Re: Reduce heap tuple header size II

On Fri, 21 Jun 2002 12:45:48 -0400 (EDT), Bruce Momjian  wrote:
>> > Yes, there are some good ones there, but the idea that somehow they are
>> > all going to hit in the same release seems unlikely.  I say let's do
>> > some now, some later, and move ahead.

I (strongly :-)) agree.

>Well, that is a different argument than initially.  So, it is a valid
>patch, but we have to decide when to apply it.
>
>We can easily hold it until we near release of 7.3.  If pg_upgrade is in
>good shape _and_ no other format changes are required, we can  hold it
>for 7.4.  What happens if 7.4 doesn't have any format changes?
>
>However, if we have other changes or pg_upgrade isn't going to work, we
>can apply it in August.

But what, if the patch causes or reveals a well hidden bug, possibly
somewhere else in the code?  I'd vote for applying it now, so that in
August it already has undergone some testing.  You can always patch -R
before going beta...

>(Manfred, you can be sure I will not lose this patch.)

Thanks.  Anyway, lose it!  Here is a new version.

>So, we have to decide if we apply it now or delay it for later in 7.3,
>or for >=7.4.

Why not let the users decide?  With this new version of the patch they
can
	configure --enable-pg72format
if this patch is the only thing that stops pg_upgrade from working and
if they want to use pg_upgrade.

>My personal vote is that we apply it now, and perhaps try some of the
>other format changes we were going to make.

And with #ifdef PG72FORMAT we can introduce them without very much
risk.  One thing that's still missing is we'd need two entries in
catversion.h.

Servus
 Manfred

diff -u ../base/INSTALL ./INSTALL
--- ../base/INSTALL	2002-01-31 01:46:26.000000000 +0100
+++ ./INSTALL	2002-06-25 15:59:03.000000000 +0200
@@ -283,6 +283,13 @@
           Enables single-byte character set recode support. See the
           Administrator's Guide about this feature.
 
+     --enable-pg72format
+
+          Enables version 7.2 page format, giving you a better chance of
+          converting existing databases by pg_upgrade. Do not use this
+          feature, if you are just starting to use PostgreSQL or if you
+          plan to upgrade via pg_dump/restore.
+
      --enable-multibyte
 
           Allows the use of multibyte character encodings (including
Common subdirectories: ../base/config and ./config
diff -u ../base/configure ./configure
--- ../base/configure	2002-05-29 14:42:20.000000000 +0200
+++ ./configure	2002-06-25 15:51:18.000000000 +0200
@@ -1652,6 +1652,44 @@
 
 
 #
+# Version 7.2 page format (--enable-pg72format)
+#
+echo "$as_me:$LINENO: checking whether to build with version 7.2 page format" >&5
+echo $ECHO_N "checking whether to build with version 7.2 page format... $ECHO_C" >&6
+
+
+# Check whether --enable-pg72format or --disable-pg72format was given.
+if test "${enable_pg72format+set}" = set; then
+  enableval="$enable_pg72format"
+
+  case $enableval in
+    yes)
+
+cat >>confdefs.h <<\_ACEOF
+#define PG72FORMAT 1
+_ACEOF
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      { { echo "$as_me:$LINENO: error: no argument expected for --enable-pg72format option" >&5
+echo "$as_me: error: no argument expected for --enable-pg72format option" >&2;}
+   { (exit 1); exit 1; }; }
+      ;;
+  esac
+
+else
+  enable_pg72format=no
+
+fi;
+
+echo "$as_me:$LINENO: result: $enable_pg72format" >&5
+echo "${ECHO_T}$enable_pg72format" >&6
+
+
+#
 # Multibyte support
 #
 MULTIBYTE=SQL_ASCII
diff -u ../base/configure.in ./configure.in
--- ../base/configure.in	2002-05-29 14:42:20.000000000 +0200
+++ ./configure.in	2002-06-25 15:51:15.000000000 +0200
@@ -162,6 +162,16 @@
 
