/*-------------------------------------------------------------------------
 *
 * lsyscache.c
 *	  Convenience routines for common queries in the system catalog cache.
 *
 * Portions Copyright (c) 1996-2002, 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 1.80 2002/08/26 17:53:59 tgl Exp $
 *
 * NOTES
 *	  Eventually, the index information should go through here, too.
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/tupmacs.h"
#include "catalog/pg_amop.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/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(opclass),
								ObjectIdGetDatum(opno),
								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(opclass),
						ObjectIdGetDatum(opno),
						0, 0);
	if (!HeapTupleIsValid(tp))
		elog(ERROR, "op_requires_recheck: op %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;
}

/*				---------- 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 operator.
 */
char *
get_attname(Oid relid, AttrNumber attnum)
{
	HeapTuple	tp;

	tp = SearchSysCache(ATTNUM,
						ObjectIdGetDatum(relid),
						Int16GetDatum(attnum),
						0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_attribute att_tup = (Form_pg_attribute) GETSTRUCT(tp);
		char	   *result;

		result = pstrdup(NameStr(att_tup->attname));
		ReleaseSysCache(tp);
		return result;
	}
	else
		return NULL;
}

/*
 * get_attnum
 *
 *		Given the relation id and the attribute name,
 *		return the "attnum" field from the attribute relation.
 *
 *		Returns InvalidAttrNumber if the attr doesn't exist (or is dropped).
 */
AttrNumber
get_attnum(Oid relid, const char *attname)
{
	HeapTuple	tp;

	tp = SearchSysCacheAttName(relid, attname);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_attribute att_tup = (Form_pg_attribute) GETSTRUCT(tp);
		AttrNumber	result;

		result = att_tup->attnum;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return InvalidAttrNumber;
}

/*
 * get_atttype
 *
 *		Given the relation OID and the attribute number with the relation,
 *		return the attribute type OID.
 */
Oid
get_atttype(Oid relid, AttrNumber attnum)
{
	HeapTuple	tp;

	tp = SearchSysCache(ATTNUM,
						ObjectIdGetDatum(relid),
						Int16GetDatum(attnum),
						0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_attribute att_tup = (Form_pg_attribute) GETSTRUCT(tp);
		Oid			result;

		result = att_tup->atttypid;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return InvalidOid;
}

/*
 * get_atttypmod
 *
 *		Given the relation id and the attribute number,
 *		return the "atttypmod" field from the attribute relation.
 */
int32
get_atttypmod(Oid relid, AttrNumber attnum)
{
	HeapTuple	tp;

	tp = SearchSysCache(ATTNUM,
						ObjectIdGetDatum(relid),
						Int16GetDatum(attnum),
						0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_attribute att_tup = (Form_pg_attribute) GETSTRUCT(tp);
		int32		result;

		result = att_tup->atttypmod;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return -1;
}

/*
 * get_atttypetypmod
 *
 *		A two-fer: given the relation id and the attribute number,
 *		fetch both type OID and atttypmod in a single cache lookup.
 *
 * Unlike the otherwise-similar get_atttype/get_atttypmod, this routine
 * raises an error if it can't obtain the information.
 */
void
get_atttypetypmod(Oid relid, AttrNumber attnum,
				  Oid *typid, int32 *typmod)
{
	HeapTuple	tp;
	Form_pg_attribute att_tup;

	tp = SearchSysCache(ATTNUM,
						ObjectIdGetDatum(relid),
						Int16GetDatum(attnum),
						0, 0);
	if (!HeapTupleIsValid(tp))
		elog(ERROR, "cache lookup failed for relation %u attribute %d",
			 relid, attnum);
	att_tup = (Form_pg_attribute) GETSTRUCT(tp);

	*typid = att_tup->atttypid;
	*typmod = att_tup->atttypmod;
	ReleaseSysCache(tp);
}

