plancat.c

关系型数据库 Postgresql 6.5.2

Cost
restriction_selectivity(Oid functionObjectId,
						Oid operatorObjectId,
						Oid relationObjectId,
						AttrNumber attributeNumber,
						char *constValue,
						int32 constFlag)
{
	float64		result;

	result = (float64) fmgr(functionObjectId,
							(char *) operatorObjectId,
							(char *) relationObjectId,
							(char *) (int) attributeNumber,
							(char *) constValue,
							(char *) constFlag,
							NULL);
	if (!PointerIsValid(result))
		elog(ERROR, "RestrictionClauseSelectivity: bad pointer");

	if (*result < 0.0 || *result > 1.0)
		elog(ERROR, "RestrictionClauseSelectivity: bad value %lf",
			 *result);

	return (Cost) *result;
}

/*
 * join_selectivity
 *	  Similarly, this routine is merged with JoinClauseSelectivity in
 *	  plancat.c
 *
 *	  Returns the selectivity of an operator, given the join clause
 *	  information.
 *
 * XXX The assumption in the selectivity procedures is that if the
 *		relation OIDs or attribute numbers are -1, then the clause
 *		isn't of the form (op var var).
 */
Cost
join_selectivity(Oid functionObjectId,
				 Oid operatorObjectId,
				 Oid relationObjectId1,
				 AttrNumber attributeNumber1,
				 Oid relationObjectId2,
				 AttrNumber attributeNumber2)
{
	float64		result;

	result = (float64) fmgr(functionObjectId,
							(char *) operatorObjectId,
							(char *) relationObjectId1,
							(char *) (int) attributeNumber1,
							(char *) relationObjectId2,
							(char *) (int) attributeNumber2,
							NULL);
	if (!PointerIsValid(result))
		elog(ERROR, "JoinClauseSelectivity: bad pointer");

	if (*result < 0.0 || *result > 1.0)
		elog(ERROR, "JoinClauseSelectivity: bad value %lf",
			 *result);

	return (Cost) *result;
}

/*
 * find_all_inheritors
 *
 * Returns a LISP list containing the OIDs of all relations which
 * inherits from the relation with OID 'inhparent'.
 */
List *
find_inheritance_children(Oid inhparent)
{
	static ScanKeyData key[1] = {
		{0, Anum_pg_inherits_inhparent, F_OIDEQ}
	};

	HeapTuple	inheritsTuple;
	Relation	relation;
	HeapScanDesc scan;
	List	   *list = NIL;
	Oid			inhrelid;

	fmgr_info(F_OIDEQ, &key[0].sk_func);
	key[0].sk_nargs = key[0].sk_func.fn_nargs;

	key[0].sk_argument = ObjectIdGetDatum((Oid) inhparent);
	relation = heap_openr(InheritsRelationName);
	scan = heap_beginscan(relation, 0, SnapshotNow, 1, key);
	while (HeapTupleIsValid(inheritsTuple = heap_getnext(scan, 0)))
	{
		inhrelid = ((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhrel;
		list = lappendi(list, inhrelid);
	}
	heap_endscan(scan);
	heap_close(relation);
	return list;
}

#ifdef NOT_USED
/*
 * VersionGetParents
 *
 * Returns a LISP list containing the OIDs of all relations which are
 * base relations of the relation with OID 'verrelid'.
 */
List *
VersionGetParents(Oid verrelid)
{
	static ScanKeyData key[1] = {
		{0, Anum_pg_version_verrelid, F_OIDEQ}
	};

	HeapTuple	versionTuple;
	Relation	relation;
	HeapScanDesc scan;
	Oid			verbaseid;
	List	   *list = NIL;

	fmgr_info(F_OIDEQ, &key[0].sk_func);
	key[0].sk_nargs = key[0].sk_func.fn_nargs;
	relation = heap_openr(VersionRelationName);
	key[0].sk_argument = ObjectIdGetDatum(verrelid);
	scan = heap_beginscan(relation, 0, SnapshotNow, 1, key);
	while (HeapTupleIsValid(versionTuple = heap_getnext(scan, 0)))
	{
		verbaseid = ((Form_pg_version)
					 GETSTRUCT(versionTuple))->verbaseid;

		list = lconsi(verbaseid, list);

		key[0].sk_argument = ObjectIdGetDatum(verbaseid);
		heap_rescan(scan, 0, key);
	}
	heap_endscan(scan);
	heap_close(relation);
	return list;
}

#endif


/*****************************************************************************
 *
 *****************************************************************************/

