heaptuple.c

postgresql8.3.4源码,开源数据库

 *		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.
 *		Also see nocache_index_getattr, which is the same code for index
 *		tuples.
 * ----------------
 */
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 data part of tuple */
	bits8	   *bp = tup->t_bits;		/* ptr to null bitmap in tuple */
	bool		slow = false;	/* do we have to walk attrs? */
	int			off;			/* current offset within data */

	(void) isnull;				/* not used */

	/* ----------------
	 *	 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.
	 * ----------------
	 */

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

	if (isnull)
		*isnull = false;
#endif

	attnum--;

	if (HeapTupleNoNulls(tuple))
	{
#ifdef IN_MACRO
/* This is handled in the macro */
		if (att[attnum]->attcacheoff >= 0)
		{
			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;

	if (!slow)
	{
		/*
		 * If we get here, there are no nulls up to and including the target
		 * attribute.  If we have a cached offset, we can use it.
		 */
		if (att[attnum]->attcacheoff >= 0)
		{
			return fetchatt(att[attnum],
							tp + att[attnum]->attcacheoff);
		}

		/*
		 * Otherwise, check for non-fixed-length attrs up to and including
		 * target.	If there aren't any, it's safe to cheaply initialize the
		 * cached offsets for these attrs.
		 */
		if (HeapTupleHasVarWidth(tuple))
		{
			int			j;

			for (j = 0; j <= attnum; j++)
			{
				if (att[j]->attlen <= 0)
				{
					slow = true;
					break;
				}
			}
		}
	}

	if (!slow)
	{
		int			natts = tupleDesc->natts;
		int			j = 1;

		/*
		 * If we get here, we have a tuple with no nulls or var-widths up to
		 * and including the target attribute, so we can use the cached offset
		 * ... only we don't have it yet, or we'd not have got here.  Since
		 * it's cheap to compute offsets for fixed-width columns, we take the
		 * opportunity to initialize the cached offsets for *all* the leading
		 * fixed-width columns, in hope of avoiding future visits to this
		 * routine.
		 */
		att[0]->attcacheoff = 0;

		/* we might have set some offsets in the slow path previously */
		while (j < natts && att[j]->attcacheoff > 0)
			j++;

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

		for (; j < natts; j++)
		{
			if (att[j]->attlen <= 0)
				break;

			off = att_align_nominal(off, att[j]->attalign);

			att[j]->attcacheoff = off;

			off += att[j]->attlen;
		}

		Assert(j > attnum);

		off = att[attnum]->attcacheoff;
	}
	else
	{
		bool		usecache = true;
		int			i;

		/*
		 * Now we know that we have to walk the tuple CAREFULLY.  But we still
		 * might be able to cache some offsets for next time.
		 *
		 * 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 reach either a null or a var-width attribute.
		 */
		off = 0;
		for (i = 0;; i++)		/* loop exit is at "break" */
		{
			if (HeapTupleHasNulls(tuple) && att_isnull(i, bp))
			{
				usecache = false;
				continue;		/* this cannot be the target att */
			}

			/* If we know the next offset, we can skip the rest */
			if (usecache && att[i]->attcacheoff >= 0)
				off = att[i]->attcacheoff;
			else if (att[i]->attlen == -1)
			{
				/*
				 * We can only cache the offset for a varlena attribute if the
				 * offset is already suitably aligned, so that there would be
				 * no pad bytes in any case: then the offset will be valid for
				 * either an aligned or unaligned value.
				 */
				if (usecache &&
					off == att_align_nominal(off, att[i]->attalign))
					att[i]->attcacheoff = off;
				else
				{
					off = att_align_pointer(off, att[i]->attalign, -1,
											tp + off);
					usecache = false;
				}
			}
			else
			{
				/* not varlena, so safe to use att_align_nominal */
				off = att_align_nominal(off, att[i]->attalign);

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

			if (i == attnum)
				break;

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

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

	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 MaxTransactionIdAttributeNumber:
			result = TransactionIdGetDatum(HeapTupleHeaderGetXmax(tup->t_data));
			break;
		case MinCommandIdAttributeNumber:
		case MaxCommandIdAttributeNumber:

			/*
			 * cmin and cmax are now both aliases for the same field, which
			 * can in fact also be a combo command id.	XXX perhaps we should
			 * return the "real" cmin or cmax if possible, that is if we are
			 * inside the originating transaction?
			 */
			result = CommandIdGetDatum(HeapTupleHeaderGetRawCommandId(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_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
 *
 * Note that after calling this function, the "dest" HeapTuple will not be
 * allocated as a single palloc() block (unlike with heap_copytuple()).
 * ----------------
 */
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_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 */
	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(HeapTupleHeaderData, 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.	Note that the tuple body and
	 * HeapTupleData management structure are allocated in one chunk.
	 */
	tuple = (HeapTuple) palloc0(HEAPTUPLESIZE + len);
	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);

	HeapTupleHeaderSetNatts(td, 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,
					data_len,
					&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 */
	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 (nulls[i] != ' ')
			hasnull = true;
		else if (att[i]->attlen == -1 &&
				 att[i]->attalign == 'd' &&