Clean up the use of some page-header-access macros: principally, use

SizeOfPageHeaderData instead of sizeof(PageHeaderData) in places where that
makes the code clearer, and avoid casting between Page and PageHeader where
possible.  Zdenek Kotala, with some additional cleanup by Heikki Linnakangas.

I did not apply the parts of the proposed patch that would have resulted in
slightly changing the on-disk format of hash indexes; it seems to me that's
not a win as long as there's any chance of having in-place upgrade for 8.4.

Author: tglsfdc

src/backend/access/gist/gistutil.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *			$PostgreSQL: pgsql/src/backend/access/gist/gistutil.c,v 1.29 2008/06/19 00:46:03 alvherre Exp $
+ *			$PostgreSQL: pgsql/src/backend/access/gist/gistutil.c,v 1.30 2008/07/13 20:45:46 tgl Exp $
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
@@ -591,8 +591,7 @@ gistcheckpage(Relation rel, Buffer buf)
 	/*
 	 * Additionally check that the special area looks sane.
 	 */
-	if (((PageHeader) (page))->pd_special !=
-		(BLCKSZ - MAXALIGN(sizeof(GISTPageOpaqueData))))
+	if (PageGetSpecialSize(page) != MAXALIGN(sizeof(GISTPageOpaqueData)))
 		ereport(ERROR,
 				(errcode(ERRCODE_INDEX_CORRUPTED),
 				 errmsg("index \"%s\" contains corrupted page at block %u",

src/backend/access/hash/hashutil.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/hash/hashutil.c,v 1.55 2008/06/19 00:46:03 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/hash/hashutil.c,v 1.56 2008/07/13 20:45:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -164,8 +164,7 @@ _hash_checkpage(Relation rel, Buffer buf, int flags)
 	/*
 	 * Additionally check that the special area looks sane.
 	 */
-	if (((PageHeader) (page))->pd_special !=
-		(BLCKSZ - MAXALIGN(sizeof(HashPageOpaqueData))))
+	if (PageGetSpecialSize(page) != MAXALIGN(sizeof(HashPageOpaqueData)))
 		ereport(ERROR,
 				(errcode(ERRCODE_INDEX_CORRUPTED),
 				 errmsg("index \"%s\" contains corrupted page at block %u",

src/backend/access/heap/heapam.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.260 2008/06/19 00:46:03 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.261 2008/07/13 20:45:47 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -1343,7 +1343,7 @@ heap_fetch(Relation relation,
 	ItemPointer tid = &(tuple->t_self);
 	ItemId		lp;
 	Buffer		buffer;
-	PageHeader	dp;
+	Page		page;
 	OffsetNumber offnum;
 	bool		valid;
 
@@ -1356,14 +1356,14 @@ heap_fetch(Relation relation,
 	 * Need share lock on buffer to examine tuple commit status.
 	 */
 	LockBuffer(buffer, BUFFER_LOCK_SHARE);
-	dp = (PageHeader) BufferGetPage(buffer);
+	page = BufferGetPage(buffer);
 
 	/*
 	 * We'd better check for out-of-range offnum in case of VACUUM since the
 	 * TID was obtained.
 	 */
 	offnum = ItemPointerGetOffsetNumber(tid);
-	if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(dp))
+	if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(page))
 	{
 		LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
 		if (keep_buf)
@@ -1380,7 +1380,7 @@ heap_fetch(Relation relation,
 	/*
 	 * get the item line pointer corresponding to the requested tid
 	 */
-	lp = PageGetItemId(dp, offnum);
+	lp = PageGetItemId(page, offnum);
 
 	/*
 	 * Must check for deleted tuple.
@@ -1402,7 +1402,7 @@ heap_fetch(Relation relation,
 	/*
 	 * fill in *tuple fields
 	 */
-	tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
+	tuple->t_data = (HeapTupleHeader) PageGetItem(page, lp);
 	tuple->t_len = ItemIdGetLength(lp);
 	tuple->t_tableOid = RelationGetRelid(relation);
 
