lsyscache.c

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/*-------------------------------------------------------------------------
 *
 * lsyscache.c
 *    Convenience routines for common queries in the system catalog cache.
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/utils/cache/lsyscache.c
 *
 * NOTES
 *    Eventually, the index information should go through here, too.
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/hash.h"
#include "access/htup_details.h"
#include "access/nbtree.h"
#include "bootstrap/bootstrap.h"
#include "catalog/pg_amop.h"
#include "catalog/pg_amproc.h"
#include "catalog/pg_collation.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_range.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/catcache.h"
#include "utils/datum.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/syscache.h"
#include "utils/typcache.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'.
 *
 * This function only considers search operators, not ordering operators.
 */
bool
op_in_opfamily(Oid opno, Oid opfamily)
{
    return SearchSysCacheExists3(AMOPOPID,
                                 ObjectIdGetDatum(opno),
                                 CharGetDatum(AMOP_SEARCH),
                                 ObjectIdGetDatum(opfamily));
}

/*
 * 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.
 *
 * This function only considers search operators, not ordering operators.
 */
int
get_op_opfamily_strategy(Oid opno, Oid opfamily)
{
    HeapTuple   tp;
    Form_pg_amop amop_tup;
    int         result;

    tp = SearchSysCache3(AMOPOPID,
                         ObjectIdGetDatum(opno),
                         CharGetDatum(AMOP_SEARCH),
                         ObjectIdGetDatum(opfamily));
    if (!HeapTupleIsValid(tp))
        return 0;
    amop_tup = (Form_pg_amop) GETSTRUCT(tp);
    result = amop_tup->amopstrategy;
    ReleaseSysCache(tp);
    return result;
}

/*
 * get_op_opfamily_sortfamily
 *
 *      If the operator is an ordering operator within the specified opfamily,
 *      return its amopsortfamily OID; else return InvalidOid.
 */
Oid
get_op_opfamily_sortfamily(Oid opno, Oid opfamily)
{
    HeapTuple   tp;
    Form_pg_amop amop_tup;
    Oid         result;

    tp = SearchSysCache3(AMOPOPID,
                         ObjectIdGetDatum(opno),
                         CharGetDatum(AMOP_ORDER),
                         ObjectIdGetDatum(opfamily));
    if (!HeapTupleIsValid(tp))
        return InvalidOid;
    amop_tup = (Form_pg_amop) GETSTRUCT(tp);
    result = amop_tup->amopsortfamily;
    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, bool ordering_op,
                           int *strategy,
                           Oid *lefttype,
                           Oid *righttype)
{
    HeapTuple   tp;
    Form_pg_amop amop_tup;

    tp = SearchSysCache3(AMOPOPID,
                         ObjectIdGetDatum(opno),
                         CharGetDatum(ordering_op ? AMOP_ORDER : AMOP_SEARCH),
                         ObjectIdGetDatum(opfamily));
    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 = SearchSysCache4(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 = SearchSysCacheList1(AMOPOPID, ObjectIdGetDatum(opno));

    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_sort_function_for_ordering_op
 *      Get the OID of the datatype-specific btree sort support function,
 *      or if there is none, the btree comparison function,
 *      associated with an ordering operator (a "<" or ">" operator).
 *
 * *sortfunc receives the support or comparison function OID.
 * *issupport is set TRUE if it's a support func, FALSE if a comparison func.
 * *reverse is set FALSE if the operator is "<", TRUE if it's ">"
 * (indicating that comparison results 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_sort_function_for_ordering_op(Oid opno, Oid *sortfunc,
                                  bool *issupport, 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 */
        *sortfunc = get_opfamily_proc(opfamily,
                                      opcintype,
                                      opcintype,
                                      BTSORTSUPPORT_PROC);
        if (OidIsValid(*sortfunc))
            *issupport = true;
        else
        {
            /* opfamily doesn't provide sort support, get comparison func */
            *sortfunc = get_opfamily_proc(opfamily,
                                          opcintype,
                                          opcintype,
                                          BTORDER_PROC);
            if (!OidIsValid(*sortfunc)) /* should not happen */
                elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
                     BTORDER_PROC, opcintype, opcintype, opfamily);
            *issupport = false;
        }
        *reverse = (strategy == BTGreaterStrategyNumber);
        return true;
    }

