Re: Reduce heap tuple header size

Your patch has been added to the PostgreSQL unapplied patches list at:

http://candle.pha.pa.us/cgi-bin/pgpatches

I will try to apply it within the next 48 hours.

---------------------------------------------------------------------------

Manfred Koizar wrote:
> This patch, which is built upon the "HeapTupleHeader accessor macros"
> patch from 2002-06-10, is supposed to reduce the heap tuple header size
> by four bytes on most architectures. Of course it changes the on-disk
> tuple format and therefore requires initdb. As I have (once more)
> opened my mouth too wide, I'll have to provide a heap file conversion
> utility, if this patch gets accepted... More on this later.
>
> ======================
> All 81 tests passed.
> ======================
>
> It's late now, I'll do more tests tomorrow.
>
> Good night
> Manfred
>
> diff -ru ../orig/src/backend/access/heap/heapam.c src/backend/access/heap/heapam.c
> --- ../orig/src/backend/access/heap/heapam.c 2002-06-13 19:34:48.000000000 +0200
> +++ src/backend/access/heap/heapam.c 2002-06-13 22:31:42.000000000 +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 ../orig/src/include/access/htup.h src/include/access/htup.h
> --- ../orig/src/include/access/htup.h 2002-06-13 19:34:49.000000000 +0200
> +++ src/include/access/htup.h 2002-06-14 01:12:47.000000000 +0200
> @@ -57,15 +57,24 @@
> * 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 */
>
> - 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 */
> + TransactionId t_xmin; /* Xmin -- 4 bytes each */
> + TransactionId t_cid; /* Cmin, Cmax, Xvac */
> + TransactionId t_xmax; /* Xmax, Cmax */
>
> ItemPointerData t_ctid; /* current TID of this or newer tuple */
>
> @@ -75,7 +84,7 @@
>
> uint8 t_hoff; /* sizeof header incl. bitmap, padding */
>
> - /* ^ - 31 bytes - ^ */
> + /* ^ - 27 bytes - ^ */
>
> bits8 t_bits[1]; /* bitmap of NULLs -- VARIABLE LENGTH */
>
> @@ -96,6 +105,8 @@
> * 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 +119,7 @@
> * 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 */
>
> @@ -116,53 +128,100 @@
> /* HeapTupleHeader accessor macros */
>
> #define HeapTupleHeaderGetXmin(tup) \
> - ((tup)->t_xmin)
> +( \
> + (tup)->t_xmin \
> +)
>
> #define HeapTupleHeaderGetXmax(tup) \
> - ((tup)->t_xmax)
> +( \
> + ((tup)->t_infomask & HEAP_XMIN_IS_XMAX) ? \
> + (tup)->t_xmin \
> + : \
> + (tup)->t_xmax \
> +)
>
> -/* no AssertMacro, because this is read as a system-defined attribute also */
> +/* no AssertMacro, because this is read as a system-defined attribute */
> #define HeapTupleHeaderGetCmin(tup) \
> ( \
> - (tup)->t_cmin \
> + ((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_cmax)
> +( \
> + ((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_IN | HEAP_MOVED_OFF)), \
> - (TransactionId) (tup)->t_cmin \
> + AssertMacro((tup)->t_infomask & HEAP_MOVED), \
> + (tup)->t_cid \
> )
>
>
> #define HeapTupleHeaderSetXmin(tup, xid) \
> - (TransactionIdStore((xid), &(tup)->t_xmin))
> +( \
> + TransactionIdStore((xid), &(tup)->t_xmin) \
> +)
>
> #define HeapTupleHeaderSetXminInvalid(tup) \
> - (StoreInvalidTransactionId(&(tup)->t_xmin))
> +do { \
> + (tup)->t_infomask &= ~HEAP_XMIN_IS_XMAX; \
> + StoreInvalidTransactionId(&(tup)->t_xmin); \
> +} while (0)
>
> #define HeapTupleHeaderSetXmax(tup, xid) \
> - (TransactionIdStore((xid), &(tup)->t_xmax))
> +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) \
> - (StoreInvalidTransactionId(&(tup)->t_xmax))
> +do { \
> + (tup)->t_infomask &= ~HEAP_XMIN_IS_XMAX; \
> + StoreInvalidTransactionId(&(tup)->t_xmax); \
> +} while (0)
>
> #define HeapTupleHeaderSetCmin(tup, cid) \
> -( \
> - AssertMacro(!((tup)->t_infomask & (HEAP_MOVED_IN | HEAP_MOVED_OFF))), \
> - (tup)->t_cmin = (cid) \
> -)
> +do { \
> + Assert(!((tup)->t_infomask & HEAP_MOVED)); \
> + TransactionIdStore((TransactionId) (cid), &(tup)->t_cid); \
> +} while (0)
>
> #define HeapTupleHeaderSetCmax(tup, cid) \
> - ((tup)->t_cmax = (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) \
> -( \
> - AssertMacro((tup)->t_infomask & (HEAP_MOVED_IN | HEAP_MOVED_OFF)), \
> - TransactionIdStore((xid), (TransactionId *) &((tup)->t_cmin)) \
> -)
> +do { \
> + Assert((tup)->t_infomask & HEAP_MOVED); \
> + TransactionIdStore((xid), &(tup)->t_cid); \
> +} while (0)
>
>
> /*
>
>
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--
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