@@ -1627,7 +1627,7 @@ heap_get_latest_tid(Relation relation,
 	for (;;)
 	{
 		Buffer		buffer;
-		PageHeader	dp;
+		Page		page;
 		OffsetNumber offnum;
 		ItemId		lp;
 		HeapTupleData tp;
@@ -1638,20 +1638,20 @@ heap_get_latest_tid(Relation relation,
 		 */
 		buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(&ctid));
 		LockBuffer(buffer, BUFFER_LOCK_SHARE);
-		dp = (PageHeader) BufferGetPage(buffer);
+		page = BufferGetPage(buffer);
 
 		/*
 		 * Check for bogus item number.  This is not treated as an error
 		 * condition because it can happen while following a t_ctid link. We
 		 * just assume that the prior tid is OK and return it unchanged.
 		 */
 		offnum = ItemPointerGetOffsetNumber(&ctid);
-		if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(dp))
+		if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(page))
 		{
 			UnlockReleaseBuffer(buffer);
 			break;
 		}
-		lp = PageGetItemId(dp, offnum);
+		lp = PageGetItemId(page, offnum);
 		if (!ItemIdIsNormal(lp))
 		{
 			UnlockReleaseBuffer(buffer);
@@ -1660,7 +1660,7 @@ heap_get_latest_tid(Relation relation,
 
 		/* OK to access the tuple */
 		tp.t_self = ctid;
-		tp.t_data = (HeapTupleHeader) PageGetItem(dp, lp);
+		tp.t_data = (HeapTupleHeader) PageGetItem(page, lp);
 		tp.t_len = ItemIdGetLength(lp);
 
 		/*
@@ -1964,7 +1964,7 @@ heap_delete(Relation relation, ItemPointer tid,
 	TransactionId xid = GetCurrentTransactionId();
 	ItemId		lp;
 	HeapTupleData tp;
-	PageHeader	dp;
+	Page		page;
 	Buffer		buffer;
 	bool		have_tuple_lock = false;
 	bool		iscombo;
@@ -1974,11 +1974,11 @@ heap_delete(Relation relation, ItemPointer tid,
 	buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid));
 	LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
 
-	dp = (PageHeader) BufferGetPage(buffer);
-	lp = PageGetItemId(dp, ItemPointerGetOffsetNumber(tid));
+	page = BufferGetPage(buffer);
+	lp = PageGetItemId(page, ItemPointerGetOffsetNumber(tid));
 	Assert(ItemIdIsNormal(lp));
 
-	tp.t_data = (HeapTupleHeader) PageGetItem(dp, lp);
+	tp.t_data = (HeapTupleHeader) PageGetItem(page, lp);
 	tp.t_len = ItemIdGetLength(lp);
 	tp.t_self = *tid;
 
@@ -2112,7 +2112,7 @@ heap_delete(Relation relation, ItemPointer tid,
 	 * the subsequent page pruning will be a no-op and the hint will be
 	 * cleared.
 	 */
-	PageSetPrunable(dp, xid);
+	PageSetPrunable(page, xid);
 
 	/* store transaction information of xact deleting the tuple */
 	tp.t_data->t_infomask &= ~(HEAP_XMAX_COMMITTED |
@@ -2150,8 +2150,8 @@ heap_delete(Relation relation, ItemPointer tid,
 
 		recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_DELETE, rdata);
 
-		PageSetLSN(dp, recptr);
-		PageSetTLI(dp, ThisTimeLineID);
+		PageSetLSN(page, recptr);
+		PageSetTLI(page, ThisTimeLineID);
 	}
 
 	END_CRIT_SECTION();
@@ -2276,7 +2276,7 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
 	ItemId		lp;
 	HeapTupleData oldtup;
 	HeapTuple	heaptup;
-	PageHeader	dp;
+	Page		page;
 	Buffer		buffer,
 				newbuf;
 	bool		need_toast,
@@ -2306,11 +2306,11 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
 	buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(otid));
 	LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
 
-	dp = (PageHeader) BufferGetPage(buffer);
-	lp = PageGetItemId(dp, ItemPointerGetOffsetNumber(otid));
+	page = BufferGetPage(buffer);
+	lp = PageGetItemId(page, ItemPointerGetOffsetNumber(otid));
 	Assert(ItemIdIsNormal(lp));
 
-	oldtup.t_data = (HeapTupleHeader) PageGetItem(dp, lp);
+	oldtup.t_data = (HeapTupleHeader) PageGetItem(page, lp);
 	oldtup.t_len = ItemIdGetLength(lp);
 	oldtup.t_self = *otid;
 