    /* ensure outputs are set on failure */
    *sortfunc = InvalidOid;
    *issupport = false;
    *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).
 *
 * If "reverse" isn't NULL, also set *reverse to FALSE if the operator is "<",
 * TRUE if it's ">"
 *
 * 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, bool *reverse)
{
    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);
        if (reverse)
            *reverse = (strategy == BTGreaterStrategyNumber);
    }

    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 = SearchSysCacheList1(AMOPOPID, ObjectIdGetDatum(opno));

    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 = SearchSysCacheList1(AMOPOPID, ObjectIdGetDatum(opno));

    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 = SearchSysCacheList1(AMOPOPID, ObjectIdGetDatum(opno));

    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 = SearchSysCacheList1(AMOPOPID, ObjectIdGetDatum(opno));

    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)
        {
            /*
             * Get the matching support function(s).  Failure probably
             * shouldn't happen --- it implies a bogus opfamily --- but
             * continue looking if so.
             */
            if (lhs_procno)
            {
                *lhs_procno = get_opfamily_proc(aform->amopfamily,
                                                aform->amoplefttype,
                                                aform->amoplefttype,
                                                HASHPROC);
                if (!OidIsValid(*lhs_procno))
                    continue;
                /* Matching LHS found, done if caller doesn't want RHS */
                if (!rhs_procno)
                {
                    result = true;
                    break;
                }
                /* Only one lookup needed if given operator is single-type */
                if (aform->amoplefttype == aform->amoprighttype)
                {
                    *rhs_procno = *lhs_procno;
                    result = true;
                    break;
                }
            }
            if (rhs_procno)
            {
                *rhs_procno = get_opfamily_proc(aform->amopfamily,
                                                aform->amoprighttype,
                                                aform->amoprighttype,
                                                HASHPROC);
                if (!OidIsValid(*rhs_procno))
                {
                    /* Forget any LHS function from this opfamily */
                    if (lhs_procno)
                        *lhs_procno = InvalidOid;
                    continue;
                }
                /* Matching RHS found, so done */
                result = true;
                break;
            }
        }
    }

    ReleaseSysCacheList(catlist);

    return result;
}

/*
 * get_op_btree_interpretation
 *      Given an operator's OID, find out which btree opfamilies it belongs to,
 *      and what properties it has within each one.  The results are returned
 *      as a palloc'd list of OpBtreeInterpretation structs.
 *
 * In addition to the normal btree operators, we consider a <> operator to be
 * a "member" of an opfamily if its negator is an equality operator of the
 * opfamily.  ROWCOMPARE_NE is returned as the strategy number for this case.
 */
List *
get_op_btree_interpretation(Oid opno)
{
    List       *result = NIL;
    OpBtreeInterpretation *thisresult;
    CatCList   *catlist;
    int         i;

    /*
     * Find all the pg_amop entries containing the operator.
     */
    catlist = SearchSysCacheList1(AMOPOPID, ObjectIdGetDatum(opno));

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

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

        /* Get the operator's btree strategy number */
        op_strategy = (StrategyNumber) op_form->amopstrategy;
        Assert(op_strategy >= 1 && op_strategy <= 5);

        thisresult = (OpBtreeInterpretation *)
            palloc(sizeof(OpBtreeInterpretation));
        thisresult->opfamily_id = op_form->amopfamily;
        thisresult->strategy = op_strategy;
        thisresult->oplefttype = op_form->amoplefttype;
        thisresult->oprighttype = op_form->amoprighttype;
        result = lappend(result, thisresult);
    }

    ReleaseSysCacheList(catlist);

    /*
     * If we didn't find any btree opfamily containing the operator, perhaps
     * it is a <> operator.  See if it has a negator that is in an opfamily.
     */
    if (result == NIL)
    {
        Oid         op_negator = get_negator(opno);

        if (OidIsValid(op_negator))
        {
            catlist = SearchSysCacheList1(AMOPOPID,
                                          ObjectIdGetDatum(op_negator));

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

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

                /* Get the operator's btree strategy number */
                op_strategy = (StrategyNumber) op_form->amopstrategy;
                Assert(op_strategy >= 1 && op_strategy <= 5);

                /* Only consider negators that are = */
                if (op_strategy != BTEqualStrategyNumber)
                    continue;

                /* OK, report it with "strategy" ROWCOMPARE_NE */
                thisresult = (OpBtreeInterpretation *)
                    palloc(sizeof(OpBtreeInterpretation));
                thisresult->opfamily_id = op_form->amopfamily;
                thisresult->strategy = ROWCOMPARE_NE;
                thisresult->oplefttype = op_form->amoplefttype;
                thisresult->oprighttype = op_form->amoprighttype;
                result = lappend(result, thisresult);
            }

