heaptuple.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * heaptuple.c
 *	  This file contains heap tuple accessor and mutator routines, as well
 *	  as various tuple utilities.
 *
 * NOTE: there is massive duplication of code in this module to
 * support both the convention that a null is marked by a bool TRUE,
 * and the convention that a null is marked by a char 'n'.	The latter
 * convention is deprecated but it'll probably be a long time before
 * we can get rid of it entirely.
 *
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/access/common/heaptuple.c,v 1.102.2.1 2005/11/22 18:23:03 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/heapam.h"
#include "access/tuptoaster.h"
#include "catalog/pg_type.h"
#include "executor/tuptable.h"


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

/*
 * heap_compute_data_size
 *		Determine size of the data area of a tuple to be constructed
 */
Size
heap_compute_data_size(TupleDesc tupleDesc,
					   Datum *values,
					   bool *isnull)
{
	Size		data_length = 0;
	int			i;
	int			numberOfAttributes = tupleDesc->natts;
	Form_pg_attribute *att = tupleDesc->attrs;

	for (i = 0; i < numberOfAttributes; i++)
	{
		if (isnull[i])
			continue;

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

	return data_length;
}

/* ----------------
 *		ComputeDataSize
 *
 * Determine size of the data area of a tuple to be constructed
 *
 * OLD API with char 'n'/' ' convention for indicating nulls
 * ----------------
 */
static Size
ComputeDataSize(TupleDesc tupleDesc,
				Datum *values,
				char *nulls)
{
	Size		data_length = 0;
	int			i;
	int			numberOfAttributes = tupleDesc->natts;
	Form_pg_attribute *att = tupleDesc->attrs;

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

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

	return data_length;
}

/*
 * heap_fill_tuple
 *		Load data portion of a tuple from values/isnull arrays
 *
 * We also fill the null bitmap (if any) and set the infomask bits
 * that reflect the tuple's data contents.
 */
void
heap_fill_tuple(TupleDesc tupleDesc,
				Datum *values, bool *isnull,
				char *data, uint16 *infomask, bits8 *bit)
{
	bits8	   *bitP;
	int			bitmask;
	int			i;
	int			numberOfAttributes = tupleDesc->natts;
	Form_pg_attribute *att = tupleDesc->attrs;

	if (bit != NULL)
	{
		bitP = &bit[-1];
		bitmask = CSIGNBIT;
	}
	else
	{
		/* just to keep compiler quiet */
		bitP = NULL;
		bitmask = 0;
	}

	*infomask &= ~(HEAP_HASNULL | HEAP_HASVARWIDTH | HEAP_HASEXTENDED);

	for (i = 0; i < numberOfAttributes; i++)
	{
		Size		data_length;

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

			if (isnull[i])
			{
				*infomask |= HEAP_HASNULL;
				continue;
			}

			*bitP |= bitmask;
		}

		/* XXX we are aligning the pointer itself, not the offset */
		data = (char *) att_align((long) data, att[i]->attalign);

		if (att[i]->attbyval)
		{
			/* pass-by-value */
			store_att_byval(data, values[i], att[i]->attlen);
			data_length = att[i]->attlen;
		}
		else if (att[i]->attlen == -1)
		{
			/* varlena */
			*infomask |= HEAP_HASVARWIDTH;
			if (VARATT_IS_EXTERNAL(values[i]))
				*infomask |= HEAP_HASEXTERNAL;
			if (VARATT_IS_COMPRESSED(values[i]))
				*infomask |= HEAP_HASCOMPRESSED;
			data_length = VARATT_SIZE(DatumGetPointer(values[i]));
			memcpy(data, DatumGetPointer(values[i]), data_length);
		}
		else if (att[i]->attlen == -2)
		{
			/* cstring */
			*infomask |= HEAP_HASVARWIDTH;
			data_length = strlen(DatumGetCString(values[i])) + 1;
			memcpy(data, DatumGetPointer(values[i]), data_length);
		}
		else
		{
			/* fixed-length pass-by-reference */
			Assert(att[i]->attlen > 0);
			data_length = att[i]->attlen;
			memcpy(data, DatumGetPointer(values[i]), data_length);
		}

		data += data_length;
	}
}

/* ----------------
 *		DataFill
 *
 * Load data portion of a tuple from values/nulls arrays
 *
 * OLD API with char 'n'/' ' convention for indicating nulls
 * ----------------
 */
static void
DataFill(char *data,
		 TupleDesc tupleDesc,
		 Datum *values,
		 char *nulls,
		 uint16 *infomask,
		 bits8 *bit)
{
	bits8	   *bitP;
	int			bitmask;
	int			i;
	int			numberOfAttributes = tupleDesc->natts;
	Form_pg_attribute *att = tupleDesc->attrs;

	if (bit != NULL)
	{
		bitP = &bit[-1];
		bitmask = CSIGNBIT;
	}
	else
	{
		/* just to keep compiler quiet */
		bitP = NULL;
		bitmask = 0;
	}

	*infomask &= ~(HEAP_HASNULL | HEAP_HASVARWIDTH | HEAP_HASEXTENDED);

	for (i = 0; i < numberOfAttributes; i++)
	{
		Size		data_length;

