5 files changed, 19 insertions, 24 deletions
diff --git a/src/include/access/hash.h b/src/include/access/hash.h
index 4d8cd79e9a8..0dab2b6ae91 100644
--- a/src/include/access/hash.h
+++ b/src/include/access/hash.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/hash.h,v 1.88 2008/06/19 00:46:05 alvherre Exp $
+ * $PostgreSQL: pgsql/src/include/access/hash.h,v 1.89 2008/07/13 20:45:47 tgl Exp $
  *
  * NOTES
  *		modeled after Margo Seltzer's hash implementation for unix.
@@ -166,10 +166,10 @@ typedef HashMetaPageData *HashMetaPage;
  * Maximum size of a hash index item (it's okay to have only one per page)
  */
 #define HashMaxItemSize(page) \
-	(PageGetPageSize(page) - \
-	 sizeof(PageHeaderData) - \
-	 MAXALIGN(sizeof(HashPageOpaqueData)) - \
-	 sizeof(ItemIdData))
+	MAXALIGN_DOWN(PageGetPageSize(page) - \
+				  SizeOfPageHeaderData - \
+				  sizeof(ItemIdData) - \
+				  MAXALIGN(sizeof(HashPageOpaqueData)))
 
 #define HASH_MIN_FILLFACTOR			10
 #define HASH_DEFAULT_FILLFACTOR		75
diff --git a/src/include/access/htup.h b/src/include/access/htup.h
index 7a77d438933..8bfdf26697e 100644
--- a/src/include/access/htup.h
+++ b/src/include/access/htup.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/htup.h,v 1.99 2008/05/12 00:00:53 alvherre Exp $
+ * $PostgreSQL: pgsql/src/include/access/htup.h,v 1.100 2008/07/13 20:45:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -362,12 +362,12 @@ do { \
  * other stuff that has to be on a disk page.  Since heap pages use no
  * "special space", there's no deduction for that.
  *
- * NOTE: we do not need to count an ItemId for the tuple because
- * sizeof(PageHeaderData) includes the first ItemId on the page.  But beware
- * of assuming that, say, you can fit 2 tuples of size MaxHeapTupleSize/2
- * on the same page.
+ * NOTE: we allow for the ItemId that must point to the tuple, ensuring that
+ * an otherwise-empty page can indeed hold a tuple of this size.  Because
+ * ItemIds and tuples have different alignment requirements, don't assume that
+ * you can, say, fit 2 tuples of size MaxHeapTupleSize/2 on the same page.
  */
-#define MaxHeapTupleSize  (BLCKSZ - MAXALIGN(sizeof(PageHeaderData)))
+#define MaxHeapTupleSize  (BLCKSZ - MAXALIGN(SizeOfPageHeaderData + sizeof(ItemIdData)))
 
 /*
  * MaxHeapTuplesPerPage is an upper bound on the number of tuples that can
@@ -381,7 +381,7 @@ do { \
  * require increases in the size of work arrays.
  */
 #define MaxHeapTuplesPerPage	\
-	((int) ((BLCKSZ - offsetof(PageHeaderData, pd_linp)) / \
+	((int) ((BLCKSZ - SizeOfPageHeaderData) / \
 			(MAXALIGN(offsetof(HeapTupleHeaderData, t_bits)) + sizeof(ItemIdData))))
 
 /*
diff --git a/src/include/access/itup.h b/src/include/access/itup.h
index eb637b81ea4..ae53accde7c 100644
--- a/src/include/access/itup.h
+++ b/src/include/access/itup.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/itup.h,v 1.49 2008/01/01 19:45:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/access/itup.h,v 1.50 2008/07/13 20:45:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -134,7 +134,7 @@ typedef IndexAttributeBitMapData *IndexAttributeBitMap;
  * must be maxaligned, and it must have an associated item pointer.
  */
 #define MaxIndexTuplesPerPage	\
-	((int) ((BLCKSZ - offsetof(PageHeaderData, pd_linp)) / \
+	((int) ((BLCKSZ - SizeOfPageHeaderData) / \
 			(MAXALIGN(sizeof(IndexTupleData) + 1) + sizeof(ItemIdData))))
 
 
diff --git a/src/include/access/nbtree.h b/src/include/access/nbtree.h
index 9b0e8d0cf77..e0bc10c0642 100644
--- a/src/include/access/nbtree.h
+++ b/src/include/access/nbtree.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/nbtree.h,v 1.120 2008/06/19 00:46:06 alvherre Exp $
+ * $PostgreSQL: pgsql/src/include/access/nbtree.h,v 1.121 2008/07/13 20:45:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -113,13 +113,10 @@ typedef struct BTMetaPageData
  *
  * We actually need to be able to fit three items on every page,
  * so restrict any one item to 1/3 the per-page available space.
- *
- * Note: sizeof(PageHeaderData) includes the first ItemId, but we have
- * to allow for 2 more, as well as the end-of-page special space.
  */
 #define BTMaxItemSize(page) \
 	MAXALIGN_DOWN((PageGetPageSize(page) - \
-				   MAXALIGN(sizeof(PageHeaderData) + 2*sizeof(ItemIdData)) - \
+				   MAXALIGN(SizeOfPageHeaderData + 3*sizeof(ItemIdData)) - \
 				   MAXALIGN(sizeof(BTPageOpaqueData))) / 3)
 
 /*
diff --git a/src/include/access/tuptoaster.h b/src/include/access/tuptoaster.h
index 7d1ba7d2f82..a87aee62dfc 100644
--- a/src/include/access/tuptoaster.h
+++ b/src/include/access/tuptoaster.h
@@ -6,7 +6,7 @@
  *
  * Copyright (c) 2000-2008, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/include/access/tuptoaster.h,v 1.40 2008/06/19 00:46:06 alvherre Exp $
+ * $PostgreSQL: pgsql/src/include/access/tuptoaster.h,v 1.41 2008/07/13 20:45:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -46,10 +46,9 @@
  */
 #define TOAST_TUPLES_PER_PAGE	4
 
-/* Note: sizeof(PageHeaderData) includes the first ItemId on the page */
 #define TOAST_TUPLE_THRESHOLD	\
 	MAXALIGN_DOWN((BLCKSZ - \
-				   MAXALIGN(sizeof(PageHeaderData) + (TOAST_TUPLES_PER_PAGE-1) * sizeof(ItemIdData))) \
+				   MAXALIGN(SizeOfPageHeaderData + TOAST_TUPLES_PER_PAGE * sizeof(ItemIdData))) \
 				  / TOAST_TUPLES_PER_PAGE)
 
 #define TOAST_TUPLE_TARGET		TOAST_TUPLE_THRESHOLD
@@ -73,10 +72,9 @@
  */
 #define EXTERN_TUPLES_PER_PAGE	4		/* tweak only this */
 
-/* Note: sizeof(PageHeaderData) includes the first ItemId on the page */
 #define EXTERN_TUPLE_MAX_SIZE	\
 	MAXALIGN_DOWN((BLCKSZ - \
-				   MAXALIGN(sizeof(PageHeaderData) + (EXTERN_TUPLES_PER_PAGE-1) * sizeof(ItemIdData))) \
+				   MAXALIGN(SizeOfPageHeaderData + EXTERN_TUPLES_PER_PAGE * sizeof(ItemIdData))) \
 				  / EXTERN_TUPLES_PER_PAGE)
 
 #define TOAST_MAX_CHUNK_SIZE	\