 
 #
+# Version 7.2 page format (--enable-pg72format)
+#
+AC_MSG_CHECKING([whether to build with version 7.2 page format])
+PGAC_ARG_BOOL(enable, pg72format, no, [  --enable-pg72format     enable version 7.2 page format],
+              [AC_DEFINE([PG72FORMAT], 1,
+                         [Set to 1 if you want version 7.2 page format (--enable-pg72format)])])
+AC_MSG_RESULT([$enable_pg72format])
+
+
+#
 # Multibyte support
 #
 MULTIBYTE=SQL_ASCII
diff -ru ../base/src/backend/access/heap/heapam.c src/backend/access/heap/heapam.c
--- ../base/src/backend/access/heap/heapam.c	2002-06-17 10:11:31.000000000 +0200
+++ src/backend/access/heap/heapam.c	2002-06-17 22:35:32.000000000 +0200
@@ -2204,7 +2204,7 @@
 		htup->t_infomask = HEAP_XMAX_INVALID | xlhdr.mask;
 		HeapTupleHeaderSetXmin(htup, record->xl_xid);
 		HeapTupleHeaderSetCmin(htup, FirstCommandId);
-		HeapTupleHeaderSetXmax(htup, InvalidTransactionId);
+		HeapTupleHeaderSetXmaxInvalid(htup);
 		HeapTupleHeaderSetCmax(htup, FirstCommandId);
 
 		offnum = PageAddItem(page, (Item) htup, newlen, offnum,
diff -ru ../base/src/include/access/htup.h src/include/access/htup.h
--- ../base/src/include/access/htup.h	2002-06-17 10:11:32.000000000 +0200
+++ src/include/access/htup.h	2002-06-25 16:14:37.000000000 +0200
@@ -57,15 +57,33 @@
  * Also note that we omit the nulls bitmap if t_infomask shows that there
  * are no nulls in the tuple.
  */
+/*
+** We store five "virtual" fields Xmin, Cmin, Xmax, Cmax, and Xvac
+** in three physical fields t_xmin, t_cid, t_xmax:
+** CommandId     Cmin;		insert CID stamp
+** CommandId     Cmax;		delete CommandId stamp
+** TransactionId Xmin;		insert XID stamp
+** TransactionId Xmax;		delete XID stamp
+** TransactionId Xvac;		used by VACCUUM
+**
+** This assumes, that a CommandId can be stored in a TransactionId.
+*/
 typedef struct HeapTupleHeaderData
 {
 	Oid			t_oid;			/* OID of this tuple -- 4 bytes */
 
+#ifdef PG72FORMAT
+	/* v7.2: Xvac is stored in t_cmin */
 	CommandId	t_cmin;			/* insert CID stamp -- 4 bytes each */
 	CommandId	t_cmax;			/* delete CommandId stamp */
 
 	TransactionId t_xmin;		/* insert XID stamp -- 4 bytes each */
 	TransactionId t_xmax;		/* delete XID stamp */
+#else
+	TransactionId t_xmin;		/* Xmin -- 4 bytes each */
+	TransactionId t_cid;		/* Cmin, Cmax, Xvac */
+	TransactionId t_xmax;		/* Xmax, Cmax */
+#endif
 
 	ItemPointerData t_ctid;		/* current TID of this or newer tuple */
 
@@ -75,7 +93,7 @@
 
 	uint8		t_hoff;			/* sizeof header incl. bitmap, padding */
 
-	/* ^ - 31 bytes - ^ */
+	/* ^ - 27 (v7.3) or 31 (v7.2) bytes - ^ */
 
 	bits8		t_bits[1];		/* bitmap of NULLs -- VARIABLE LENGTH */
 
@@ -96,6 +114,8 @@
 										 * attribute(s) */
 #define HEAP_HASEXTENDED		0x000C	/* the two above combined */
 
+#define HEAP_XMIN_IS_XMAX		0x0040	/* created and deleted in the */
+										/* same transaction */
 #define HEAP_XMAX_UNLOGGED		0x0080	/* to lock tuple for update */
 										/* without logging */
 #define HEAP_XMIN_COMMITTED		0x0100	/* t_xmin committed */
@@ -108,6 +128,7 @@
 										 * vacuum */
 #define HEAP_MOVED_IN			0x8000	/* moved from another place by
 										 * vacuum */
+#define HEAP_MOVED (HEAP_MOVED_OFF | HEAP_MOVED_IN)
 
 #define HEAP_XACT_MASK			0xFFF0	/* visibility-related bits */
 
@@ -116,8 +137,11 @@
 /* HeapTupleHeader accessor macros */
 
 #define HeapTupleHeaderGetXmin(tup) \
-	((tup)->t_xmin)
+( \
+	(tup)->t_xmin \
+)
 
+#ifdef PG72FORMAT
 #define HeapTupleHeaderGetXmax(tup) \
 	((tup)->t_xmax)
 