/*				---------- INDEX CACHE ----------						 */

/*		watch this space...
 */

/*				---------- OPCLASS CACHE ----------						 */

/*
 * opclass_is_btree
 *
 *		Returns TRUE iff the specified opclass is associated with the
 *		btree index access method.
 */
bool
opclass_is_btree(Oid opclass)
{
	HeapTuple	tp;
	Form_pg_opclass cla_tup;
	bool		result;

	tp = SearchSysCache(CLAOID,
						ObjectIdGetDatum(opclass),
						0, 0, 0);
	if (!HeapTupleIsValid(tp))
		elog(ERROR, "cache lookup failed for opclass %u", opclass);
	cla_tup = (Form_pg_opclass) GETSTRUCT(tp);

	result = (cla_tup->opcamid == BTREE_AM_OID);
	ReleaseSysCache(tp);
	return result;
}

/*				---------- OPERATOR CACHE ----------					 */

/*
 * get_opcode
 *
 *		Returns the regproc id of the routine used to implement an
 *		operator given the operator oid.
 */
RegProcedure
get_opcode(Oid opno)
{
	HeapTuple	tp;

	tp = SearchSysCache(OPEROID,
						ObjectIdGetDatum(opno),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_operator optup = (Form_pg_operator) GETSTRUCT(tp);
		RegProcedure result;

		result = optup->oprcode;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return (RegProcedure) InvalidOid;
}

/*
 * get_opname
 *	  returns the name of the operator with the given opno
 *
 * Note: returns a palloc'd copy of the string, or NULL if no such operator.
 */
char *
get_opname(Oid opno)
{
	HeapTuple	tp;

	tp = SearchSysCache(OPEROID,
						ObjectIdGetDatum(opno),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_operator optup = (Form_pg_operator) GETSTRUCT(tp);
		char	   *result;

		result = pstrdup(NameStr(optup->oprname));
		ReleaseSysCache(tp);
		return result;
	}
	else
		return NULL;
}

/*
 * op_mergejoinable
 *
 *		Returns the left and right sort operators and types corresponding to a
 *		mergejoinable operator, or nil if the operator is not mergejoinable.
 */
bool
op_mergejoinable(Oid opno, Oid ltype, Oid rtype, Oid *leftOp, Oid *rightOp)
{
	HeapTuple	tp;
	bool		result = false;

	tp = SearchSysCache(OPEROID,
						ObjectIdGetDatum(opno),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_operator optup = (Form_pg_operator) GETSTRUCT(tp);

		if (optup->oprlsortop &&
			optup->oprrsortop &&
			optup->oprleft == ltype &&
			optup->oprright == rtype)
		{
			*leftOp = optup->oprlsortop;
			*rightOp = optup->oprrsortop;
			result = true;
		}
		ReleaseSysCache(tp);
	}
	return result;
}

/*
 * op_mergejoin_crossops
 *
 *		Returns the cross-type comparison operators (ltype "<" rtype and
 *		ltype ">" rtype) for an operator previously determined to be
 *		mergejoinable.  Optionally, fetches the regproc ids of these
 *		operators, as well as their operator OIDs.
 */
void
op_mergejoin_crossops(Oid opno, Oid *ltop, Oid *gtop,
					  RegProcedure *ltproc, RegProcedure *gtproc)
{
	HeapTuple	tp;
	Form_pg_operator optup;

	/*
	 * Get the declared comparison operators of the operator.
	 */
	tp = SearchSysCache(OPEROID,
						ObjectIdGetDatum(opno),
						0, 0, 0);
	if (!HeapTupleIsValid(tp))	/* shouldn't happen */
		elog(ERROR, "op_mergejoin_crossops: operator %u not found", opno);
	optup = (Form_pg_operator) GETSTRUCT(tp);
	*ltop = optup->oprltcmpop;
	*gtop = optup->oprgtcmpop;
	ReleaseSysCache(tp);

	/* Check < op provided */
	if (!OidIsValid(*ltop))
		elog(ERROR, "op_mergejoin_crossops: mergejoin operator %u has no matching < operator",
			 opno);
	if (ltproc)
		*ltproc = get_opcode(*ltop);

	/* Check > op provided */
	if (!OidIsValid(*gtop))
		elog(ERROR, "op_mergejoin_crossops: mergejoin operator %u has no matching > operator",
			 opno);
	if (gtproc)
		*gtproc = get_opcode(*gtop);
}

