lsyscache.c

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/*-------------------------------------------------------------------------
 *
 * lsyscache.c
 *	  Convenience routines for common queries in the system catalog cache.
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/utils/cache/lsyscache.c,v 1.155 2008/01/01 19:45:53 momjian 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"


/*				---------- 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, input types, and recheck (lossy)
 *		flag 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,
						   bool *recheck)
{
	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;
	*recheck = amop_tup->amopreqcheck;
	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;
				*opcintype = aform->amoplefttype;
				*strategy = aform->amopstrategy;
				result = true;
				break;
			}
		}
	}

	ReleaseSysCacheList(catlist);

	return result;
}

/*
 * get_compare_function_for_ordering_op
 *		Get the OID of the datatype-specific btree comparison function
 *		associated with an ordering operator (a "<" or ">" operator).
 *
 * *cmpfunc receives the comparison function OID.
 * *reverse is set FALSE if the operator is "<", TRUE if it's ">"
 * (indicating the comparison result must be negated before use).
 *
 * Returns TRUE if successful, FALSE if no btree function can be found.
 * (This indicates that the operator is not a valid ordering operator.)
 */
bool
get_compare_function_for_ordering_op(Oid opno, Oid *cmpfunc, bool *reverse)
{
	Oid			opfamily;
	Oid			opcintype;
	int16		strategy;

	/* Find the operator in pg_amop */
	if (get_ordering_op_properties(opno,
								   &opfamily, &opcintype, &strategy))
	{
		/* Found a suitable opfamily, get matching support function */
		*cmpfunc = get_opfamily_proc(opfamily,
									 opcintype,
									 opcintype,
									 BTORDER_PROC);
		if (!OidIsValid(*cmpfunc))		/* should not happen */
			elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
				 BTORDER_PROC, opcintype, opcintype, opfamily);
		*reverse = (strategy == BTGreaterStrategyNumber);
		return true;
	}

	/* ensure outputs are set on failure */
	*cmpfunc = InvalidOid;
	*reverse = false;
	return false;
}

/*
 * get_equality_op_for_ordering_op
 *		Get the OID of the datatype-specific btree equality operator
 *		associated with an ordering operator (a "<" or ">" operator).
 *
 * Returns InvalidOid if no matching equality operator can be found.
 * (This indicates that the operator is not a valid ordering operator.)
 */
Oid
get_equality_op_for_ordering_op(Oid opno)
{
	Oid			result = InvalidOid;
	Oid			opfamily;
	Oid			opcintype;
	int16		strategy;

	/* Find the operator in pg_amop */
	if (get_ordering_op_properties(opno,
								   &opfamily, &opcintype, &strategy))
	{
		/* Found a suitable opfamily, get matching equality operator */
		result = get_opfamily_member(opfamily,
									 opcintype,
									 opcintype,
									 BTEqualStrategyNumber);
	}

	return result;
}

/*
 * get_ordering_op_for_equality_op
 *		Get the OID of a datatype-specific btree ordering operator
 *		associated with an equality operator.  (If there are multiple
 *		possibilities, assume any one will do.)
 *
 * This function is used when we have to sort data before unique-ifying,
 * and don't much care which sorting op is used as long as it's compatible
 * with the intended equality operator.  Since we need a sorting operator,
 * it should be single-data-type even if the given operator is cross-type.
 * The caller specifies whether to find an op for the LHS or RHS data type.
 *
 * Returns InvalidOid if no matching ordering operator can be found.
 */
Oid
get_ordering_op_for_equality_op(Oid opno, bool use_lhs_type)
{
	Oid			result = InvalidOid;
	CatCList   *catlist;
	int			i;

	/*
	 * Search pg_amop to see if the target operator is registered as the "="
	 * 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 == BTEqualStrategyNumber)
		{
			/* Found a suitable opfamily, get matching ordering operator */
			Oid			typid;

			typid = use_lhs_type ? aform->amoplefttype : aform->amoprighttype;
			result = get_opfamily_member(aform->amopfamily,
										 typid, typid,
										 BTLessStrategyNumber);
			if (OidIsValid(result))
				break;
			/* failure probably shouldn't happen, but keep looking if so */
		}
	}

	ReleaseSysCacheList(catlist);

	return result;
}

/*
 * get_mergejoin_opfamilies
 *		Given a putatively mergejoinable operator, return a list of the OIDs
 *		of the btree opfamilies in which it represents equality.
 *
 * It is possible (though at present unusual) for an operator to be equality
 * in more than one opfamily, hence the result is a list.  This also lets us
 * return NIL if the operator is not found in any opfamilies.
 *
 * The planner currently uses simple equal() tests to compare the lists
 * returned by this function, which makes the list order relevant, though
 * strictly speaking it should not be.	Because of the way syscache list
 * searches are handled, in normal operation the result will be sorted by OID
 * so everything works fine.  If running with system index usage disabled,
 * the result ordering is unspecified and hence the planner might fail to
 * recognize optimization opportunities ... but that's hardly a scenario in
 * which performance is good anyway, so there's no point in expending code
 * or cycles here to guarantee the ordering in that case.
 */
List *
get_mergejoin_opfamilies(Oid opno)
{
	List	   *result = NIL;
	CatCList   *catlist;
	int			i;

