heaptuple.c

postgresql8.3.4源码,开源数据库

				slow = true;
			}
		}
		else
		{
			/* not varlena, so safe to use att_align_nominal */
			off = att_align_nominal(off, thisatt->attalign);

			if (!slow)
				thisatt->attcacheoff = off;
		}

		values[attnum] = fetchatt(thisatt, tp + off);

		off = att_addlength_pointer(off, thisatt->attlen, tp + off);

		if (thisatt->attlen <= 0)
			slow = true;		/* can't use attcacheoff anymore */
	}

	/*
	 * Save state for next execution
	 */
	slot->tts_nvalid = attnum;
	slot->tts_off = off;
	slot->tts_slow = slow;
}

/*
 * slot_getattr
 *		This function fetches an attribute of the slot's current tuple.
 *		It is functionally equivalent to heap_getattr, but fetches of
 *		multiple attributes of the same tuple will be optimized better,
 *		because we avoid O(N^2) behavior from multiple calls of
 *		nocachegetattr(), even when attcacheoff isn't usable.
 *
 *		A difference from raw heap_getattr is that attnums beyond the
 *		slot's tupdesc's last attribute will be considered NULL even
 *		when the physical tuple is longer than the tupdesc.
 */
Datum
slot_getattr(TupleTableSlot *slot, int attnum, bool *isnull)
{
	HeapTuple	tuple = slot->tts_tuple;
	TupleDesc	tupleDesc = slot->tts_tupleDescriptor;
	HeapTupleHeader tup;

	/*
	 * system attributes are handled by heap_getsysattr
	 */
	if (attnum <= 0)
	{
		if (tuple == NULL)		/* internal error */
			elog(ERROR, "cannot extract system attribute from virtual tuple");
		if (slot->tts_mintuple) /* internal error */
			elog(ERROR, "cannot extract system attribute from minimal tuple");
		return heap_getsysattr(tuple, attnum, tupleDesc, isnull);
	}

	/*
	 * fast path if desired attribute already cached
	 */
	if (attnum <= slot->tts_nvalid)
	{
		*isnull = slot->tts_isnull[attnum - 1];
		return slot->tts_values[attnum - 1];
	}

	/*
	 * return NULL if attnum is out of range according to the tupdesc
	 */
	if (attnum > tupleDesc->natts)
	{
		*isnull = true;
		return (Datum) 0;
	}

	/*
	 * otherwise we had better have a physical tuple (tts_nvalid should equal
	 * natts in all virtual-tuple cases)
	 */
	if (tuple == NULL)			/* internal error */
		elog(ERROR, "cannot extract attribute from empty tuple slot");

	/*
	 * return NULL if attnum is out of range according to the tuple
	 *
	 * (We have to check this separately because of various inheritance and
	 * table-alteration scenarios: the tuple could be either longer or shorter
	 * than the tupdesc.)
	 */
	tup = tuple->t_data;
	if (attnum > HeapTupleHeaderGetNatts(tup))
	{
		*isnull = true;
		return (Datum) 0;
	}

	/*
	 * check if target attribute is null: no point in groveling through tuple
	 */
	if (HeapTupleHasNulls(tuple) && att_isnull(attnum - 1, tup->t_bits))
	{
		*isnull = true;
		return (Datum) 0;
	}

	/*
	 * If the attribute's column has been dropped, we force a NULL result.
	 * This case should not happen in normal use, but it could happen if we
	 * are executing a plan cached before the column was dropped.
	 */
	if (tupleDesc->attrs[attnum - 1]->attisdropped)
	{
		*isnull = true;
		return (Datum) 0;
	}

	/*
	 * Extract the attribute, along with any preceding attributes.
	 */
	slot_deform_tuple(slot, attnum);

	/*
	 * The result is acquired from tts_values array.
	 */
	*isnull = slot->tts_isnull[attnum - 1];
	return slot->tts_values[attnum - 1];
}

/*
 * slot_getallattrs
 *		This function forces all the entries of the slot's Datum/isnull
 *		arrays to be valid.  The caller may then extract data directly
 *		from those arrays instead of using slot_getattr.
 */
void
slot_getallattrs(TupleTableSlot *slot)
{
	int			tdesc_natts = slot->tts_tupleDescriptor->natts;
	int			attnum;
	HeapTuple	tuple;

	/* Quick out if we have 'em all already */
	if (slot->tts_nvalid == tdesc_natts)
		return;

	/*
	 * otherwise we had better have a physical tuple (tts_nvalid should equal
	 * natts in all virtual-tuple cases)
	 */
	tuple = slot->tts_tuple;
	if (tuple == NULL)			/* internal error */
		elog(ERROR, "cannot extract attribute from empty tuple slot");

	/*
	 * load up any slots available from physical tuple
	 */
	attnum = HeapTupleHeaderGetNatts(tuple->t_data);
	attnum = Min(attnum, tdesc_natts);

	slot_deform_tuple(slot, attnum);

	/*
	 * If tuple doesn't have all the atts indicated by tupleDesc, read the
	 * rest as null
	 */
	for (; attnum < tdesc_natts; attnum++)
	{
		slot->tts_values[attnum] = (Datum) 0;
		slot->tts_isnull[attnum] = true;
	}
	slot->tts_nvalid = tdesc_natts;
}