/*
 * op_hashjoinable
 *
 * Returns the hash operator corresponding to a hashjoinable operator,
 * or InvalidOid if the operator is not hashjoinable.
 */
Oid
op_hashjoinable(Oid opno, Oid ltype, Oid rtype)
{
	HeapTuple	tp;
	Oid			result = InvalidOid;

	tp = SearchSysCache(OPEROID,
						ObjectIdGetDatum(opno),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_operator optup = (Form_pg_operator) GETSTRUCT(tp);

		if (optup->oprcanhash &&
			optup->oprleft == ltype &&
			optup->oprright == rtype)
			result = opno;
		ReleaseSysCache(tp);
	}
	return result;
}

/*
 * op_volatile
 *
 * Get the provolatile flag for the operator's underlying function.
 */
char
op_volatile(Oid opno)
{
	RegProcedure funcid = get_opcode(opno);

	if (funcid == (RegProcedure) InvalidOid)
		elog(ERROR, "Operator OID %u does not exist", opno);

	return func_volatile((Oid) funcid);
}

/*
 * get_commutator
 *
 *		Returns the corresponding commutator of an operator.
 */
Oid
get_commutator(Oid opno)
{
	HeapTuple	tp;

	tp = SearchSysCache(OPEROID,
						ObjectIdGetDatum(opno),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_operator optup = (Form_pg_operator) GETSTRUCT(tp);
		Oid			result;

		result = optup->oprcom;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return InvalidOid;
}

/*
 * get_negator
 *
 *		Returns the corresponding negator of an operator.
 */
Oid
get_negator(Oid opno)
{
	HeapTuple	tp;

	tp = SearchSysCache(OPEROID,
						ObjectIdGetDatum(opno),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_operator optup = (Form_pg_operator) GETSTRUCT(tp);
		Oid			result;

		result = optup->oprnegate;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return InvalidOid;
}

/*
 * get_oprrest
 *
 *		Returns procedure id for computing selectivity of an operator.
 */
RegProcedure
get_oprrest(Oid opno)
{
	HeapTuple	tp;

	tp = SearchSysCache(OPEROID,
						ObjectIdGetDatum(opno),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_operator optup = (Form_pg_operator) GETSTRUCT(tp);
		RegProcedure result;

		result = optup->oprrest;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return (RegProcedure) InvalidOid;
}

/*
 * get_oprjoin
 *
 *		Returns procedure id for computing selectivity of a join.
 */
RegProcedure
get_oprjoin(Oid opno)
{
	HeapTuple	tp;

	tp = SearchSysCache(OPEROID,
						ObjectIdGetDatum(opno),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_operator optup = (Form_pg_operator) GETSTRUCT(tp);
		RegProcedure result;

		result = optup->oprjoin;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return (RegProcedure) InvalidOid;
}

/*				---------- FUNCTION CACHE ----------					 */

/*
 * get_func_name
 *	  returns the name of the function with the given funcid
 *
 * Note: returns a palloc'd copy of the string, or NULL if no such function.
 */
char *
get_func_name(Oid funcid)
{
	HeapTuple	tp;

	tp = SearchSysCache(PROCOID,
						ObjectIdGetDatum(funcid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_proc functup = (Form_pg_proc) GETSTRUCT(tp);
		char	   *result;

		result = pstrdup(NameStr(functup->proname));
		ReleaseSysCache(tp);
		return result;
	}
	else
		return NULL;
}

/*
 * get_func_rettype
 *		Given procedure id, return the function's result type.
 */
Oid
get_func_rettype(Oid funcid)
{
	HeapTuple	tp;
	Oid			result;

	tp = SearchSysCache(PROCOID,
						ObjectIdGetDatum(funcid),
						0, 0, 0);
	if (!HeapTupleIsValid(tp))
		elog(ERROR, "Function OID %u does not exist", funcid);

	result = ((Form_pg_proc) GETSTRUCT(tp))->prorettype;
	ReleaseSysCache(tp);
	return result;
}

/*
 * get_func_retset
 *		Given procedure id, return the function's proretset flag.
 */
bool
get_func_retset(Oid funcid)
{
	HeapTuple	tp;
	bool		result;

	tp = SearchSysCache(PROCOID,
						ObjectIdGetDatum(funcid),
						0, 0, 0);
	if (!HeapTupleIsValid(tp))
		elog(ERROR, "Function OID %u does not exist", funcid);

	result = ((Form_pg_proc) GETSTRUCT(tp))->proretset;
	ReleaseSysCache(tp);
	return result;
}