            ReleaseSysCacheList(catlist);
        }
    }

    return result;
}

/*
 * equality_ops_are_compatible
 *      Return TRUE if the two given equality operators have compatible
 *      semantics.
 *
 * This is trivially true if they are the same operator.  Otherwise,
 * we look to see if they can be found in the same btree or hash opfamily.
 * Either finding allows us to assume that they have compatible notions
 * of equality.  (The reason we need to do these pushups is that one might
 * be a cross-type operator; for instance int24eq vs int4eq.)
 */
bool
equality_ops_are_compatible(Oid opno1, Oid opno2)
{
    bool        result;
    CatCList   *catlist;
    int         i;

    /* Easy if they're the same operator */
    if (opno1 == opno2)
        return true;

    /*
     * We search through all the pg_amop entries for opno1.
     */
    catlist = SearchSysCacheList1(AMOPOPID, ObjectIdGetDatum(opno1));

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

        /* must be btree or hash */
        if (op_form->amopmethod == BTREE_AM_OID ||
            op_form->amopmethod == HASH_AM_OID)
        {
            if (op_in_opfamily(opno2, op_form->amopfamily))
            {
                result = true;
                break;
            }
        }
    }

    ReleaseSysCacheList(catlist);

    return result;
}


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

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

    tp = SearchSysCache4(AMPROCNUM,
                         ObjectIdGetDatum(opfamily),
                         ObjectIdGetDatum(lefttype),
                         ObjectIdGetDatum(righttype),
                         Int16GetDatum(procnum));
    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.
 */
char *
get_attname(Oid relid, AttrNumber attnum)
{
    HeapTuple   tp;

    tp = SearchSysCache2(ATTNUM,
                         ObjectIdGetDatum(relid),
                         Int16GetDatum(attnum));
    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_relid_attribute_name
 *
 * Same as above routine get_attname(), except that error
 * is handled by elog() instead of returning NULL.
 */
char *
get_relid_attribute_name(Oid relid, AttrNumber attnum)
{
    char       *attname;

    attname = get_attname(relid, attnum);
    if (attname == NULL)
        elog(ERROR, "cache lookup failed for attribute %d of relation %u",
             attnum, relid);
    return attname;
}

/*
 * 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 = SearchSysCache2(ATTNUM,
                         ObjectIdGetDatum(relid),
                         Int16GetDatum(attnum));
    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 = SearchSysCache2(ATTNUM,
                         ObjectIdGetDatum(relid),
                         Int16GetDatum(attnum));
    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_atttypetypmodcoll
 *
 *      A three-fer: given the relation id and the attribute number,
 *      fetch atttypid, atttypmod, and attcollation 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_atttypetypmodcoll(Oid relid, AttrNumber attnum,
                      Oid *typid, int32 *typmod, Oid *collid)
{
    HeapTuple   tp;
    Form_pg_attribute att_tup;

    tp = SearchSysCache2(ATTNUM,
                         ObjectIdGetDatum(relid),
                         Int16GetDatum(attnum));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for attribute %d of relation %u",
             attnum, relid);
    att_tup = (Form_pg_attribute) GETSTRUCT(tp);

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

/*              ---------- COLLATION CACHE ----------                    */

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

    tp = SearchSysCache1(COLLOID, ObjectIdGetDatum(colloid));
    if (HeapTupleIsValid(tp))
    {
        Form_pg_collation colltup = (Form_pg_collation) GETSTRUCT(tp);
        char       *result;

        result = pstrdup(NameStr(colltup->collname));
        ReleaseSysCache(tp);
        return result;
    }
    else
        return NULL;
}

/*              ---------- CONSTRAINT CACHE ----------                   */

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

    tp = SearchSysCache1(CONSTROID, ObjectIdGetDatum(conoid));
    if (HeapTupleIsValid(tp))
    {
        Form_pg_constraint contup = (Form_pg_constraint) GETSTRUCT(tp);
        char       *result;

        result = pstrdup(NameStr(contup->conname));
        ReleaseSysCache(tp);
        return result;
    }
    else
        return NULL;
}