/*
 * slot_getsomeattrs
 *		This function forces the entries of the slot's Datum/isnull
 *		arrays to be valid at least up through the attnum'th entry.
 */
void
slot_getsomeattrs(TupleTableSlot *slot, int attnum)
{
	HeapTuple	tuple;
	int			attno;

	/* Quick out if we have 'em all already */
	if (slot->tts_nvalid >= attnum)
		return;

	/* Check for caller error */
	if (attnum <= 0 || attnum > slot->tts_tupleDescriptor->natts)
		elog(ERROR, "invalid attribute number %d", attnum);

	/*
	 * otherwise we had better have a physical tuple (tts_nvalid should equal
	 * natts in all virtual-tuple cases)
	 */
	tuple = slot->tts_tuple;
	if (tuple == NULL)			/* internal error */
		elog(ERROR, "cannot extract attribute from empty tuple slot");

	/*
	 * load up any slots available from physical tuple
	 */
	attno = HeapTupleHeaderGetNatts(tuple->t_data);
	attno = Min(attno, attnum);

	slot_deform_tuple(slot, attno);

	/*
	 * If tuple doesn't have all the atts indicated by tupleDesc, read the
	 * rest as null
	 */
	for (; attno < attnum; attno++)
	{
		slot->tts_values[attno] = (Datum) 0;
		slot->tts_isnull[attno] = true;
	}
	slot->tts_nvalid = attnum;
}

/*
 * slot_attisnull
 *		Detect whether an attribute of the slot is null, without
 *		actually fetching it.
 */
bool
slot_attisnull(TupleTableSlot *slot, int attnum)
{
	HeapTuple	tuple = slot->tts_tuple;
	TupleDesc	tupleDesc = slot->tts_tupleDescriptor;

	/*
	 * system attributes are handled by heap_attisnull
	 */
	if (attnum <= 0)
	{
		if (tuple == NULL)		/* internal error */
			elog(ERROR, "cannot extract system attribute from virtual tuple");
		if (slot->tts_mintuple) /* internal error */
			elog(ERROR, "cannot extract system attribute from minimal tuple");
		return heap_attisnull(tuple, attnum);
	}

	/*
	 * fast path if desired attribute already cached
	 */
	if (attnum <= slot->tts_nvalid)
		return slot->tts_isnull[attnum - 1];

	/*
	 * return NULL if attnum is out of range according to the tupdesc
	 */
	if (attnum > tupleDesc->natts)
		return true;

	/*
	 * otherwise we had better have a physical tuple (tts_nvalid should equal
	 * natts in all virtual-tuple cases)
	 */
	if (tuple == NULL)			/* internal error */
		elog(ERROR, "cannot extract attribute from empty tuple slot");

	/* and let the tuple tell it */
	return heap_attisnull(tuple, attnum);
}

/*
 * heap_freetuple
 */
void
heap_freetuple(HeapTuple htup)
{
	pfree(htup);
}


/*
 * heap_form_minimal_tuple
 *		construct a MinimalTuple from the given values[] and isnull[] arrays,
 *		which are of the length indicated by tupleDescriptor->natts
 *
 * This is exactly like heap_form_tuple() except that the result is a
 * "minimal" tuple lacking a HeapTupleData header as well as room for system
 * columns.
 *
 * The result is allocated in the current memory context.
 */
MinimalTuple
heap_form_minimal_tuple(TupleDesc tupleDescriptor,
						Datum *values,
						bool *isnull)
{
	MinimalTuple tuple;			/* return tuple */
	Size		len,
				data_len;
	int			hoff;
	bool		hasnull = false;
	Form_pg_attribute *att = tupleDescriptor->attrs;
	int			numberOfAttributes = tupleDescriptor->natts;
	int			i;

	if (numberOfAttributes > MaxTupleAttributeNumber)
		ereport(ERROR,
				(errcode(ERRCODE_TOO_MANY_COLUMNS),
				 errmsg("number of columns (%d) exceeds limit (%d)",
						numberOfAttributes, MaxTupleAttributeNumber)));

	/*
	 * Check for nulls and embedded tuples; expand any toasted attributes in
	 * embedded tuples.  This preserves the invariant that toasting can only
	 * go one level deep.
	 *
	 * We can skip calling toast_flatten_tuple_attribute() if the attribute
	 * couldn't possibly be of composite type.  All composite datums are
	 * varlena and have alignment 'd'; furthermore they aren't arrays. Also,
	 * if an attribute is already toasted, it must have been sent to disk
	 * already and so cannot contain toasted attributes.
	 */
	for (i = 0; i < numberOfAttributes; i++)
	{
		if (isnull[i])
			hasnull = true;
		else if (att[i]->attlen == -1 &&
				 att[i]->attalign == 'd' &&
				 att[i]->attndims == 0 &&
				 !VARATT_IS_EXTENDED(values[i]))
		{
			values[i] = toast_flatten_tuple_attribute(values[i],
													  att[i]->atttypid,
													  att[i]->atttypmod);
		}
	}