/*
 * func_volatile
 *		Given procedure id, return the function's provolatile flag.
 */
char
func_volatile(Oid funcid)
{
	HeapTuple	tp;
	char		result;

	tp = SearchSysCache(PROCOID,
						ObjectIdGetDatum(funcid),
						0, 0, 0);
	if (!HeapTupleIsValid(tp))
		elog(ERROR, "Function OID %u does not exist", funcid);

	result = ((Form_pg_proc) GETSTRUCT(tp))->provolatile;
	ReleaseSysCache(tp);
	return result;
}

/*				---------- RELATION CACHE ----------					 */

/*
 * get_relname_relid
 *		Given name and namespace of a relation, look up the OID.
 *
 * Returns InvalidOid if there is no such relation.
 */
Oid
get_relname_relid(const char *relname, Oid relnamespace)
{
	return GetSysCacheOid(RELNAMENSP,
						  PointerGetDatum(relname),
						  ObjectIdGetDatum(relnamespace),
						  0, 0);
}

/*
 * get_system_catalog_relid
 *		Get the OID of a system catalog identified by name.
 */
Oid
get_system_catalog_relid(const char *catname)
{
	Oid		relid;

	relid = GetSysCacheOid(RELNAMENSP,
						   PointerGetDatum(catname),
						   ObjectIdGetDatum(PG_CATALOG_NAMESPACE),
						   0, 0);
	if (!OidIsValid(relid))
		elog(ERROR, "get_system_catalog_relid: cannot find %s", catname);

	return relid;
}

#ifdef NOT_USED
/*
 * get_relnatts
 *
 *		Returns the number of attributes for a given relation.
 */
int
get_relnatts(Oid relid)
{
	HeapTuple	tp;

	tp = SearchSysCache(RELOID,
						ObjectIdGetDatum(relid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_class reltup = (Form_pg_class) GETSTRUCT(tp);
		int			result;

		result = reltup->relnatts;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return InvalidAttrNumber;
}
#endif

/*
 * get_rel_name
 *		Returns the name of a given relation.
 *
 * Returns a palloc'd copy of the string, or NULL if no such relation.
 *
 * NOTE: since relation name is not unique, be wary of code that uses this
 * for anything except preparing error messages.
 */
char *
get_rel_name(Oid relid)
{
	HeapTuple	tp;

	tp = SearchSysCache(RELOID,
						ObjectIdGetDatum(relid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_class reltup = (Form_pg_class) GETSTRUCT(tp);
		char	   *result;

		result = pstrdup(NameStr(reltup->relname));
		ReleaseSysCache(tp);
		return result;
	}
	else
		return NULL;
}

/*
 * get_rel_namespace
 *
 *		Returns the pg_namespace OID associated with a given relation.
 */
Oid
get_rel_namespace(Oid relid)
{
	HeapTuple	tp;

	tp = SearchSysCache(RELOID,
						ObjectIdGetDatum(relid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_class reltup = (Form_pg_class) GETSTRUCT(tp);
		Oid		result;

		result = reltup->relnamespace;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return InvalidOid;
}

/*
 * get_rel_type_id
 *
 *		Returns the pg_type OID associated with a given relation.
 *
 * Note: not all pg_class entries have associated pg_type OIDs; so be
 * careful to check for InvalidOid result.
 */
Oid
get_rel_type_id(Oid relid)
{
	HeapTuple	tp;

	tp = SearchSysCache(RELOID,
						ObjectIdGetDatum(relid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_class reltup = (Form_pg_class) GETSTRUCT(tp);
		Oid		result;

		result = reltup->reltype;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return InvalidOid;
}

/*				---------- TYPE CACHE ----------						 */

/*
 * get_typisdefined
 *
 *		Given the type OID, determine whether the type is defined
 *		(if not, it's only a shell).
 */
bool
get_typisdefined(Oid typid)
{
	HeapTuple	tp;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
		bool		result;

		result = typtup->typisdefined;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return false;
}

/*
 * get_typlen
 *
 *		Given the type OID, return the length of the type.
 */
int16
get_typlen(Oid typid)
{
	HeapTuple	tp;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
		int16		result;

		result = typtup->typlen;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return 0;
}