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

/*
 * get_opclass_family
 *
 *      Returns the OID of the operator family the opclass belongs to.
 */
Oid
get_opclass_family(Oid opclass)
{
    HeapTuple   tp;
    Form_pg_opclass cla_tup;
    Oid         result;

    tp = SearchSysCache1(CLAOID, ObjectIdGetDatum(opclass));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for opclass %u", opclass);
    cla_tup = (Form_pg_opclass) GETSTRUCT(tp);

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

/*
 * get_opclass_input_type
 *
 *      Returns the OID of the datatype the opclass indexes.
 */
Oid
get_opclass_input_type(Oid opclass)
{
    HeapTuple   tp;
    Form_pg_opclass cla_tup;
    Oid         result;

    tp = SearchSysCache1(CLAOID, ObjectIdGetDatum(opclass));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for opclass %u", opclass);
    cla_tup = (Form_pg_opclass) GETSTRUCT(tp);

    result = cla_tup->opcintype;
    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 = SearchSysCache1(OPEROID, ObjectIdGetDatum(opno));
    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 = SearchSysCache1(OPEROID, ObjectIdGetDatum(opno));
    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_input_types
 *
 *      Returns the left and right input datatypes for an operator
 *      (InvalidOid if not relevant).
 */
void
op_input_types(Oid opno, Oid *lefttype, Oid *righttype)
{
    HeapTuple   tp;
    Form_pg_operator optup;

    tp = SearchSysCache1(OPEROID, ObjectIdGetDatum(opno));
    if (!HeapTupleIsValid(tp))  /* shouldn't happen */
        elog(ERROR, "cache lookup failed for operator %u", opno);
    optup = (Form_pg_operator) GETSTRUCT(tp);
    *lefttype = optup->oprleft;
    *righttype = optup->oprright;
    ReleaseSysCache(tp);
}

/*
 * op_mergejoinable
 *
 * Returns true if the operator is potentially mergejoinable.  (The planner
 * will fail to find any mergejoin plans unless there are suitable btree
 * opfamily entries for this operator and associated sortops.  The pg_operator
 * flag is just a hint to tell the planner whether to bother looking.)
 *
 * In some cases (currently only array_eq and record_eq), mergejoinability
 * depends on the specific input data type the operator is invoked for, so
 * that must be passed as well. We currently assume that only one input's type
 * is needed to check this --- by convention, pass the left input's data type.
 */
bool
op_mergejoinable(Oid opno, Oid inputtype)
{
    bool        result = false;
    HeapTuple   tp;
    TypeCacheEntry *typentry;

    /*
     * For array_eq or record_eq, we can sort if the element or field types
     * are all sortable.  We could implement all the checks for that here, but
     * the typcache already does that and caches the results too, so let's
     * rely on the typcache.
     */
    if (opno == ARRAY_EQ_OP)
    {
        typentry = lookup_type_cache(inputtype, TYPECACHE_CMP_PROC);
        if (typentry->cmp_proc == F_BTARRAYCMP)
            result = true;
    }
    else if (opno == RECORD_EQ_OP)
    {
        typentry = lookup_type_cache(inputtype, TYPECACHE_CMP_PROC);
        if (typentry->cmp_proc == F_BTRECORDCMP)
            result = true;
    }
    else
    {
        /* For all other operators, rely on pg_operator.oprcanmerge */
        tp = SearchSysCache1(OPEROID, ObjectIdGetDatum(opno));
        if (HeapTupleIsValid(tp))
        {
            Form_pg_operator optup = (Form_pg_operator) GETSTRUCT(tp);

            result = optup->oprcanmerge;
            ReleaseSysCache(tp);
        }
    }
    return result;
}

/*
 * op_hashjoinable
 *
 * Returns true if the operator is hashjoinable.  (There must be a suitable
 * hash opfamily entry for this operator if it is so marked.)
 *
 * In some cases (currently only array_eq), hashjoinability depends on the
 * specific input data type the operator is invoked for, so that must be
 * passed as well.  We currently assume that only one input's type is needed
 * to check this --- by convention, pass the left input's data type.
 */
bool
op_hashjoinable(Oid opno, Oid inputtype)
{
    bool        result = false;
    HeapTuple   tp;
    TypeCacheEntry *typentry;

