heaptuple.c

关系型数据库 Postgresql 6.5.2

/*-------------------------------------------------------------------------
 *
 * heaptuple.c
 *	  This file contains heap tuple accessor and mutator routines, as well
 *	  as a few various tuple utilities.
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /usr/local/cvsroot/pgsql/src/backend/access/common/heaptuple.c,v 1.53.2.1 1999/08/02 05:24:25 scrappy Exp $
 *
 * NOTES
 *	  The old interface functions have been converted to macros
 *	  and moved to heapam.h
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/heapam.h"
#include "catalog/pg_type.h"

/* Used by heap_getattr() macro, for speed */
long		heap_sysoffset[] = {
/* Only the first one is pass-by-ref, and is handled specially in the macro */
	offsetof(HeapTupleHeaderData, t_ctid),
	offsetof(HeapTupleHeaderData, t_oid),
	offsetof(HeapTupleHeaderData, t_xmin),
	offsetof(HeapTupleHeaderData, t_cmin),
	offsetof(HeapTupleHeaderData, t_xmax),
	offsetof(HeapTupleHeaderData, t_cmax)
};

/* ----------------------------------------------------------------
 *						misc support routines
 * ----------------------------------------------------------------
 */

/* ----------------
 *		ComputeDataSize
 * ----------------
 */
Size
ComputeDataSize(TupleDesc tupleDesc,
				Datum *value,
				char *nulls)
{
	uint32		data_length;
	int			i;
	int			numberOfAttributes = tupleDesc->natts;
	Form_pg_attribute *att = tupleDesc->attrs;

	for (data_length = 0, i = 0; i < numberOfAttributes; i++)
	{
		if (nulls[i] != ' ')
			continue;

		data_length = att_align(data_length, att[i]->attlen, att[i]->attalign);
		data_length = att_addlength(data_length, att[i]->attlen, value[i]);
	}

	return data_length;
}

/* ----------------
 *		DataFill
 * ----------------
 */
void
DataFill(char *data,
		 TupleDesc tupleDesc,
		 Datum *value,
		 char *nulls,
		 uint16 *infomask,
		 bits8 *bit)
{
	bits8	   *bitP = 0;
	int			bitmask = 0;
	uint32		data_length;
	int			i;
	int			numberOfAttributes = tupleDesc->natts;
	Form_pg_attribute *att = tupleDesc->attrs;

	if (bit != NULL)
	{
		bitP = &bit[-1];
		bitmask = CSIGNBIT;
	}

	*infomask = 0;

	for (i = 0; i < numberOfAttributes; i++)
	{
		if (bit != NULL)
		{
			if (bitmask != CSIGNBIT)
				bitmask <<= 1;
			else
			{
				bitP += 1;
				*bitP = 0x0;
				bitmask = 1;
			}

			if (nulls[i] == 'n')
			{
				*infomask |= HEAP_HASNULL;
				continue;
			}

			*bitP |= bitmask;
		}

		data = (char *) att_align((long) data, att[i]->attlen, att[i]->attalign);
		switch (att[i]->attlen)
		{
			case -1:
				*infomask |= HEAP_HASVARLENA;
				data_length = VARSIZE(DatumGetPointer(value[i]));
				memmove(data, DatumGetPointer(value[i]), data_length);
				break;
			case sizeof(char):
				*data = att[i]->attbyval ?
					DatumGetChar(value[i]) : *((char *) value[i]);
				break;
			case sizeof(int16):
				*(short *) data = (att[i]->attbyval ?
								   DatumGetInt16(value[i]) :
								   *((short *) value[i]));
				break;
			case sizeof(int32):
				*(int32 *) data = (att[i]->attbyval ?
								   DatumGetInt32(value[i]) :
								   *((int32 *) value[i]));
				break;
			default:
				memmove(data, DatumGetPointer(value[i]),
						att[i]->attlen);
				break;
		}
		data = (char *) att_addlength((long) data, att[i]->attlen, value[i]);
	}
}

/* ----------------------------------------------------------------
 *						heap tuple interface
 * ----------------------------------------------------------------
 */

/* ----------------
 *		heap_attisnull	- returns 1 iff tuple attribute is not present
 * ----------------
 */
int
heap_attisnull(HeapTuple tup, int attnum)
{
	if (attnum > (int) tup->t_data->t_natts)
		return 1;

	if (HeapTupleNoNulls(tup))
		return 0;

	if (attnum > 0)
		return att_isnull(attnum - 1, tup->t_data->t_bits);
	else
		switch (attnum)
		{
			case SelfItemPointerAttributeNumber:
			case ObjectIdAttributeNumber:
			case MinTransactionIdAttributeNumber:
			case MinCommandIdAttributeNumber:
			case MaxTransactionIdAttributeNumber:
			case MaxCommandIdAttributeNumber:
				break;

			case 0:
				elog(ERROR, "heap_attisnull: zero attnum disallowed");

			default:
				elog(ERROR, "heap_attisnull: undefined negative attnum");
		}

	return 0;
}

/* ----------------------------------------------------------------
 *				 system attribute heap tuple support
 * ----------------------------------------------------------------
 */