/*
 * get_typbyval
 *
 *		Given the type OID, determine whether the type is returned by value or
 *		not.  Returns true if by value, false if by reference.
 */
bool
get_typbyval(Oid typid)
{
	HeapTuple	tp;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
		bool		result;

		result = typtup->typbyval;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return false;
}

/*
 * get_typlenbyval
 *
 *		A two-fer: given the type OID, return both typlen and typbyval.
 *
 *		Since both pieces of info are needed to know how to copy a Datum,
 *		many places need both.	Might as well get them with one cache lookup
 *		instead of two.  Also, this routine raises an error instead of
 *		returning a bogus value when given a bad type OID.
 */
void
get_typlenbyval(Oid typid, int16 *typlen, bool *typbyval)
{
	HeapTuple	tp;
	Form_pg_type typtup;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (!HeapTupleIsValid(tp))
		elog(ERROR, "cache lookup failed for type %u", typid);
	typtup = (Form_pg_type) GETSTRUCT(tp);
	*typlen = typtup->typlen;
	*typbyval = typtup->typbyval;
	ReleaseSysCache(tp);
}

/*
 * get_typlenbyvalalign
 *
 *		A three-fer: given the type OID, return typlen, typbyval, typalign.
 */
void
get_typlenbyvalalign(Oid typid, int16 *typlen, bool *typbyval,
					 char *typalign)
{
	HeapTuple	tp;
	Form_pg_type typtup;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (!HeapTupleIsValid(tp))
		elog(ERROR, "cache lookup failed for type %u", typid);
	typtup = (Form_pg_type) GETSTRUCT(tp);
	*typlen = typtup->typlen;
	*typbyval = typtup->typbyval;
	*typalign = typtup->typalign;
	ReleaseSysCache(tp);
}

#ifdef NOT_USED
char
get_typalign(Oid typid)
{
	HeapTuple	tp;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
		char		result;

		result = typtup->typalign;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return 'i';
}
#endif

char
get_typstorage(Oid typid)
{
	HeapTuple	tp;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
		char		result;

		result = typtup->typstorage;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return 'p';
}

/*
 * get_typdefault
 *	  Given a type OID, return the type's default value, if any.
 *
 *	  The result is a palloc'd expression node tree, or NULL if there
 *	  is no defined default for the datatype.
 *
 * NB: caller should be prepared to coerce result to correct datatype;
 * the returned expression tree might produce something of the wrong type.
 */
Node *
get_typdefault(Oid typid)
{
	HeapTuple	typeTuple;
	Form_pg_type type;
	Datum		datum;
	bool		isNull;
	Node	   *expr;

	typeTuple = SearchSysCache(TYPEOID,
							   ObjectIdGetDatum(typid),
							   0, 0, 0);
	if (!HeapTupleIsValid(typeTuple))
		elog(ERROR, "get_typdefault: failed to lookup type %u", typid);
	type = (Form_pg_type) GETSTRUCT(typeTuple);

	/*
	 * typdefault and typdefaultbin are potentially null, so don't try to
	 * access 'em as struct fields. Must do it the hard way with
	 * SysCacheGetAttr.
	 */
	datum = SysCacheGetAttr(TYPEOID,
							typeTuple,
							Anum_pg_type_typdefaultbin,
							&isNull);

	if (!isNull)
	{
		/* We have an expression default */
		expr = stringToNode(DatumGetCString(DirectFunctionCall1(textout,
																datum)));
	}
	else
	{
		/* Perhaps we have a plain literal default */
		datum = SysCacheGetAttr(TYPEOID,
								typeTuple,
								Anum_pg_type_typdefault,
								&isNull);

		if (!isNull)
		{
			char	   *strDefaultVal;

			/* Convert text datum to C string */
			strDefaultVal = DatumGetCString(DirectFunctionCall1(textout,
																datum));
			/* Convert C string to a value of the given type */
			datum = OidFunctionCall3(type->typinput,
									 CStringGetDatum(strDefaultVal),
									 ObjectIdGetDatum(type->typelem),
									 Int32GetDatum(-1));
			/* Build a Const node containing the value */
			expr = (Node *) makeConst(typid,
									  type->typlen,
									  datum,
									  false,
									  type->typbyval,
									  false,	/* not a set */
									  false);
			pfree(strDefaultVal);
		}
		else
		{
			/* No default */
			expr = NULL;
		}
	}

