lsyscache.c

/*-------------------------------------------------------------------------
 *
 * lsyscache.c
 *	  Convenience routines for common queries in the system catalog cache.
 *
 * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v 1.108 2003/10/04 18:22:59 tgl Exp $
 *
 * NOTES
 *	  Eventually, the index information should go through here, too.
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
#include "miscadmin.h"

#include "access/hash.h"
#include "access/tupmacs.h"
#include "catalog/pg_amop.h"
#include "catalog/pg_amproc.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_shadow.h"
#include "catalog/pg_statistic.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/catcache.h"
#include "utils/datum.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"


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

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

/*
 * op_requires_recheck
 *
 *		Return t if operator 'opno' requires a recheck when used as a
 *		member of opclass 'opclass' (ie, this opclass is lossy for this
 *		operator).
 *
 * Caller should already have verified that opno is a member of opclass,
 * therefore we raise an error if the tuple is not found.
 */
bool
op_requires_recheck(Oid opno, Oid opclass)
{
	HeapTuple	tp;
	Form_pg_amop amop_tup;
	bool		result;

	tp = SearchSysCache(AMOPOPID,
						ObjectIdGetDatum(opno),
						ObjectIdGetDatum(opclass),
						0, 0);
	if (!HeapTupleIsValid(tp))
		elog(ERROR, "operator %u is not a member of opclass %u",
			 opno, opclass);
	amop_tup = (Form_pg_amop) GETSTRUCT(tp);

	result = amop_tup->amopreqcheck;
	ReleaseSysCache(tp);
	return result;
}

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

	tp = SearchSysCache(AMOPSTRATEGY,
						ObjectIdGetDatum(opclass),
						Int16GetDatum(strategy),
						0, 0);
	if (!HeapTupleIsValid(tp))
		return InvalidOid;
	amop_tup = (Form_pg_amop) GETSTRUCT(tp);
	result = amop_tup->amopopr;
	ReleaseSysCache(tp);
	return result;
}

/*
 * get_op_hash_function
 *		Get the OID of the datatype-specific hash function associated with
 *		a hashable equality operator.
 *
 * Returns InvalidOid if no hash function can be found.  (This indicates
 * that the operator should not have been marked oprcanhash.)
 */
Oid
get_op_hash_function(Oid opno)
{
	CatCList   *catlist;
	int			i;
	Oid			opclass = InvalidOid;

	/*
	 * Search pg_amop to see if the target operator is registered as the
	 * "=" operator of any hash opclass.  If the operator is registered in
	 * multiple opclasses, assume we can use the associated hash function
	 * from any one.
	 */
	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);

		if (aform->amopstrategy == HTEqualStrategyNumber &&
			opclass_is_hash(aform->amopclaid))
		{
			opclass = aform->amopclaid;
			break;
		}
	}

	ReleaseSysCacheList(catlist);

	if (OidIsValid(opclass))
	{
		/* Found a suitable opclass, get its hash support function */
		return get_opclass_proc(opclass, HASHPROC);
	}

	/* Didn't find a match... */
	return InvalidOid;
}


/*				---------- AMPROC CACHES ----------						 */

/*
 * get_opclass_proc
 *		Get the OID of the specified support function
 *		for the specified opclass.
 *
 * Returns InvalidOid if there is no pg_amproc entry for the given keys.
 */
Oid
get_opclass_proc(Oid opclass, int16 procnum)
{
	HeapTuple	tp;
	Form_pg_amproc amproc_tup;
	RegProcedure result;

	tp = SearchSysCache(AMPROCNUM,
						ObjectIdGetDatum(opclass),
						Int16GetDatum(procnum),
						0, 0);
	if (!HeapTupleIsValid(tp))
		return InvalidOid;
	amproc_tup = (Form_pg_amproc) GETSTRUCT(tp);
	result = amproc_tup->amproc;
	ReleaseSysCache(tp);
	return result;
}


/*				---------- ATTRIBUTE CACHES ----------					 */

/*
 * get_attname
 *		Given the relation id and the attribute number,
 *		return the "attname" field from the attribute relation.
 *
 * Note: returns a palloc'd copy of the string, or NULL if no such attribute.
 */