TOAST mop-up work: update comments for tuple-size-related symbols such

as MaxHeapAttributeNumber.  Increase MaxAttrSize to something more
reasonable (given what it's used for, namely checking char(n) declarations,
I didn't make it the full 1G that it could theoretically be --- 10Mb
seemed a more reasonable number).  Improve calculation of MaxTupleSize.

1 files changed, 23 insertions, 13 deletions

diff --git a/src/include/storage/itemid.h b/src/include/storage/itemid.h
index 51af7f49f3..87aa82ac3c 100644
--- a/src/include/storage/itemid.h
+++ b/src/include/storage/itemid.h
@@ -7,38 +7,48 @@
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: itemid.h,v 1.10 2000/01/26 05:58:33 momjian Exp $
+ * $Id: itemid.h,v 1.11 2000/08/07 20:15:50 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #ifndef ITEMID_H
 #define ITEMID_H
 
-typedef uint16 ItemOffset;
-typedef uint16 ItemLength;
-
-typedef bits16 ItemIdFlags;
-
-
 
+/*
+ * An item pointer (also called line pointer) on a buffer page
+ */
 typedef struct ItemIdData
 {								/* line pointers */
-	unsigned	lp_off:15,		/* offset to find tup */
-	/* can be reduced by 2 if necc. */
-				lp_flags:2,		/* flags on tuple */
+	unsigned	lp_off:15,		/* offset to start of tuple */
+				lp_flags:2,		/* flags for tuple */
 				lp_len:15;		/* length of tuple */
 } ItemIdData;
 
-typedef struct ItemIdData *ItemId;
+typedef ItemIdData *ItemId;
 
-#ifndef LP_USED
+/*
+ * lp_flags contains these flags:
+ */
 #define LP_USED			0x01	/* this line pointer is being used */
-#endif
+/* currently, there is one unused flag bit ... */
+
+
+/*
+ * Item offsets, lengths, and flags are represented by these types when
+ * they're not actually stored in an ItemIdData.
+ */
+typedef uint16 ItemOffset;
+typedef uint16 ItemLength;
+
+typedef bits16 ItemIdFlags;
+
 
 /* ----------------
  *		support macros
  * ----------------
  */
+
 /*
  *		ItemIdGetLength
  */