	/*
	 * Determine total space needed
	 */
	len = offsetof(MinimalTupleData, t_bits);

	if (hasnull)
		len += BITMAPLEN(numberOfAttributes);

	if (tupleDescriptor->tdhasoid)
		len += sizeof(Oid);

	hoff = len = MAXALIGN(len); /* align user data safely */

	data_len = heap_compute_data_size(tupleDescriptor, values, isnull);

	len += data_len;

	/*
	 * Allocate and zero the space needed.
	 */
	tuple = (MinimalTuple) palloc0(len);

	/*
	 * And fill in the information.
	 */
	tuple->t_len = len;
	HeapTupleHeaderSetNatts(tuple, numberOfAttributes);
	tuple->t_hoff = hoff + MINIMAL_TUPLE_OFFSET;

	if (tupleDescriptor->tdhasoid)		/* else leave infomask = 0 */
		tuple->t_infomask = HEAP_HASOID;

	heap_fill_tuple(tupleDescriptor,
					values,
					isnull,
					(char *) tuple + hoff,
					data_len,
					&tuple->t_infomask,
					(hasnull ? tuple->t_bits : NULL));

	return tuple;
}

/*
 * heap_free_minimal_tuple
 */
void
heap_free_minimal_tuple(MinimalTuple mtup)
{
	pfree(mtup);
}

/*
 * heap_copy_minimal_tuple
 *		copy a MinimalTuple
 *
 * The result is allocated in the current memory context.
 */
MinimalTuple
heap_copy_minimal_tuple(MinimalTuple mtup)
{
	MinimalTuple result;

	result = (MinimalTuple) palloc(mtup->t_len);
	memcpy(result, mtup, mtup->t_len);
	return result;
}

/*
 * heap_tuple_from_minimal_tuple
 *		create a HeapTuple by copying from a MinimalTuple;
 *		system columns are filled with zeroes
 *
 * The result is allocated in the current memory context.
 * The HeapTuple struct, tuple header, and tuple data are all allocated
 * as a single palloc() block.
 */
HeapTuple
heap_tuple_from_minimal_tuple(MinimalTuple mtup)
{
	HeapTuple	result;
	uint32		len = mtup->t_len + MINIMAL_TUPLE_OFFSET;

	result = (HeapTuple) palloc(HEAPTUPLESIZE + len);
	result->t_len = len;
	ItemPointerSetInvalid(&(result->t_self));
	result->t_tableOid = InvalidOid;
	result->t_data = (HeapTupleHeader) ((char *) result + HEAPTUPLESIZE);
	memcpy((char *) result->t_data + MINIMAL_TUPLE_OFFSET, mtup, mtup->t_len);
	memset(result->t_data, 0, offsetof(HeapTupleHeaderData, t_infomask2));
	return result;
}

/*
 * minimal_tuple_from_heap_tuple
 *		create a MinimalTuple by copying from a HeapTuple
 *
 * The result is allocated in the current memory context.
 */
MinimalTuple
minimal_tuple_from_heap_tuple(HeapTuple htup)
{
	MinimalTuple result;
	uint32		len;

	Assert(htup->t_len > MINIMAL_TUPLE_OFFSET);
	len = htup->t_len - MINIMAL_TUPLE_OFFSET;
	result = (MinimalTuple) palloc(len);
	memcpy(result, (char *) htup->t_data + MINIMAL_TUPLE_OFFSET, len);
	result->t_len = len;
	return result;
}


/* ----------------
 *		heap_addheader
 *
 * This routine forms a HeapTuple by copying the given structure (tuple
 * data) and adding a generic header.  Note that the tuple data is
 * presumed to contain no null fields and no varlena fields.
 *
 * This routine is really only useful for certain system tables that are
 * known to be fixed-width and null-free.  Currently it is only used for
 * pg_attribute tuples.
 * ----------------
 */
HeapTuple
heap_addheader(int natts,		/* max domain index */
			   bool withoid,	/* reserve space for oid */
			   Size structlen,	/* its length */
			   void *structure) /* pointer to the struct */
{
	HeapTuple	tuple;
	HeapTupleHeader td;
	Size		len;
	int			hoff;

	AssertArg(natts > 0);

	/* header needs no null bitmap */
	hoff = offsetof(HeapTupleHeaderData, t_bits);
	if (withoid)
		hoff += sizeof(Oid);
	hoff = MAXALIGN(hoff);
	len = hoff + structlen;

	tuple = (HeapTuple) palloc0(HEAPTUPLESIZE + len);
	tuple->t_data = td = (HeapTupleHeader) ((char *) tuple + HEAPTUPLESIZE);

	tuple->t_len = len;
	ItemPointerSetInvalid(&(tuple->t_self));
	tuple->t_tableOid = InvalidOid;

	/* we don't bother to fill the Datum fields */

	HeapTupleHeaderSetNatts(td, natts);
	td->t_hoff = hoff;

	if (withoid)				/* else leave infomask = 0 */
		td->t_infomask = HEAP_HASOID;

	memcpy((char *) td + hoff, structure, structlen);

	return tuple;
}