postgresql/src/include/access/htup.h

/*-------------------------------------------------------------------------
 *
 * htup.h--
 *    POSTGRES heap tuple definitions.
 *
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 * $Id: htup.h,v 1.2 1996/10/19 04:02:39 scrappy Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef	HTUP_H
#define HTUP_H

#include "storage/itemptr.h"
#include "utils/nabstime.h"

#define MinHeapTupleBitmapSize	32		/* 8 * 4 */

/* check these, they are likely to be more severely limited by t_hoff */

#define MaxHeapAttributeNumber	1600		/* 8 * 200 */

/*
 * to avoid wasting space, the attributes should be layed out in such a
 * way to reduce structure padding.
 */
typedef struct HeapTupleData {

    unsigned int	t_len;		/* length of entire tuple */

    ItemPointerData	t_ctid;		/* current TID of this tuple */

    ItemPointerData	t_chain;	/* replaced tuple TID */

    Oid			t_oid;		/* OID of this tuple -- 4 bytes */

    CommandId		t_cmin;		/* insert CID stamp -- 2 bytes each */
    CommandId		t_cmax;		/* delete CommandId stamp */

    TransactionId	t_xmin;		/* insert XID stamp -- 4 bytes each */
    TransactionId	t_xmax;		/* delete XID stamp */

    AbsoluteTime	t_tmin;		/* time stamps -- 4 bytes each */
    AbsoluteTime	t_tmax;	

    int16		t_natts;	/* number of attributes */
    char		t_vtype;	/* not used - padding */

    char		t_infomask;	/* whether tuple as null or variable
					 * length attributes
					 */

    uint8		t_hoff;		/* sizeof tuple header */

    bits8		t_bits[MinHeapTupleBitmapSize / 8];
					/* bit map of domains */

    /* MORE DATA FOLLOWS AT END OF STRUCT */
} HeapTupleData;	

typedef HeapTupleData	*HeapTuple;


#define SelfItemPointerAttributeNumber		(-1)
#define ObjectIdAttributeNumber			(-2)
#define MinTransactionIdAttributeNumber		(-3)
#define MinCommandIdAttributeNumber		(-4)
#define MaxTransactionIdAttributeNumber		(-5)
#define MaxCommandIdAttributeNumber		(-6)
#define ChainItemPointerAttributeNumber		(-7)
#define AnchorItemPointerAttributeNumber	(-8)
#define MinAbsoluteTimeAttributeNumber		(-9)
#define MaxAbsoluteTimeAttributeNumber		(-10)
#define VersionTypeAttributeNumber		(-11)
#define FirstLowInvalidHeapAttributeNumber	(-12)


/* ----------------
 *	support macros
 * ----------------
 */
#define GETSTRUCT(TUP) (((char *)(TUP)) + ((HeapTuple)(TUP))->t_hoff)


/*
 * BITMAPLEN(NATTS) - 
 *	Computes minimum size of bitmap given number of domains.
 */
#define BITMAPLEN(NATTS) \
	((((((int)(NATTS) - 1) >> 3) + 4 - (MinHeapTupleBitmapSize >> 3)) \
	  & ~03) + (MinHeapTupleBitmapSize >> 3))

/*
 * HeapTupleIsValid
 *	True iff the heap tuple is valid.
 */
#define	HeapTupleIsValid(tuple)	PointerIsValid(tuple)

/*
 * information stored in t_infomask:
 */
#define HEAP_HASNULL		0x01	/* has null attribute(s) */
#define	HEAP_HASVARLENA		0x02	/* has variable length attribute(s) */

#define HeapTupleNoNulls(tuple) \
	(!(((HeapTuple) (tuple))->t_infomask & HEAP_HASNULL))

#define HeapTupleAllFixed(tuple) \
	(!(((HeapTuple) (tuple))->t_infomask & HEAP_HASVARLENA))

#endif	/* HTUP_H */