heaptuple.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

			}

			/* If we know the next offset, we can skip the alignment calc */
			if (usecache && att[i]->attcacheoff != -1)
				off = att[i]->attcacheoff;
			else
			{
				off = att_align(off, att[i]->attalign);

				if (usecache)
					att[i]->attcacheoff = off;
			}

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

			if (usecache && att[i]->attlen <= 0)
				usecache = false;
		}

		off = att_align(off, att[attnum]->attalign);

		return fetchatt(att[attnum], tp + off);
	}
}

/* ----------------
 *		heap_getsysattr
 *
 *		Fetch the value of a system attribute for a tuple.
 *
 * This is a support routine for the heap_getattr macro.  The macro
 * has already determined that the attnum refers to a system attribute.
 * ----------------
 */
Datum
heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
{
	Datum		result;

	Assert(tup);

	/* Currently, no sys attribute ever reads as NULL. */
	if (isnull)
		*isnull = false;

	switch (attnum)
	{
		case SelfItemPointerAttributeNumber:
			/* pass-by-reference datatype */
			result = PointerGetDatum(&(tup->t_self));
			break;
		case ObjectIdAttributeNumber:
			result = ObjectIdGetDatum(HeapTupleGetOid(tup));
			break;
		case MinTransactionIdAttributeNumber:
			result = TransactionIdGetDatum(HeapTupleHeaderGetXmin(tup->t_data));
			break;
		case MinCommandIdAttributeNumber:
			result = CommandIdGetDatum(HeapTupleHeaderGetCmin(tup->t_data));
			break;
		case MaxTransactionIdAttributeNumber:
			result = TransactionIdGetDatum(HeapTupleHeaderGetXmax(tup->t_data));
			break;
		case MaxCommandIdAttributeNumber:
			result = CommandIdGetDatum(HeapTupleHeaderGetCmax(tup->t_data));
			break;
		case TableOidAttributeNumber:
			result = ObjectIdGetDatum(tup->t_tableOid);
			break;
		default:
			elog(ERROR, "invalid attnum: %d", attnum);
			result = 0;			/* keep compiler quiet */
			break;
	}
	return result;
}

/* ----------------
 *		heap_copytuple
 *
 *		returns a copy of an entire tuple
 *
 * The HeapTuple struct, tuple header, and tuple data are all allocated
 * as a single palloc() block.
 * ----------------
 */
HeapTuple
heap_copytuple(HeapTuple tuple)
{
	HeapTuple	newTuple;

	if (!HeapTupleIsValid(tuple) || tuple->t_data == NULL)
		return NULL;

	newTuple = (HeapTuple) palloc(HEAPTUPLESIZE + tuple->t_len);
	newTuple->t_len = tuple->t_len;
	newTuple->t_self = tuple->t_self;
	newTuple->t_tableOid = tuple->t_tableOid;
	newTuple->t_datamcxt = CurrentMemoryContext;
	newTuple->t_data = (HeapTupleHeader) ((char *) newTuple + HEAPTUPLESIZE);
	memcpy((char *) newTuple->t_data, (char *) tuple->t_data, tuple->t_len);
	return newTuple;
}

/* ----------------
 *		heap_copytuple_with_tuple
 *
 *		copy a tuple into a caller-supplied HeapTuple management struct
 * ----------------
 */
void
heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest)
{
	if (!HeapTupleIsValid(src) || src->t_data == NULL)
	{
		dest->t_data = NULL;
		return;
	}

	dest->t_len = src->t_len;
	dest->t_self = src->t_self;
	dest->t_tableOid = src->t_tableOid;
	dest->t_datamcxt = CurrentMemoryContext;
	dest->t_data = (HeapTupleHeader) palloc(src->t_len);
	memcpy((char *) dest->t_data, (char *) src->t_data, src->t_len);
}

/*
 * heap_form_tuple
 *		construct a tuple from the given values[] and isnull[] arrays,
 *		which are of the length indicated by tupleDescriptor->natts
 *
 * The result is allocated in the current memory context.
 */
HeapTuple
heap_form_tuple(TupleDesc tupleDescriptor,
				Datum *values,
				bool *isnull)
{
	HeapTuple	tuple;			/* return tuple */
	HeapTupleHeader td;			/* tuple data */
	unsigned long 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(HeapTupleHeaderData, t_bits);

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

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

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

	len += heap_compute_data_size(tupleDescriptor, values, isnull);

	/*
	 * Allocate and zero the space needed.	Note that the tuple body and
	 * HeapTupleData management structure are allocated in one chunk.
	 */
	tuple = (HeapTuple) palloc0(HEAPTUPLESIZE + len);
	tuple->t_datamcxt = CurrentMemoryContext;
	tuple->t_data = td = (HeapTupleHeader) ((char *) tuple + HEAPTUPLESIZE);