    /* As in op_mergejoinable, let the typcache handle the hard cases */
    /* Eventually we'll need a similar case for record_eq ... */
    if (opno == ARRAY_EQ_OP)
    {
        typentry = lookup_type_cache(inputtype, TYPECACHE_HASH_PROC);
        if (typentry->hash_proc == F_HASH_ARRAY)
            result = true;
    }
    else
    {
        /* For all other operators, rely on pg_operator.oprcanhash */
        tp = SearchSysCache1(OPEROID, ObjectIdGetDatum(opno));
        if (HeapTupleIsValid(tp))
        {
            Form_pg_operator optup = (Form_pg_operator) GETSTRUCT(tp);

            result = optup->oprcanhash;
            ReleaseSysCache(tp);
        }
    }
    return result;
}

/*
 * op_strict
 *
 * Get the proisstrict flag for the operator's underlying function.
 */
bool
op_strict(Oid opno)
{
    RegProcedure funcid = get_opcode(opno);

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

    return func_strict((Oid) funcid);
}

/*
 * 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 %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 = SearchSysCache1(OPEROID, ObjectIdGetDatum(opno));
    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 = SearchSysCache1(OPEROID, ObjectIdGetDatum(opno));
    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 = SearchSysCache1(OPEROID, ObjectIdGetDatum(opno));
    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 = SearchSysCache1(OPEROID, ObjectIdGetDatum(opno));
    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 = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    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_namespace
 *
 *      Returns the pg_namespace OID associated with a given function.
 */
Oid
get_func_namespace(Oid funcid)
{
    HeapTuple   tp;

    tp = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    if (HeapTupleIsValid(tp))
    {
        Form_pg_proc functup = (Form_pg_proc) GETSTRUCT(tp);
        Oid         result;

        result = functup->pronamespace;
        ReleaseSysCache(tp);
        return result;
    }
    else
        return InvalidOid;
}

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

    tp = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for function %u", funcid);

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

/*
 * get_func_nargs
 *      Given procedure id, return the number of arguments.
 */
int
get_func_nargs(Oid funcid)
{
    HeapTuple   tp;
    int         result;

    tp = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for function %u", funcid);

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

/*
 * get_func_signature
 *      Given procedure id, return the function's argument and result types.
 *      (The return value is the result type.)
 *
 * The arguments are returned as a palloc'd array.
 */
Oid
get_func_signature(Oid funcid, Oid **argtypes, int *nargs)
{
    HeapTuple   tp;
    Form_pg_proc procstruct;
    Oid         result;

    tp = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for function %u", funcid);

    procstruct = (Form_pg_proc) GETSTRUCT(tp);

    result = procstruct->prorettype;
    *nargs = (int) procstruct->pronargs;
    Assert(*nargs == procstruct->proargtypes.dim1);
    *argtypes = (Oid *) palloc(*nargs * sizeof(Oid));
    memcpy(*argtypes, procstruct->proargtypes.values, *nargs * sizeof(Oid));

    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 = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for function %u", funcid);

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

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

    tp = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for function %u", funcid);

    result = ((Form_pg_proc) GETSTRUCT(tp))->proisstrict;
    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 = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for function %u", funcid);

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

/*
 * get_func_leakproof
 *     Given procedure id, return the function's leakproof field.
 */
bool
get_func_leakproof(Oid funcid)
{
    HeapTuple   tp;
    bool        result;

    tp = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for function %u", funcid);

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

/*
 * get_func_cost
 *      Given procedure id, return the function's procost field.
 */
float4
get_func_cost(Oid funcid)
{
    HeapTuple   tp;
    float4      result;

    tp = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for function %u", funcid);

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

/*
 * get_func_rows
 *      Given procedure id, return the function's prorows field.
 */
float4
get_func_rows(Oid funcid)
{
    HeapTuple   tp;
    float4      result;

    tp = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for function %u", funcid);

    result = ((Form_pg_proc) GETSTRUCT(tp))->prorows;
    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 GetSysCacheOid2(RELNAMENSP,
                           PointerGetDatum(relname),
                           ObjectIdGetDatum(relnamespace));
}

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

    tp = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
    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 = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
    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 = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
    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 = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
    if (HeapTupleIsValid(tp))
    {
        Form_pg_class reltup = (Form_pg_class) GETSTRUCT(tp);
        Oid         result;

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

/*
 * get_rel_relkind
 *
 *      Returns the relkind associated with a given relation.
 */
char
get_rel_relkind(Oid relid)
{
    HeapTuple   tp;

    tp = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
    if (HeapTupleIsValid(tp))
    {
        Form_pg_class reltup = (Form_pg_class) GETSTRUCT(tp);
        char        result;

        result = reltup->relkind;
        ReleaseSysCache(tp);
        return result;
    }
    else
        return '\0';
}