	ReleaseSysCache(typeTuple);

	return expr;
}

/*
 * getBaseType
 *		If the given type is a domain, return its base type;
 *		otherwise return the type's own OID.
 */
Oid
getBaseType(Oid typid)
{
	/*
	 * We loop to find the bottom base type in a stack of domains.
	 */
	for (;;)
	{
		HeapTuple	tup;
		Form_pg_type typTup;

		tup = SearchSysCache(TYPEOID,
							 ObjectIdGetDatum(typid),
							 0, 0, 0);
		if (!HeapTupleIsValid(tup))
			elog(ERROR, "getBaseType: failed to lookup type %u", typid);
		typTup = (Form_pg_type) GETSTRUCT(tup);
		if (typTup->typtype != 'd')
		{
			/* Not a domain, so done */
			ReleaseSysCache(tup);
			break;
		}

		typid = typTup->typbasetype;
		ReleaseSysCache(tup);
	}

	return typid;
}

/*
 * getBaseTypeTypeMod
 *		If the given type is a domain, return its base type;
 *		otherwise return the type's own OID.  Also return base typmod.
 */
Oid
getBaseTypeTypeMod(Oid typid, int32 *typmod)
{
	/*
	 * We loop to find the bottom base type in a stack of domains.
	 */
	for (;;)
	{
		HeapTuple	tup;
		Form_pg_type typTup;

		tup = SearchSysCache(TYPEOID,
							 ObjectIdGetDatum(typid),
							 0, 0, 0);
		if (!HeapTupleIsValid(tup))
			elog(ERROR, "getBaseTypeTypeMod: failed to lookup type %u", typid);
		typTup = (Form_pg_type) GETSTRUCT(tup);
		if (typTup->typtype != 'd')
		{
			/* Not a domain, so done */
			ReleaseSysCache(tup);
			break;
		}

		typid = typTup->typbasetype;
		*typmod = typTup->typtypmod;
		ReleaseSysCache(tup);
	}

	return typid;
}

/*
 * get_typavgwidth
 *
 *	  Given a type OID and a typmod value (pass -1 if typmod is unknown),
 *	  estimate the average width of values of the type.  This is used by
 *	  the planner, which doesn't require absolutely correct results;
 *	  it's OK (and expected) to guess if we don't know for sure.
 */
int32
get_typavgwidth(Oid typid, int32 typmod)
{
	int			typlen = get_typlen(typid);
	int32		maxwidth;

	/*
	 * Easy if it's a fixed-width type
	 */
	if (typlen > 0)
		return typlen;

	/*
	 * type_maximum_size knows the encoding of typmod for some datatypes;
	 * don't duplicate that knowledge here.
	 */
	maxwidth = type_maximum_size(typid, typmod);
	if (maxwidth > 0)
	{
		/*
		 * For BPCHAR, the max width is also the only width.  Otherwise we
		 * need to guess about the typical data width given the max. A
		 * sliding scale for percentage of max width seems reasonable.
		 */
		if (typid == BPCHAROID)
			return maxwidth;
		if (maxwidth <= 32)
			return maxwidth;	/* assume full width */
		if (maxwidth < 1000)
			return 32 + (maxwidth - 32) / 2;	/* assume 50% */

		/*
		 * Beyond 1000, assume we're looking at something like
		 * "varchar(10000)" where the limit isn't actually reached often,
		 * and use a fixed estimate.
		 */
		return 32 + (1000 - 32) / 2;
	}

	/*
	 * Ooops, we have no idea ... wild guess time.
	 */
	return 32;
}

/*
 * get_typtype
 *
 *		Given the type OID, find if it is a basic type, a complex type, etc.
 *		It returns the null char if the cache lookup fails...
 */
char
get_typtype(Oid typid)
{
	HeapTuple	tp;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
		char		result;

		result = typtup->typtype;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return '\0';
}