@@ -2491,7 +2491,7 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
 					  HeapTupleHasExternal(newtup) ||
 					  newtup->t_len > TOAST_TUPLE_THRESHOLD);
 
-	pagefree = PageGetHeapFreeSpace((Page) dp);
+	pagefree = PageGetHeapFreeSpace(page);
 
 	newtupsize = MAXALIGN(newtup->t_len);
 
@@ -2557,7 +2557,7 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
 			/* Re-acquire the lock on the old tuple's page. */
 			LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
 			/* Re-check using the up-to-date free space */
-			pagefree = PageGetHeapFreeSpace((Page) dp);
+			pagefree = PageGetHeapFreeSpace(page);
 			if (newtupsize > pagefree)
 			{
 				/*
@@ -2603,7 +2603,7 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
 	else
 	{
 		/* Set a hint that the old page could use prune/defrag */
-		PageSetFull(dp);
+		PageSetFull(page);
 	}
 
 	/* NO EREPORT(ERROR) from here till changes are logged */
@@ -2621,7 +2621,7 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
 	 * not to optimize for aborts.	Note that heap_xlog_update must be kept in
 	 * sync if this decision changes.
 	 */
-	PageSetPrunable(dp, xid);
+	PageSetPrunable(page, xid);
 
 	if (use_hot_update)
 	{
@@ -2946,7 +2946,7 @@ heap_lock_tuple(Relation relation, HeapTuple tuple, Buffer *buffer,
 	HTSU_Result result;
 	ItemPointer tid = &(tuple->t_self);
 	ItemId		lp;
-	PageHeader	dp;
+	Page		page;
 	TransactionId xid;
 	TransactionId xmax;
 	uint16		old_infomask;
@@ -2959,11 +2959,11 @@ heap_lock_tuple(Relation relation, HeapTuple tuple, Buffer *buffer,
 	*buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid));
 	LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
 
-	dp = (PageHeader) BufferGetPage(*buffer);
-	lp = PageGetItemId(dp, ItemPointerGetOffsetNumber(tid));
+	page = BufferGetPage(*buffer);
+	lp = PageGetItemId(page, ItemPointerGetOffsetNumber(tid));
 	Assert(ItemIdIsNormal(lp));
 
-	tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
+	tuple->t_data = (HeapTupleHeader) PageGetItem(page, lp);
 	tuple->t_len = ItemIdGetLength(lp);
 	tuple->t_tableOid = RelationGetRelid(relation);
 
@@ -3302,8 +3302,8 @@ heap_lock_tuple(Relation relation, HeapTuple tuple, Buffer *buffer,
 
 		recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_LOCK, rdata);
 
-		PageSetLSN(dp, recptr);
-		PageSetTLI(dp, ThisTimeLineID);
+		PageSetLSN(page, recptr);
+		PageSetTLI(page, ThisTimeLineID);
 	}
 
 	END_CRIT_SECTION();

src/backend/access/heap/hio.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/heap/hio.c,v 1.71 2008/06/08 22:00:47 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/heap/hio.c,v 1.72 2008/07/13 20:45:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -107,7 +107,7 @@ RelationGetBufferForTuple(Relation relation, Size len,
 						  Buffer otherBuffer, bool use_fsm)
 {
 	Buffer		buffer = InvalidBuffer;
-	Page		pageHeader;
+	Page		page;
 	Size		pageFreeSpace,
 				saveFreeSpace;
 	BlockNumber targetBlock,
@@ -218,8 +218,8 @@ RelationGetBufferForTuple(Relation relation, Size len,
 		 * Now we can check to see if there's enough free space here. If so,
 		 * we're done.
 		 */
-		pageHeader = (Page) BufferGetPage(buffer);
-		pageFreeSpace = PageGetHeapFreeSpace(pageHeader);
+		page = BufferGetPage(buffer);
+		pageFreeSpace = PageGetHeapFreeSpace(page);
 		if (len + saveFreeSpace <= pageFreeSpace)
 		{
 			/* use this page as future insert target, too */
@@ -303,16 +303,16 @@ RelationGetBufferForTuple(Relation relation, Size len,
 	 * is empty (this should never happen, but if it does we don't want to
 	 * risk wiping out valid data).
 	 */
-	pageHeader = (Page) BufferGetPage(buffer);
+	page = BufferGetPage(buffer);
 