/*
 * get_rel_tablespace
 *
 *      Returns the pg_tablespace OID associated with a given relation.
 *
 * Note: InvalidOid might mean either that we couldn't find the relation,
 * or that it is in the database's default tablespace.
 */
Oid
get_rel_tablespace(Oid relid)
{
    HeapTuple   tp;

    tp = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
    if (HeapTupleIsValid(tp))
    {
        Form_pg_class reltup = (Form_pg_class) GETSTRUCT(tp);
        Oid         result;

        result = reltup->reltablespace;
        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 = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    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 = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    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 = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    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 = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    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 = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    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);
}

/*
 * getTypeIOParam
 *      Given a pg_type row, select the type OID to pass to I/O functions
 *
 * Formerly, all I/O functions were passed pg_type.typelem as their second
 * parameter, but we now have a more complex rule about what to pass.
 * This knowledge is intended to be centralized here --- direct references
 * to typelem elsewhere in the code are wrong, if they are associated with
 * I/O calls and not with actual subscripting operations!  (But see
 * bootstrap.c's boot_get_type_io_data() if you need to change this.)
 *
 * As of PostgreSQL 8.1, output functions receive only the value itself
 * and not any auxiliary parameters, so the name of this routine is now
 * a bit of a misnomer ... it should be getTypeInputParam.
 */
Oid
getTypeIOParam(HeapTuple typeTuple)
{
    Form_pg_type typeStruct = (Form_pg_type) GETSTRUCT(typeTuple);

    /*
     * Array types get their typelem as parameter; everybody else gets their
     * own type OID as parameter.
     */
    if (OidIsValid(typeStruct->typelem))
        return typeStruct->typelem;
    else
        return HeapTupleGetOid(typeTuple);
}

/*
 * get_type_io_data
 *
 *      A six-fer:  given the type OID, return typlen, typbyval, typalign,
 *                  typdelim, typioparam, and IO function OID. The IO function
 *                  returned is controlled by IOFuncSelector
 */
void
get_type_io_data(Oid typid,
                 IOFuncSelector which_func,
                 int16 *typlen,
                 bool *typbyval,
                 char *typalign,
                 char *typdelim,
                 Oid *typioparam,
                 Oid *func)
{
    HeapTuple   typeTuple;
    Form_pg_type typeStruct;

    /*
     * In bootstrap mode, pass it off to bootstrap.c.  This hack allows us to
     * use array_in and array_out during bootstrap.
     */
    if (IsBootstrapProcessingMode())
    {
        Oid         typinput;
        Oid         typoutput;

        boot_get_type_io_data(typid,
                              typlen,
                              typbyval,
                              typalign,
                              typdelim,
                              typioparam,
                              &typinput,
                              &typoutput);
        switch (which_func)
        {
            case IOFunc_input:
                *func = typinput;
                break;
            case IOFunc_output:
                *func = typoutput;
                break;
            default:
                elog(ERROR, "binary I/O not supported during bootstrap");
                break;
        }
        return;
    }

    typeTuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    if (!HeapTupleIsValid(typeTuple))
        elog(ERROR, "cache lookup failed for type %u", typid);
    typeStruct = (Form_pg_type) GETSTRUCT(typeTuple);

    *typlen = typeStruct->typlen;
    *typbyval = typeStruct->typbyval;
    *typalign = typeStruct->typalign;
    *typdelim = typeStruct->typdelim;
    *typioparam = getTypeIOParam(typeTuple);
    switch (which_func)
    {
        case IOFunc_input:
            *func = typeStruct->typinput;
            break;
        case IOFunc_output:
            *func = typeStruct->typoutput;
            break;
        case IOFunc_receive:
            *func = typeStruct->typreceive;
            break;
        case IOFunc_send:
            *func = typeStruct->typsend;
            break;
    }
    ReleaseSysCache(typeTuple);
}