	/*
	 * And fill in the information.  Note we fill the Datum fields even though
	 * this tuple may never become a Datum.
	 */
	tuple->t_len = len;
	ItemPointerSetInvalid(&(tuple->t_self));
	tuple->t_tableOid = InvalidOid;

	HeapTupleHeaderSetDatumLength(td, len);
	HeapTupleHeaderSetTypeId(td, tupleDescriptor->tdtypeid);
	HeapTupleHeaderSetTypMod(td, tupleDescriptor->tdtypmod);

	td->t_natts = numberOfAttributes;
	td->t_hoff = hoff;

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

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

	return tuple;
}

/* ----------------
 *		heap_formtuple
 *
 *		construct a tuple from the given values[] and nulls[] arrays
 *
 *		Null attributes are indicated by a 'n' in the appropriate byte
 *		of nulls[]. Non-null attributes are indicated by a ' ' (space).
 *
 * OLD API with char 'n'/' ' convention for indicating nulls
 * ----------------
 */
HeapTuple
heap_formtuple(TupleDesc tupleDescriptor,
			   Datum *values,
			   char *nulls)
{
	HeapTuple	tuple;			/* return tuple */
	HeapTupleHeader td;			/* tuple data */
	unsigned long 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 (nulls[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(HeapTupleHeaderData, t_bits);

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

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

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

	len += ComputeDataSize(tupleDescriptor, values, nulls);

	/*
	 * Allocate and zero the space needed.	Note that the tuple body and
	 * HeapTupleData management structure are allocated in one chunk.
	 */
	tuple = (HeapTuple) palloc0(HEAPTUPLESIZE + len);
	tuple->t_datamcxt = CurrentMemoryContext;
	tuple->t_data = td = (HeapTupleHeader) ((char *) tuple + HEAPTUPLESIZE);

	/*
	 * And fill in the information.  Note we fill the Datum fields even though
	 * this tuple may never become a Datum.
	 */
	tuple->t_len = len;
	ItemPointerSetInvalid(&(tuple->t_self));
	tuple->t_tableOid = InvalidOid;

	HeapTupleHeaderSetDatumLength(td, len);
	HeapTupleHeaderSetTypeId(td, tupleDescriptor->tdtypeid);
	HeapTupleHeaderSetTypMod(td, tupleDescriptor->tdtypmod);

	td->t_natts = numberOfAttributes;
	td->t_hoff = hoff;

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

	DataFill((char *) td + hoff,
			 tupleDescriptor,
			 values,
			 nulls,
			 &td->t_infomask,
			 (hasnull ? td->t_bits : NULL));

	return tuple;
}

/*
 * heap_modify_tuple
 *		form a new tuple from an old tuple and a set of replacement values.
 *
 * The replValues, replIsnull, and doReplace arrays must be of the length
 * indicated by tupleDesc->natts.  The new tuple is constructed using the data
 * from replValues/replIsnull at columns where doReplace is true, and using
 * the data from the old tuple at columns where doReplace is false.
 *
 * The result is allocated in the current memory context.
 */
HeapTuple
heap_modify_tuple(HeapTuple tuple,
				  TupleDesc tupleDesc,
				  Datum *replValues,
				  bool *replIsnull,
				  bool *doReplace)
{
	int			numberOfAttributes = tupleDesc->natts;
	int			attoff;
	Datum	   *values;
	bool	   *isnull;
	HeapTuple	newTuple;

	/*
	 * allocate and fill values and isnull arrays from either the tuple or the
	 * repl information, as appropriate.
	 *
	 * NOTE: it's debatable whether to use heap_deform_tuple() here or just
	 * heap_getattr() only the non-replaced colums.  The latter could win if
	 * there are many replaced columns and few non-replaced ones. However,
	 * heap_deform_tuple costs only O(N) while the heap_getattr way would cost
	 * O(N^2) if there are many non-replaced columns, so it seems better to
	 * err on the side of linear cost.
	 */
	values = (Datum *) palloc(numberOfAttributes * sizeof(Datum));
	isnull = (bool *) palloc(numberOfAttributes * sizeof(bool));

	heap_deform_tuple(tuple, tupleDesc, values, isnull);

	for (attoff = 0; attoff < numberOfAttributes; attoff++)
	{
		if (doReplace[attoff])
		{
			values[attoff] = replValues[attoff];
			isnull[attoff] = replIsnull[attoff];
		}
	}