-	if (!PageIsNew((PageHeader) pageHeader))
+	if (!PageIsNew(page))
 		elog(ERROR, "page %u of relation \"%s\" should be empty but is not",
 			 BufferGetBlockNumber(buffer),
 			 RelationGetRelationName(relation));
 
-	PageInit(pageHeader, BufferGetPageSize(buffer), 0);
+	PageInit(page, BufferGetPageSize(buffer), 0);
 
-	if (len > PageGetHeapFreeSpace(pageHeader))
+	if (len > PageGetHeapFreeSpace(page))
 	{
 		/* We should not get here given the test at the top */
 		elog(PANIC, "tuple is too big: size %lu", (unsigned long) len);

src/backend/access/heap/pruneheap.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/heap/pruneheap.c,v 1.15 2008/06/19 00:46:03 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/heap/pruneheap.c,v 1.16 2008/07/13 20:45:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -72,7 +72,7 @@ static void heap_prune_record_unused(PruneState *prstate, OffsetNumber offnum);
 void
 heap_page_prune_opt(Relation relation, Buffer buffer, TransactionId OldestXmin)
 {
-	PageHeader	dp = (PageHeader) BufferGetPage(buffer);
+	Page		page = BufferGetPage(buffer);
 	Size		minfree;
 
 	/*
@@ -81,7 +81,7 @@ heap_page_prune_opt(Relation relation, Buffer buffer, TransactionId OldestXmin)
 	 * Forget it if page is not hinted to contain something prunable that's
 	 * older than OldestXmin.
 	 */
-	if (!PageIsPrunable(dp, OldestXmin))
+	if (!PageIsPrunable(page, OldestXmin))
 		return;
 
 	/*
@@ -100,7 +100,7 @@ heap_page_prune_opt(Relation relation, Buffer buffer, TransactionId OldestXmin)
 											 HEAP_DEFAULT_FILLFACTOR);
 	minfree = Max(minfree, BLCKSZ / 10);
 
-	if (PageIsFull(dp) || PageGetHeapFreeSpace((Page) dp) < minfree)
+	if (PageIsFull(page) || PageGetHeapFreeSpace(page) < minfree)
 	{
 		/* OK, try to get exclusive buffer lock */
 		if (!ConditionalLockBufferForCleanup(buffer))
@@ -112,7 +112,7 @@ heap_page_prune_opt(Relation relation, Buffer buffer, TransactionId OldestXmin)
 		 * prune. (We needn't recheck PageIsPrunable, since no one else could
 		 * have pruned while we hold pin.)
 		 */
-		if (PageIsFull(dp) || PageGetHeapFreeSpace((Page) dp) < minfree)
+		if (PageIsFull(page) || PageGetHeapFreeSpace(page) < minfree)
 		{
 			/* OK to prune (though not to remove redirects) */
 			(void) heap_page_prune(relation, buffer, OldestXmin, false, true);

src/backend/access/nbtree/nbtpage.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.109 2008/05/12 00:00:45 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.110 2008/07/13 20:45:47 tgl Exp $
  *
  *	NOTES
  *	   Postgres btree pages look like ordinary relation pages.	The opaque
@@ -436,8 +436,7 @@ _bt_checkpage(Relation rel, Buffer buf)
 	/*
 	 * Additionally check that the special area looks sane.
 	 */
-	if (((PageHeader) (page))->pd_special !=
-		(BLCKSZ - MAXALIGN(sizeof(BTPageOpaqueData))))
+	if (PageGetSpecialSize(page) != MAXALIGN(sizeof(BTPageOpaqueData)))
 		ereport(ERROR,
 				(errcode(ERRCODE_INDEX_CORRUPTED),
 				 errmsg("index \"%s\" contains corrupted page at block %u",
@@ -555,7 +554,7 @@ _bt_getbuf(Relation rel, BlockNumber blkno, int access)
 
 		/* Initialize the new page before returning it */
 		page = BufferGetPage(buf);
-		Assert(PageIsNew((PageHeader) page));
+		Assert(PageIsNew(page));
 		_bt_pageinit(page, BufferGetPageSize(buf));
 	}