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

    tp = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    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 = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    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 = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    if (!HeapTupleIsValid(typeTuple))
        elog(ERROR, "cache lookup failed for 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(TextDatumGetCString(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 = TextDatumGetCString(datum);
            /* Convert C string to a value of the given type */
            datum = OidInputFunctionCall(type->typinput, strDefaultVal,
                                         getTypeIOParam(typeTuple), -1);
            /* Build a Const node containing the value */
            expr = (Node *) makeConst(typid,
                                      -1,
                                      type->typcollation,
                                      type->typlen,
                                      datum,
                                      false,
                                      type->typbyval);
            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)
{
    int32       typmod = -1;

    return getBaseTypeAndTypmod(typid, &typmod);
}

/*
 * getBaseTypeAndTypmod
 *      If the given type is a domain, return its base type and typmod;
 *      otherwise return the type's own OID, and leave *typmod unchanged.
 *
 * Note that the "applied typmod" should be -1 for every domain level
 * above the bottommost; therefore, if the passed-in typid is indeed
 * a domain, *typmod should be -1.
 */
Oid
getBaseTypeAndTypmod(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 = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
        if (!HeapTupleIsValid(tup))
            elog(ERROR, "cache lookup failed for type %u", typid);
        typTup = (Form_pg_type) GETSTRUCT(tup);
        if (typTup->typtype != TYPTYPE_DOMAIN)
        {
            /* Not a domain, so done */
            ReleaseSysCache(tup);
            break;
        }

        Assert(*typmod == -1);
        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 = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    if (HeapTupleIsValid(tp))
    {
        Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
        char        result;

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

/*
 * type_is_rowtype
 *
 *      Convenience function to determine whether a type OID represents
 *      a "rowtype" type --- either RECORD or a named composite type.
 */
bool
type_is_rowtype(Oid typid)
{
    return (typid == RECORDOID || get_typtype(typid) == TYPTYPE_COMPOSITE);
}

/*
 * type_is_enum
 *    Returns true if the given type is an enum type.
 */
bool
type_is_enum(Oid typid)
{
    return (get_typtype(typid) == TYPTYPE_ENUM);
}

/*
 * type_is_range
 *    Returns true if the given type is a range type.
 */
bool
type_is_range(Oid typid)
{
    return (get_typtype(typid) == TYPTYPE_RANGE);
}

/*
 * get_type_category_preferred
 *
 *      Given the type OID, fetch its category and preferred-type status.
 *      Throws error on failure.
 */
void
get_type_category_preferred(Oid typid, char *typcategory, bool *typispreferred)
{
    HeapTuple   tp;
    Form_pg_type typtup;

    tp = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for type %u", typid);
    typtup = (Form_pg_type) GETSTRUCT(tp);
    *typcategory = typtup->typcategory;
    *typispreferred = typtup->typispreferred;
    ReleaseSysCache(tp);
}

/*
 * get_typ_typrelid
 *
 *      Given the type OID, get the typrelid (InvalidOid if not a complex
 *      type).
 */
Oid
get_typ_typrelid(Oid typid)
{
    HeapTuple   tp;

    tp = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    if (HeapTupleIsValid(tp))
    {
        Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
        Oid         result;

        result = typtup->typrelid;
        ReleaseSysCache(tp);
        return result;
    }
    else
        return InvalidOid;
}

/*
 * get_element_type
 *
 *      Given the type OID, get the typelem (InvalidOid if not an array type).
 *
 * NB: this only considers varlena arrays to be true arrays; InvalidOid is
 * returned if the input is a fixed-length array type.
 */
Oid
get_element_type(Oid typid)
{
    HeapTuple   tp;

    tp = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    if (HeapTupleIsValid(tp))
    {
        Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
        Oid         result;

        if (typtup->typlen == -1)
            result = typtup->typelem;
        else
            result = InvalidOid;
        ReleaseSysCache(tp);
        return result;
    }
    else
        return InvalidOid;
}

/*
 * get_array_type
 *
 *      Given the type OID, get the corresponding "true" array type.
 *      Returns InvalidOid if no array type can be found.
 */
Oid
get_array_type(Oid typid)
{
    HeapTuple   tp;
    Oid         result = InvalidOid;

    tp = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    if (HeapTupleIsValid(tp))
    {
        result = ((Form_pg_type) GETSTRUCT(tp))->typarray;
        ReleaseSysCache(tp);
    }
    return result;
}

/*
 * get_base_element_type
 *      Given the type OID, get the typelem, looking "through" any domain
 *      to its underlying array type.
 *
 * This is equivalent to get_element_type(getBaseType(typid)), but avoids
 * an extra cache lookup.  Note that it fails to provide any information
 * about the typmod of the array.
 */
Oid
get_base_element_type(Oid typid)
{
    /*
     * We loop to find the bottom base type in a stack of domains.
     */
    for (;;)
    {
        HeapTuple   tup;
        Form_pg_type typTup;

        tup = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
        if (!HeapTupleIsValid(tup))
            break;
        typTup = (Form_pg_type) GETSTRUCT(tup);
        if (typTup->typtype != TYPTYPE_DOMAIN)
        {
            /* Not a domain, so stop descending */
            Oid         result;