@@ -163,6 +187,98 @@
 	AssertMacro((tup)->t_infomask & (HEAP_MOVED_IN | HEAP_MOVED_OFF)), \
 	TransactionIdStore((xid), (TransactionId *) &((tup)->t_cmin)) \
 )
+#else
+#define HeapTupleHeaderGetXmax(tup) \
+( \
+	((tup)->t_infomask & HEAP_XMIN_IS_XMAX) ? \
+		(tup)->t_xmin \
+	: \
+		(tup)->t_xmax \
+)
+
+/* no AssertMacro, because this is read as a system-defined attribute */
+#define HeapTupleHeaderGetCmin(tup) \
+( \
+	((tup)->t_infomask & HEAP_MOVED) ? \
+		FirstCommandId \
+	: \
+	( \
+		((tup)->t_infomask & (HEAP_XMIN_IS_XMAX | HEAP_XMAX_INVALID)) ? \
+			(CommandId) (tup)->t_cid \
+		: \
+			FirstCommandId \
+	) \
+)
+
+#define HeapTupleHeaderGetCmax(tup) \
+( \
+	((tup)->t_infomask & HEAP_MOVED) ? \
+		FirstCommandId \
+	: \
+	( \
+		((tup)->t_infomask & (HEAP_XMIN_IS_XMAX | HEAP_XMAX_INVALID)) ? \
+			(CommandId) (tup)->t_xmax \
+		: \
+			(CommandId) (tup)->t_cid \
+	) \
+)
+
+#define HeapTupleHeaderGetXvac(tup) \
+( \
+	AssertMacro((tup)->t_infomask & HEAP_MOVED), \
+	(tup)->t_cid \
+)
+
+
+#define HeapTupleHeaderSetXmin(tup, xid) \
+( \
+	TransactionIdStore((xid), &(tup)->t_xmin) \
+)
+
+#define HeapTupleHeaderSetXminInvalid(tup) \
+do { \
+	(tup)->t_infomask &= ~HEAP_XMIN_IS_XMAX; \
+	StoreInvalidTransactionId(&(tup)->t_xmin); \
+} while (0)
+
+#define HeapTupleHeaderSetXmax(tup, xid) \
+do { \
+	if (TransactionIdEquals((tup)->t_xmin, (xid))) \
+		(tup)->t_infomask |= HEAP_XMIN_IS_XMAX; \
+	else \
+	{ \
+		(tup)->t_infomask &= ~HEAP_XMIN_IS_XMAX; \
+		TransactionIdStore((xid), &(tup)->t_xmax); \
+	} \
+} while (0)
+
+#define HeapTupleHeaderSetXmaxInvalid(tup) \
+do { \
+	(tup)->t_infomask &= ~HEAP_XMIN_IS_XMAX; \
+	StoreInvalidTransactionId(&(tup)->t_xmax); \
+} while (0)
+
+#define HeapTupleHeaderSetCmin(tup, cid) \
+do { \
+	Assert(!((tup)->t_infomask & HEAP_MOVED)); \
+	TransactionIdStore((TransactionId) (cid), &(tup)->t_cid); \
+} while (0)
+
+#define HeapTupleHeaderSetCmax(tup, cid) \
+do { \
+	Assert(!((tup)->t_infomask & HEAP_MOVED)); \
+	if ((tup)->t_infomask & HEAP_XMIN_IS_XMAX) \
+		TransactionIdStore((TransactionId) (cid), &(tup)->t_xmax); \
+	else \
+		TransactionIdStore((TransactionId) (cid), &(tup)->t_cid); \
+} while (0)
+
+#define HeapTupleHeaderSetXvac(tup, xid) \
+do { \
+	Assert((tup)->t_infomask & HEAP_MOVED); \
+	TransactionIdStore((xid), &(tup)->t_cid); \
+} while (0)
+#endif
 
 
 /*
diff -ru ../base/src/include/pg_config.h.in src/include/pg_config.h.in
--- ../base/src/include/pg_config.h.in	2002-06-17 21:04:03.000000000 +0200
+++ src/include/pg_config.h.in	2002-06-25 16:02:40.000000000 +0200
@@ -39,6 +39,9 @@
 /* Set to 1 if you want cyrillic recode (--enable-recode) */
 #undef CYR_RECODE
 
+/* Set to 1 if you want version 7.2 page format (--enable-pg72format) */
+#undef PG72FORMAT
+
 /* Set to 1 if you want to use multibyte characters (--enable-multibyte) */
 #undef MULTIBYTE