/*
 * IdexSelectivity
 *
 *	  Retrieves the 'amopnpages' and 'amopselect' parameters for each
 *	  AM operator when a given index (specified by 'indexrelid') is used.
 *	  These two parameters are returned by copying them to into an array of
 *	  floats.
 *
 *	  Assumption: the attribute numbers and operator ObjectIds are in order
 *	  WRT to each other (otherwise, you have no way of knowing which
 *	  AM operator class or attribute number corresponds to which operator.
 *
 * 'varAttributeNumbers' contains attribute numbers for variables
 * 'constValues' contains the constant values
 * 'constFlags' describes how to treat the constants in each clause
 * 'nIndexKeys' describes how many keys the index actually has
 *
 * Returns 'selectivityInfo' filled with the sum of all pages touched
 * and the product of each clause's selectivity.
 *
 */
static void
IndexSelectivity(Oid indexrelid,
				 Oid indrelid,
				 int32 nIndexKeys,
				 Oid *AccessMethodOperatorClasses,		/* XXX not used? */
				 Oid *operatorObjectIds,
				 int32 *varAttributeNumbers,
				 char **constValues,
				 int32 *constFlags,
				 float *idxPages,
				 float *idxSelec)
{
	int			i,
				n;
	HeapTuple	indexTuple,
				amopTuple,
				indRel;
	Form_pg_index index;
	Form_pg_amop amop;
	Oid			indclass;
	float64data npages,
				select;
	float64		amopnpages,
				amopselect;
	Oid			relam;
	bool		nphack = false;
	float64data fattr_select = 1.0;

	indRel = SearchSysCacheTuple(RELOID,
								 ObjectIdGetDatum(indexrelid),
								 0, 0, 0);
	if (!HeapTupleIsValid(indRel))
		elog(ERROR, "IndexSelectivity: index %u not found",
			 indexrelid);
	relam = ((Form_pg_class) GETSTRUCT(indRel))->relam;

	indexTuple = SearchSysCacheTuple(INDEXRELID,
									 ObjectIdGetDatum(indexrelid),
									 0, 0, 0);
	if (!HeapTupleIsValid(indexTuple))
		elog(ERROR, "IndexSelectivity: index %u not found",
			 indexrelid);
	index = (Form_pg_index) GETSTRUCT(indexTuple);

	/*
	 * Hack for non-functional btree npages estimation: npages =
	 * index_pages * selectivity_of_1st_attr_clause(s) - vadim 04/24/97
	 */
	if (relam == BTREE_AM_OID &&
		varAttributeNumbers[0] != InvalidAttrNumber)
		nphack = true;

	npages = 0.0;
	select = 1.0;
	for (n = 0; n < nIndexKeys; ++n)
	{

		/*
		 * Find the AM class for this key.
		 *
		 * If the first attribute number is invalid then we have a functional
		 * index, and AM class is the first one defined since functional
		 * indices have exactly one key.
		 */
		indclass = (varAttributeNumbers[0] == InvalidAttrNumber) ?
			index->indclass[0] : InvalidOid;
		i = 0;
		while ((i < nIndexKeys) && (indclass == InvalidOid))
		{
			if (varAttributeNumbers[n] == index->indkey[i])
			{
				indclass = index->indclass[i];
				break;
			}
			i++;
		}
		if (!OidIsValid(indclass))
		{

			/*
			 * Presumably this means that we are using a functional index
			 * clause and so had no variable to match to the index key ...
			 * if not we are in trouble.
			 */
			elog(NOTICE, "IndexSelectivity: no key %d in index %u",
				 varAttributeNumbers[n], indexrelid);
			continue;
		}

		amopTuple = SearchSysCacheTuple(AMOPOPID,
										ObjectIdGetDatum(indclass),
								  ObjectIdGetDatum(operatorObjectIds[n]),
										ObjectIdGetDatum(relam),
										0);
		if (!HeapTupleIsValid(amopTuple))
			elog(ERROR, "IndexSelectivity: no amop %u %u",
				 indclass, operatorObjectIds[n]);
		amop = (Form_pg_amop) GETSTRUCT(amopTuple);

		if (!nphack)
		{
			amopnpages = (float64) fmgr(amop->amopnpages,
										(char *) operatorObjectIds[n],
										(char *) indrelid,
										(char *) varAttributeNumbers[n],
										(char *) constValues[n],
										(char *) constFlags[n],
										(char *) nIndexKeys,
										(char *) indexrelid);
#ifdef NOT_USED
/*
 * So cool guys! Npages for x > 10 and x < 20 is twice as
 * npages for x > 10!	- vadim 04/09/97
 */
			npages += PointerIsValid(amopnpages) ? *amopnpages : 0.0;
			if ((i = npages) < npages)	/* ceil(npages)? */
				npages += 1.0;
#endif
			npages += PointerIsValid(amopnpages) ? *amopnpages : 0.0;
		}

		amopselect = (float64) fmgr(amop->amopselect,
									(char *) operatorObjectIds[n],
									(char *) indrelid,
									(char *) varAttributeNumbers[n],
									(char *) constValues[n],
									(char *) constFlags[n],
									(char *) nIndexKeys,
									(char *) indexrelid);

		if (nphack && varAttributeNumbers[n] == index->indkey[0])
			fattr_select *= PointerIsValid(amopselect) ? *amopselect : 1.0;

		select *= PointerIsValid(amopselect) ? *amopselect : 1.0;
	}

	/*
	 * Estimation of npages below is hack of course, but it's better than
	 * it was before.		- vadim 04/09/97
	 */
	if (nphack)
	{
		npages = fattr_select * ((Form_pg_class) GETSTRUCT(indRel))->relpages;
		*idxPages = ceil((double) npages);
	}
	else
	{
		if (nIndexKeys > 1)
			npages = npages / (1.0 + nIndexKeys);
		*idxPages = ceil((double) (npages / nIndexKeys));
	}
	*idxSelec = select;
}