		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;
		}

		/* XXX we are aligning the pointer itself, not the offset */
		data = (char *) att_align((long) data, att[i]->attalign);

		if (att[i]->attbyval)
		{
			/* pass-by-value */
			store_att_byval(data, values[i], att[i]->attlen);
			data_length = att[i]->attlen;
		}
		else if (att[i]->attlen == -1)
		{
			/* varlena */
			*infomask |= HEAP_HASVARWIDTH;
			if (VARATT_IS_EXTERNAL(values[i]))
				*infomask |= HEAP_HASEXTERNAL;
			if (VARATT_IS_COMPRESSED(values[i]))
				*infomask |= HEAP_HASCOMPRESSED;
			data_length = VARATT_SIZE(DatumGetPointer(values[i]));
			memcpy(data, DatumGetPointer(values[i]), data_length);
		}
		else if (att[i]->attlen == -2)
		{
			/* cstring */
			*infomask |= HEAP_HASVARWIDTH;
			data_length = strlen(DatumGetCString(values[i])) + 1;
			memcpy(data, DatumGetPointer(values[i]), data_length);
		}
		else
		{
			/* fixed-length pass-by-reference */
			Assert(att[i]->attlen > 0);
			data_length = att[i]->attlen;
			memcpy(data, DatumGetPointer(values[i]), data_length);
		}

		data += data_length;
	}
}

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

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

	if (attnum > 0)
	{
		if (HeapTupleNoNulls(tup))
			return false;
		return att_isnull(attnum - 1, tup->t_data->t_bits);
	}

	switch (attnum)
	{
		case TableOidAttributeNumber:
		case SelfItemPointerAttributeNumber:
		case ObjectIdAttributeNumber:
		case MinTransactionIdAttributeNumber:
		case MinCommandIdAttributeNumber:
		case MaxTransactionIdAttributeNumber:
		case MaxCommandIdAttributeNumber:
			/* these are never null */
			break;

		default:
			elog(ERROR, "invalid attnum: %d", attnum);
	}

	return false;
}

/* ----------------
 *		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
 *
 *		NOTE: if you need to change this code, see also heap_deform_tuple.
 * ----------------
 */
Datum
nocachegetattr(HeapTuple tuple,
			   int attnum,
			   TupleDesc tupleDesc,
			   bool *isnull)
{
	HeapTupleHeader tup = tuple->t_data;
	Form_pg_attribute *att = tupleDesc->attrs;
	char	   *tp;				/* ptr to att in tuple */
	bits8	   *bp = tup->t_bits;		/* ptr to null bitmap in tuple */
	bool		slow = false;	/* do we have to walk nulls? */

	(void) isnull;				/* not used */
#ifdef 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-width attributes.
	 *	 2: Has a null or a var-width AFTER att.
	 *	 3: Has nulls or var-widths BEFORE att.
	 * ----------------
	 */

	if (HeapTupleNoNulls(tuple))
	{
#ifdef IN_MACRO
/* This is handled in the macro */
		if (att[attnum]->attcacheoff != -1)
		{
			return fetchatt(att[attnum],
							(char *) tup + tup->t_hoff +
							att[attnum]->attcacheoff);
		}
#endif
	}
	else
	{
		/*
		 * there's a null somewhere in the tuple
		 *
		 * check to see if desired att is null
		 */

#ifdef 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 = true;
			else
			{
				/* check for nulls in any "earlier" bytes */
				int			i;

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

	tp = (char *) tup + tup->t_hoff;

	/*
	 * now check for any non-fixed length attrs before our attribute
	 */
	if (!slow)
	{
		if (att[attnum]->attcacheoff != -1)
		{
			return fetchatt(att[attnum],
							tp + att[attnum]->attcacheoff);
		}
		else if (HeapTupleHasVarWidth(tuple))
		{
			int			j;

			/*
			 * In for(), we test <= and not < because we want to see if we can
			 * go past it in initializing offsets.
			 */
			for (j = 0; j <= attnum; j++)
			{
				if (att[j]->attlen <= 0)
				{
					slow = true;
					break;
				}
			}
		}
	}

	/*
	 * If slow is false, and we got here, we know that we have a tuple with no
	 * nulls or var-widths before the target attribute. If possible, we also
	 * want to initialize the remainder of the attribute cached offset values.
	 */
	if (!slow)
	{
		int			j = 1;
		long		off;

		/*
		 * need to set cache for some atts
		 */

		att[0]->attcacheoff = 0;

		while (j < attnum && att[j]->attcacheoff > 0)
			j++;

		off = att[j - 1]->attcacheoff + att[j - 1]->attlen;

		for (; j <= attnum ||
		/* Can we compute more?  We will probably need them */
			 (j < tup->t_natts &&
			  att[j]->attcacheoff == -1 &&
			  (HeapTupleNoNulls(tuple) || !att_isnull(j, bp)) &&
			  (HeapTupleAllFixed(tuple) || att[j]->attlen > 0)); j++)
		{
			off = att_align(off, att[j]->attalign);

			att[j]->attcacheoff = off;

			off = att_addlength(off, att[j]->attlen, tp + off);
		}

		return fetchatt(att[attnum], tp + att[attnum]->attcacheoff);
	}
	else
	{
		bool		usecache = true;
		int			off = 0;
		int			i;

		/*
		 * Now we know that we have to walk the tuple CAREFULLY.
		 *
		 * Note - This loop is a little tricky.  For each non-null attribute,
		 * we have to first account for alignment padding before the attr,
		 * then advance over the attr based on its length.	Nulls have no
		 * storage and no alignment padding either.  We can use/set
		 * attcacheoff until we pass either a null or a var-width attribute.
		 */

		for (i = 0; i < attnum; i++)
		{
			if (HeapTupleHasNulls(tuple) && att_isnull(i, bp))
			{
				usecache = false;
				continue;