	/*
	 * Search pg_amop to see if the target operator is registered as the "="
	 * 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 equality */
		if (aform->amopmethod == BTREE_AM_OID &&
			aform->amopstrategy == BTEqualStrategyNumber)
			result = lappend_oid(result, aform->amopfamily);
	}

	ReleaseSysCacheList(catlist);

	return result;
}

/*
 * get_compatible_hash_operators
 *		Get the OID(s) of hash equality operator(s) compatible with the given
 *		operator, but operating on its LHS and/or RHS datatype.
 *
 * An operator for the LHS type is sought and returned into *lhs_opno if
 * lhs_opno isn't NULL.  Similarly, an operator for the RHS type is sought
 * and returned into *rhs_opno if rhs_opno isn't NULL.
 *
 * If the given operator is not cross-type, the results should be the same
 * operator, but in cross-type situations they will be different.
 *
 * Returns true if able to find the requested operator(s), false if not.
 * (This indicates that the operator should not have been marked oprcanhash.)
 */
bool
get_compatible_hash_operators(Oid opno,
							  Oid *lhs_opno, Oid *rhs_opno)
{
	bool		result = false;
	CatCList   *catlist;
	int			i;

	/* Ensure output args are initialized on failure */
	if (lhs_opno)
		*lhs_opno = InvalidOid;
	if (rhs_opno)
		*rhs_opno = InvalidOid;

	/*
	 * Search pg_amop to see if the target operator is registered as the "="
	 * operator of any hash opfamily.  If the operator is registered in
	 * multiple opfamilies, assume we can use 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->amopmethod == HASH_AM_OID &&
			aform->amopstrategy == HTEqualStrategyNumber)
		{
			/* No extra lookup needed if given operator is single-type */
			if (aform->amoplefttype == aform->amoprighttype)
			{
				if (lhs_opno)
					*lhs_opno = opno;
				if (rhs_opno)
					*rhs_opno = opno;
				result = true;
				break;
			}

			/*
			 * Get the matching single-type operator(s).  Failure probably
			 * shouldn't happen --- it implies a bogus opfamily --- but
			 * continue looking if so.
			 */
			if (lhs_opno)
			{
				*lhs_opno = get_opfamily_member(aform->amopfamily,
												aform->amoplefttype,
												aform->amoplefttype,
												HTEqualStrategyNumber);
				if (!OidIsValid(*lhs_opno))
					continue;
				/* Matching LHS found, done if caller doesn't want RHS */
				if (!rhs_opno)
				{
					result = true;
					break;
				}
			}
			if (rhs_opno)
			{
				*rhs_opno = get_opfamily_member(aform->amopfamily,
												aform->amoprighttype,
												aform->amoprighttype,
												HTEqualStrategyNumber);
				if (!OidIsValid(*rhs_opno))
				{
					/* Forget any LHS operator from this opfamily */
					if (lhs_opno)
						*lhs_opno = InvalidOid;
					continue;
				}
				/* Matching RHS found, so done */
				result = true;
				break;
			}
		}
	}

	ReleaseSysCacheList(catlist);

	return result;
}

/*
 * get_op_hash_functions
 *		Get the OID(s) of hash support function(s) compatible with the given
 *		operator, operating on its LHS and/or RHS datatype as required.
 *
 * A function for the LHS type is sought and returned into *lhs_procno if
 * lhs_procno isn't NULL.  Similarly, a function for the RHS type is sought
 * and returned into *rhs_procno if rhs_procno isn't NULL.
 *
 * If the given operator is not cross-type, the results should be the same
 * function, but in cross-type situations they will be different.
 *
 * Returns true if able to find the requested function(s), false if not.
 * (This indicates that the operator should not have been marked oprcanhash.)
 */
bool
get_op_hash_functions(Oid opno,
					  RegProcedure *lhs_procno, RegProcedure *rhs_procno)
{
	bool		result = false;
	CatCList   *catlist;
	int			i;

	/* Ensure output args are initialized on failure */
	if (lhs_procno)
		*lhs_procno = InvalidOid;
	if (rhs_procno)
		*rhs_procno = InvalidOid;

	/*
	 * Search pg_amop to see if the target operator is registered as the "="
	 * operator of any hash opfamily.  If the operator is registered in
	 * multiple opfamilies, assume we can use 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->amopmethod == HASH_AM_OID &&
			aform->amopstrategy == HTEqualStrategyNumber)
		{
			/*