/*
 * getTypeOutputInfo
 *
 *		Get info needed for printing values of a type
 *
 * Returns true if data valid (a false result probably means it's a shell type)
 */
bool
getTypeOutputInfo(Oid type, Oid *typOutput, Oid *typElem,
				  bool *typIsVarlena)
{
	HeapTuple	typeTuple;
	Form_pg_type pt;

	typeTuple = SearchSysCache(TYPEOID,
							   ObjectIdGetDatum(type),
							   0, 0, 0);
	if (!HeapTupleIsValid(typeTuple))
		elog(ERROR, "getTypeOutputInfo: Cache lookup of type %u failed", type);
	pt = (Form_pg_type) GETSTRUCT(typeTuple);

	*typOutput = pt->typoutput;
	*typElem = pt->typelem;
	*typIsVarlena = (!pt->typbyval) && (pt->typlen == -1);
	ReleaseSysCache(typeTuple);
	return OidIsValid(*typOutput);
}


/*				---------- STATISTICS CACHE ----------					 */

/*
 * get_attavgwidth
 *
 *	  Given the table and attribute number of a column, get the average
 *	  width of entries in the column.  Return zero if no data available.
 */
int32
get_attavgwidth(Oid relid, AttrNumber attnum)
{
	HeapTuple	tp;

	tp = SearchSysCache(STATRELATT,
						ObjectIdGetDatum(relid),
						Int16GetDatum(attnum),
						0, 0);
	if (HeapTupleIsValid(tp))
	{
		int32		stawidth = ((Form_pg_statistic) GETSTRUCT(tp))->stawidth;

		ReleaseSysCache(tp);
		if (stawidth > 0)
			return stawidth;
	}
	return 0;
}

/*
 * get_attstatsslot
 *
 *		Extract the contents of a "slot" of a pg_statistic tuple.
 *		Returns TRUE if requested slot type was found, else FALSE.
 *
 * Unlike other routines in this file, this takes a pointer to an
 * already-looked-up tuple in the pg_statistic cache.  We do this since
 * most callers will want to extract more than one value from the cache
 * entry, and we don't want to repeat the cache lookup unnecessarily.
 *
 * statstuple: pg_statistics tuple to be examined.
 * atttype: type OID of attribute.
 * atttypmod: typmod of attribute.
 * reqkind: STAKIND code for desired statistics slot kind.
 * reqop: STAOP value wanted, or InvalidOid if don't care.
 * values, nvalues: if not NULL, the slot's stavalues are extracted.
 * numbers, nnumbers: if not NULL, the slot's stanumbers are extracted.
 *
 * If assigned, values and numbers are set to point to palloc'd arrays.
 * If the attribute type is pass-by-reference, the values referenced by
 * the values array are themselves palloc'd.  The palloc'd stuff can be
 * freed by calling free_attstatsslot.
 */
bool
get_attstatsslot(HeapTuple statstuple,
				 Oid atttype, int32 atttypmod,
				 int reqkind, Oid reqop,
				 Datum **values, int *nvalues,
				 float4 **numbers, int *nnumbers)
{
	Form_pg_statistic stats = (Form_pg_statistic) GETSTRUCT(statstuple);
	int			i,
				j;
	Datum		val;
	bool		isnull;
	ArrayType  *statarray;
	int			narrayelem;
	HeapTuple	typeTuple;
	FmgrInfo	inputproc;
	Oid			typelem;

	for (i = 0; i < STATISTIC_NUM_SLOTS; i++)
	{
		if ((&stats->stakind1)[i] == reqkind &&
			(reqop == InvalidOid || (&stats->staop1)[i] == reqop))
			break;
	}
	if (i >= STATISTIC_NUM_SLOTS)
		return false;			/* not there */

	if (values)
	{
		val = SysCacheGetAttr(STATRELATT, statstuple,
							  Anum_pg_statistic_stavalues1 + i,
							  &isnull);
		if (isnull)
			elog(ERROR, "get_attstatsslot: stavalues is null");
		statarray = DatumGetArrayTypeP(val);

		/*
		 * Do initial examination of the array.  This produces a list of
		 * text Datums --- ie, pointers into the text array value.
		 */
		deconstruct_array(statarray,
						  TEXTOID, -1, false, 'i',
						  values, nvalues);
		narrayelem = *nvalues;

