lsyscache.c

/*-------------------------------------------------------------------------
 *
 * lsyscache.c
 *	  Convenience routines for common queries in the system catalog cache.
 *
 * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/utils/cache/lsyscache.c,v 1.166 2010/01/04 02:44:40 tgl Exp $
 *
 * NOTES
 *	  Eventually, the index information should go through here, too.
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/hash.h"
#include "access/nbtree.h"
#include "bootstrap/bootstrap.h"
#include "catalog/pg_amop.h"
#include "catalog/pg_amproc.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_statistic.h"
#include "catalog/pg_type.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/datum.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"

/* Hook for plugins to get control in get_attavgwidth() */
get_attavgwidth_hook_type get_attavgwidth_hook = NULL;


/*				---------- AMOP CACHES ----------						 */

/*
 * op_in_opfamily
 *
 *		Return t iff operator 'opno' is in operator family 'opfamily'.
 */
bool
op_in_opfamily(Oid opno, Oid opfamily)
{
	return SearchSysCacheExists(AMOPOPID,
								ObjectIdGetDatum(opno),
								ObjectIdGetDatum(opfamily),
								0, 0);
}

/*
 * get_op_opfamily_strategy
 *
 *		Get the operator's strategy number within the specified opfamily,
 *		or 0 if it's not a member of the opfamily.
 */
int
get_op_opfamily_strategy(Oid opno, Oid opfamily)
{
	HeapTuple	tp;
	Form_pg_amop amop_tup;
	int			result;

	tp = SearchSysCache(AMOPOPID,
						ObjectIdGetDatum(opno),
						ObjectIdGetDatum(opfamily),
						0, 0);
	if (!HeapTupleIsValid(tp))
		return 0;
	amop_tup = (Form_pg_amop) GETSTRUCT(tp);
	result = amop_tup->amopstrategy;
	ReleaseSysCache(tp);
	return result;
}

/*
 * get_op_opfamily_properties
 *
 *		Get the operator's strategy number and declared input data types
 *		within the specified opfamily.
 *
 * Caller should already have verified that opno is a member of opfamily,
 * therefore we raise an error if the tuple is not found.
 */
void
get_op_opfamily_properties(Oid opno, Oid opfamily,
						   int *strategy,
						   Oid *lefttype,
						   Oid *righttype)
{
	HeapTuple	tp;
	Form_pg_amop amop_tup;

	tp = SearchSysCache(AMOPOPID,
						ObjectIdGetDatum(opno),
						ObjectIdGetDatum(opfamily),
						0, 0);
	if (!HeapTupleIsValid(tp))
		elog(ERROR, "operator %u is not a member of opfamily %u",
			 opno, opfamily);
	amop_tup = (Form_pg_amop) GETSTRUCT(tp);
	*strategy = amop_tup->amopstrategy;
	*lefttype = amop_tup->amoplefttype;
	*righttype = amop_tup->amoprighttype;
	ReleaseSysCache(tp);
}

/*
 * get_opfamily_member
 *		Get the OID of the operator that implements the specified strategy
 *		with the specified datatypes for the specified opfamily.
 *
 * Returns InvalidOid if there is no pg_amop entry for the given keys.
 */
Oid
get_opfamily_member(Oid opfamily, Oid lefttype, Oid righttype,
					int16 strategy)
{
	HeapTuple	tp;
	Form_pg_amop amop_tup;
	Oid			result;

	tp = SearchSysCache(AMOPSTRATEGY,
						ObjectIdGetDatum(opfamily),
						ObjectIdGetDatum(lefttype),
						ObjectIdGetDatum(righttype),
						Int16GetDatum(strategy));
	if (!HeapTupleIsValid(tp))
		return InvalidOid;
	amop_tup = (Form_pg_amop) GETSTRUCT(tp);
	result = amop_tup->amopopr;
	ReleaseSysCache(tp);
	return result;
}

/*
 * get_ordering_op_properties
 *		Given the OID of an ordering operator (a btree "<" or ">" operator),
 *		determine its opfamily, its declared input datatype, and its
 *		strategy number (BTLessStrategyNumber or BTGreaterStrategyNumber).
 *
 * Returns TRUE if successful, FALSE if no matching pg_amop entry exists.
 * (This indicates that the operator is not a valid ordering operator.)
 *
 * Note: the operator could be registered in multiple families, for example
 * if someone were to build a "reverse sort" opfamily.	This would result in
 * uncertainty as to whether "ORDER BY USING op" would default to NULLS FIRST
 * or NULLS LAST, as well as inefficient planning due to failure to match up
 * pathkeys that should be the same.  So we want a determinate result here.
 * Because of the way the syscache search works, we'll use the interpretation
 * associated with the opfamily with smallest OID, which is probably
 * determinate enough.	Since there is no longer any particularly good reason
 * to build reverse-sort opfamilies, it doesn't seem worth expending any
 * additional effort on ensuring consistency.
 */
bool
get_ordering_op_properties(Oid opno,
						   Oid *opfamily, Oid *opcintype, int16 *strategy)
{
	bool		result = false;
	CatCList   *catlist;
	int			i;

	/* ensure outputs are initialized on failure */
	*opfamily = InvalidOid;
	*opcintype = InvalidOid;
	*strategy = 0;

	/*
	 * Search pg_amop to see if the target operator is registered as the "<"
	 * or ">" operator of any btree opfamily.
	 */
	catlist = SearchSysCacheList(AMOPOPID, 1,
								 ObjectIdGetDatum(opno),
								 0, 0, 0);

	for (i = 0; i < catlist->n_members; i++)
	{
		HeapTuple	tuple = &catlist->members[i]->tuple;
		Form_pg_amop aform = (Form_pg_amop) GETSTRUCT(tuple);

		/* must be btree */
		if (aform->amopmethod != BTREE_AM_OID)
			continue;

		if (aform->amopstrategy == BTLessStrategyNumber ||
			aform->amopstrategy == BTGreaterStrategyNumber)
		{
			/* Found it ... should have consistent input types */
			if (aform->amoplefttype == aform->amoprighttype)
			{
				/* Found a suitable opfamily, return info */
				*opfamily = aform->amopfamily;