			i;
-	unsigned	offset;
-
-	/* location is an index into the page... */
-	offset = (unsigned) (location - (char *) phdr);
-
-	for (i = PageGetMaxOffsetNumber((Page) phdr) - 1; i >= 0; i--)
 	{
-		if (phdr->pd_linp[i].lp_off <= offset)
-			phdr->pd_linp[i].lp_off += size;
+		nline--;				/* there's one less than when we started */
+		for (i = nline; --i >= 0; )
+		{
+			if (phdr->pd_linp[i].lp_off <= offset)
+				phdr->pd_linp[i].lp_off += size;
+		}
 	}
 }

src/include/storage/bufpage.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: bufpage.h,v 1.46 2001/11/05 17:46:35 momjian Exp $
+ * $Id: bufpage.h,v 1.47 2002/01/15 22:14:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -310,7 +310,6 @@ typedef enum
  */
 
 extern void PageInit(Page page, Size pageSize, Size specialSize);
-extern void PageZero(Page page);
 extern OffsetNumber PageAddItem(Page page, Item item, Size size,
 			OffsetNumber offsetNumber, ItemIdFlags flags);
 extern Page PageGetTempPage(Page page, Size specialSize);
@@ -318,6 +317,5 @@ extern void PageRestoreTempPage(Page tempPage, Page oldPage);
 extern int	PageRepairFragmentation(Page page, OffsetNumber *unused);
 extern Size PageGetFreeSpace(Page page);
 extern void PageIndexTupleDelete(Page page, OffsetNumber offset);
-extern void IndexPageCleanup(Buffer buffer);
 
 #endif   /* BUFPAGE_H */