		/*
		 * We now need to replace each text Datum by its internal
		 * equivalent.
		 *
		 * Get the type input proc and typelem for the column datatype.
		 */
		typeTuple = SearchSysCache(TYPEOID,
								   ObjectIdGetDatum(atttype),
								   0, 0, 0);
		if (!HeapTupleIsValid(typeTuple))
			elog(ERROR, "get_attstatsslot: Cache lookup failed for type %u",
				 atttype);
		fmgr_info(((Form_pg_type) GETSTRUCT(typeTuple))->typinput, &inputproc);
		typelem = ((Form_pg_type) GETSTRUCT(typeTuple))->typelem;
		ReleaseSysCache(typeTuple);

		/*
		 * Do the conversions.	The palloc'd array of Datums is reused in
		 * place.
		 */
		for (j = 0; j < narrayelem; j++)
		{
			char	   *strval;

			strval = DatumGetCString(DirectFunctionCall1(textout,
														 (*values)[j]));
			(*values)[j] = FunctionCall3(&inputproc,
										 CStringGetDatum(strval),
										 ObjectIdGetDatum(typelem),
										 Int32GetDatum(atttypmod));
			pfree(strval);
		}

		/*
		 * Free statarray if it's a detoasted copy.
		 */
		if ((Pointer) statarray != DatumGetPointer(val))
			pfree(statarray);
	}

	if (numbers)
	{
		val = SysCacheGetAttr(STATRELATT, statstuple,
							  Anum_pg_statistic_stanumbers1 + i,
							  &isnull);
		if (isnull)
			elog(ERROR, "get_attstatsslot: stanumbers is null");
		statarray = DatumGetArrayTypeP(val);

		/*
		 * We expect the array to be a 1-D float4 array; verify that. We
		 * don't need to use deconstruct_array() since the array data is
		 * just going to look like a C array of float4 values.
		 */
		narrayelem = ARR_DIMS(statarray)[0];
		if (ARR_NDIM(statarray) != 1 || narrayelem <= 0 ||
			ARR_ELEMTYPE(statarray) != FLOAT4OID)
			elog(ERROR, "get_attstatsslot: stanumbers is not a 1-D float4 array");
		*numbers = (float4 *) palloc(narrayelem * sizeof(float4));
		memcpy(*numbers, ARR_DATA_PTR(statarray), narrayelem * sizeof(float4));
		*nnumbers = narrayelem;

		/*
		 * Free statarray if it's a detoasted copy.
		 */
		if ((Pointer) statarray != DatumGetPointer(val))
			pfree(statarray);
	}

	return true;
}

void
free_attstatsslot(Oid atttype,
				  Datum *values, int nvalues,
				  float4 *numbers, int nnumbers)
{
	if (values)
	{
		if (!get_typbyval(atttype))
		{
			int			i;

			for (i = 0; i < nvalues; i++)
				pfree(DatumGetPointer(values[i]));
		}
		pfree(values);
	}
	if (numbers)
		pfree(numbers);
}

/*				---------- PG_NAMESPACE CACHE ----------				 */

/*
 * get_namespace_name
 *		Returns the name of a given namespace
 *
 * Returns a palloc'd copy of the string, or NULL if no such namespace.
 */
char *
get_namespace_name(Oid nspid)
{
	HeapTuple	tp;

	tp = SearchSysCache(NAMESPACEOID,
						ObjectIdGetDatum(nspid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_namespace nsptup = (Form_pg_namespace) GETSTRUCT(tp);
		char	   *result;

		result = pstrdup(NameStr(nsptup->nspname));
		ReleaseSysCache(tp);
		return result;
	}
	else
		return NULL;
}

/*				---------- PG_SHADOW CACHE ----------					 */

/*
 * get_usesysid
 *
 *	  Given a user name, look up the user's sysid.
 *	  Raises an error if no such user (rather than returning zero,
 *	  which might possibly be a valid usesysid).
 *
 * Note: the type of usesysid is currently int4, but may change to Oid
 * someday.  It'd be reasonable to return zero on failure if we were
 * using Oid ...
 */
int32
get_usesysid(const char *username)
{
	int32		result;
	HeapTuple	userTup;

	userTup = SearchSysCache(SHADOWNAME,
							 PointerGetDatum(username),
							 0, 0, 0);
	if (!HeapTupleIsValid(userTup))
		elog(ERROR, "user \"%s\" does not exist", username);

	result = ((Form_pg_shadow) GETSTRUCT(userTup))->usesysid;

	ReleaseSysCache(userTup);

	return result;
}