	/*
	 * create a new tuple from the values and isnull arrays
	 */
	newTuple = heap_form_tuple(tupleDesc, values, isnull);

	pfree(values);
	pfree(isnull);

	/*
	 * copy the identification info of the old tuple: t_ctid, t_self, and OID
	 * (if any)
	 */
	newTuple->t_data->t_ctid = tuple->t_data->t_ctid;
	newTuple->t_self = tuple->t_self;
	newTuple->t_tableOid = tuple->t_tableOid;
	if (tupleDesc->tdhasoid)
		HeapTupleSetOid(newTuple, HeapTupleGetOid(tuple));

	return newTuple;
}

/* ----------------
 *		heap_modifytuple
 *
 *		forms a new tuple from an old tuple and a set of replacement values.
 *		returns a new palloc'ed tuple.
 *
 * OLD API with char 'n'/' ' convention for indicating nulls, and
 * char 'r'/' ' convention for indicating whether to replace columns.
 * ----------------
 */
HeapTuple
heap_modifytuple(HeapTuple tuple,
				 TupleDesc tupleDesc,
				 Datum *replValues,
				 char *replNulls,
				 char *replActions)
{
	int			numberOfAttributes = tupleDesc->natts;
	int			attoff;
	Datum	   *values;
	char	   *nulls;
	HeapTuple	newTuple;

	/*
	 * allocate and fill values and nulls arrays from either the tuple or the
	 * repl information, as appropriate.
	 *
	 * NOTE: it's debatable whether to use heap_deformtuple() here or just
	 * heap_getattr() only the non-replaced colums.  The latter could win if
	 * there are many replaced columns and few non-replaced ones. However,
	 * heap_deformtuple costs only O(N) while the heap_getattr way would cost
	 * O(N^2) if there are many non-replaced columns, so it seems better to
	 * err on the side of linear cost.
	 */
	values = (Datum *) palloc(numberOfAttributes * sizeof(Datum));
	nulls = (char *) palloc(numberOfAttributes * sizeof(char));

	heap_deformtuple(tuple, tupleDesc, values, nulls);

	for (attoff = 0; attoff < numberOfAttributes; attoff++)
	{
		if (replActions[attoff] == 'r')
		{
			values[attoff] = replValues[attoff];
			nulls[attoff] = replNulls[attoff];
		}
		else if (replActions[attoff] != ' ')
			elog(ERROR, "unrecognized replace flag: %d",
				 (int) replActions[attoff]);
	}

	/*
	 * create a new tuple from the values and nulls arrays
	 */
	newTuple = heap_formtuple(tupleDesc, values, nulls);

	pfree(values);
	pfree(nulls);

	/*
	 * copy the identification info of the old tuple: t_ctid, t_self, and OID
	 * (if any)
	 */
	newTuple->t_data->t_ctid = tuple->t_data->t_ctid;
	newTuple->t_self = tuple->t_self;
	newTuple->t_tableOid = tuple->t_tableOid;
	if (tupleDesc->tdhasoid)
		HeapTupleSetOid(newTuple, HeapTupleGetOid(tuple));

	return newTuple;
}

/*
 * heap_deform_tuple
 *		Given a tuple, extract data into values/isnull arrays; this is
 *		the inverse of heap_form_tuple.
 *
 *		Storage for the values/isnull arrays is provided by the caller;
 *		it should be sized according to tupleDesc->natts not tuple->t_natts.
 *
 *		Note that for pass-by-reference datatypes, the pointer placed
 *		in the Datum will point into the given tuple.
 *
 *		When all or most of a tuple's fields need to be extracted,
 *		this routine will be significantly quicker than a loop around
 *		heap_getattr; the loop will become O(N^2) as soon as any
 *		noncacheable attribute offsets are involved.
 */
void
heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc,
				  Datum *values, bool *isnull)
{
	HeapTupleHeader tup = tuple->t_data;
	bool		hasnulls = HeapTupleHasNulls(tuple);
	Form_pg_attribute *att = tupleDesc->attrs;
	int			tdesc_natts = tupleDesc->natts;
	int			natts;			/* number of atts to extract */
	int			attnum;
	char	   *tp;				/* ptr to tuple data */
	long		off;			/* offset in tuple data */
	bits8	   *bp = tup->t_bits;		/* ptr to null bitmap in tuple */
	bool		slow = false;	/* can we use/set attcacheoff? */

	natts = tup->t_natts;

	/*
	 * In inheritance situations, it is possible that the given tuple actually
	 * has more fields than the caller is expecting.  Don't run off the end of
	 * the caller's arrays.
	 */
	natts = Min(natts, tdesc_natts);

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

	off = 0;

	for (attnum = 0; attnum < natts; attnum++)
	{