/* ----------------
 *		heap_sysattrlen
 *
 *		This routine returns the length of a system attribute.
 * ----------------
 */
int
heap_sysattrlen(AttrNumber attno)
{
	HeapTupleHeader f = NULL;

	switch (attno)
	{
		case SelfItemPointerAttributeNumber:
			return sizeof f->t_ctid;
		case ObjectIdAttributeNumber:
			return sizeof f->t_oid;
		case MinTransactionIdAttributeNumber:
			return sizeof f->t_xmin;
		case MinCommandIdAttributeNumber:
			return sizeof f->t_cmin;
		case MaxTransactionIdAttributeNumber:
			return sizeof f->t_xmax;
		case MaxCommandIdAttributeNumber:
			return sizeof f->t_cmax;

		default:
			elog(ERROR, "sysattrlen: System attribute number %d unknown.", attno);
			return 0;
	}
}

/* ----------------
 *		heap_sysattrbyval
 *
 *		This routine returns the "by-value" property of a system attribute.
 * ----------------
 */
bool
heap_sysattrbyval(AttrNumber attno)
{
	bool		byval;

	switch (attno)
	{
		case SelfItemPointerAttributeNumber:
			byval = false;
			break;
		case ObjectIdAttributeNumber:
			byval = true;
			break;
		case MinTransactionIdAttributeNumber:
			byval = true;
			break;
		case MinCommandIdAttributeNumber:
			byval = true;
			break;
		case MaxTransactionIdAttributeNumber:
			byval = true;
			break;
		case MaxCommandIdAttributeNumber:
			byval = true;
			break;
		default:
			byval = true;
			elog(ERROR, "sysattrbyval: System attribute number %d unknown.",
				 attno);
			break;
	}

	return byval;
}

#ifdef NOT_USED
/* ----------------
 *		heap_getsysattr
 * ----------------
 */
Datum
heap_getsysattr(HeapTuple tup, Buffer b, int attnum)
{
	switch (attnum)
	{
			case SelfItemPointerAttributeNumber:
			return (Datum) &tup->t_ctid;
		case ObjectIdAttributeNumber:
			return (Datum) (long) tup->t_oid;
		case MinTransactionIdAttributeNumber:
			return (Datum) (long) tup->t_xmin;
		case MinCommandIdAttributeNumber:
			return (Datum) (long) tup->t_cmin;
		case MaxTransactionIdAttributeNumber:
			return (Datum) (long) tup->t_xmax;
		case MaxCommandIdAttributeNumber:
			return (Datum) (long) tup->t_cmax;
		default:
			elog(ERROR, "heap_getsysattr: undefined attnum %d", attnum);
	}
	return (Datum) NULL;
}

#endif

/* ----------------
 *		nocachegetattr
 *
 *		This only gets called from fastgetattr() macro, in cases where
 *		we can't use a cacheoffset and the value is not null.
 *
 *		This caches attribute offsets in the attribute descriptor.
 *
 *		An alternate way to speed things up would be to cache offsets
 *		with the tuple, but that seems more difficult unless you take
 *		the storage hit of actually putting those offsets into the
 *		tuple you send to disk.  Yuck.
 *
 *		This scheme will be slightly slower than that, but should
 *		perform well for queries which hit large #'s of tuples.  After
 *		you cache the offsets once, examining all the other tuples using
 *		the same attribute descriptor will go much quicker. -cim 5/4/91
 * ----------------
 */
Datum
nocachegetattr(HeapTuple tuple,
			   int attnum,
			   TupleDesc tupleDesc,
			   bool *isnull)
{
	char	   *tp;				/* ptr to att in tuple */
	HeapTupleHeader tup = tuple->t_data;
	bits8	   *bp = tup->t_bits;		/* ptr to att in tuple */
	Form_pg_attribute *att = tupleDesc->attrs;
	int			slow = 0;		/* do we have to walk nulls? */


#if IN_MACRO
/* This is handled in the macro */
	Assert(attnum > 0);

	if (isnull)
		*isnull = false;
#endif

	attnum--;

	/* ----------------
	 *	 Three cases:
	 *
	 *	 1: No nulls and no variable length attributes.
	 *	 2: Has a null or a varlena AFTER att.
	 *	 3: Has nulls or varlenas BEFORE att.
	 * ----------------
	 */

	if (HeapTupleNoNulls(tuple))
	{
#if IN_MACRO
/* This is handled in the macro */
		if (att[attnum]->attcacheoff != -1)
		{
			return (Datum)
				fetchatt(&(att[attnum]),
				  (char *) tup + tup->t_hoff + att[attnum]->attcacheoff);
		}
		else if (attnum == 0)
		{

			/*
			 * first attribute is always at position zero
			 */
			return (Datum) fetchatt(&(att[0]), (char *) tup + tup->t_hoff);
		}
#endif
	}
	else
	{

		/*
		 * there's a null somewhere in the tuple
		 */

		/* ----------------
		 *		check to see if desired att is null
		 * ----------------
		 */

#if IN_MACRO
/* This is handled in the macro */
		if (att_isnull(attnum, bp))
		{
			if (isnull)
				*isnull = true;
			return (Datum) NULL;
		}
#endif

		/* ----------------
		 *		Now check to see if any preceding bits are null...
		 * ----------------
		 */
		{
			int			byte = attnum >> 3;
			int			finalbit = attnum & 0x07;

			/* check for nulls "before" final bit of last byte */
			if ((~bp[byte]) & ((1 << finalbit) - 1))
				slow = 1;
			else
			{
				/* check for nulls in any "earlier" bytes */
				int			i;

				for (i = 0; i < byte; i++)
				{
					if (bp[i] != 0xFF)
					{
						slow = 1;
						break;
					}
				}
			}
		}
	}