            /* This test must match get_element_type */
            if (typTup->typlen == -1)
                result = typTup->typelem;
            else
                result = InvalidOid;
            ReleaseSysCache(tup);
            return result;
        }

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

    /* Like get_element_type, silently return InvalidOid for bogus input */
    return InvalidOid;
}

/*
 * getTypeInputInfo
 *
 *      Get info needed for converting values of a type to internal form
 */
void
getTypeInputInfo(Oid type, Oid *typInput, Oid *typIOParam)
{
    HeapTuple   typeTuple;
    Form_pg_type pt;

    typeTuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(type));
    if (!HeapTupleIsValid(typeTuple))
        elog(ERROR, "cache lookup failed for type %u", type);
    pt = (Form_pg_type) GETSTRUCT(typeTuple);

    if (!pt->typisdefined)
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("type %s is only a shell",
                        format_type_be(type))));
    if (!OidIsValid(pt->typinput))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_FUNCTION),
                 errmsg("no input function available for type %s",
                        format_type_be(type))));

    *typInput = pt->typinput;
    *typIOParam = getTypeIOParam(typeTuple);

    ReleaseSysCache(typeTuple);
}

/*
 * getTypeOutputInfo
 *
 *      Get info needed for printing values of a type
 */
void
getTypeOutputInfo(Oid type, Oid *typOutput, bool *typIsVarlena)
{
    HeapTuple   typeTuple;
    Form_pg_type pt;

    typeTuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(type));
    if (!HeapTupleIsValid(typeTuple))
        elog(ERROR, "cache lookup failed for type %u", type);
    pt = (Form_pg_type) GETSTRUCT(typeTuple);

    if (!pt->typisdefined)
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("type %s is only a shell",
                        format_type_be(type))));
    if (!OidIsValid(pt->typoutput))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_FUNCTION),
                 errmsg("no output function available for type %s",
                        format_type_be(type))));

    *typOutput = pt->typoutput;
    *typIsVarlena = (!pt->typbyval) && (pt->typlen == -1);

    ReleaseSysCache(typeTuple);
}

/*
 * getTypeBinaryInputInfo
 *
 *      Get info needed for binary input of values of a type
 */
void
getTypeBinaryInputInfo(Oid type, Oid *typReceive, Oid *typIOParam)
{
    HeapTuple   typeTuple;
    Form_pg_type pt;

    typeTuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(type));
    if (!HeapTupleIsValid(typeTuple))
        elog(ERROR, "cache lookup failed for type %u", type);
    pt = (Form_pg_type) GETSTRUCT(typeTuple);

    if (!pt->typisdefined)
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("type %s is only a shell",
                        format_type_be(type))));
    if (!OidIsValid(pt->typreceive))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_FUNCTION),
                 errmsg("no binary input function available for type %s",
                        format_type_be(type))));

    *typReceive = pt->typreceive;
    *typIOParam = getTypeIOParam(typeTuple);

    ReleaseSysCache(typeTuple);
}

/*
 * getTypeBinaryOutputInfo
 *
 *      Get info needed for binary output of values of a type
 */
void
getTypeBinaryOutputInfo(Oid type, Oid *typSend, bool *typIsVarlena)
{
    HeapTuple   typeTuple;
    Form_pg_type pt;

    typeTuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(type));
    if (!HeapTupleIsValid(typeTuple))
        elog(ERROR, "cache lookup failed for type %u", type);
    pt = (Form_pg_type) GETSTRUCT(typeTuple);

    if (!pt->typisdefined)
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("type %s is only a shell",
                        format_type_be(type))));
    if (!OidIsValid(pt->typsend))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_FUNCTION),
                 errmsg("no binary output function available for type %s",
                        format_type_be(type))));

    *typSend = pt->typsend;
    *typIsVarlena = (!pt->typbyval) && (pt->typlen == -1);

    ReleaseSysCache(typeTuple);
}

/*
 * get_typmodin
 *
 *      Given the type OID, return the type's typmodin procedure, if any.
 */
Oid
get_typmodin(Oid typid)
{
    HeapTuple   tp;

    tp = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    if (HeapTupleIsValid(tp))
    {
        Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
        Oid         result;

        result = typtup->typmodin;
        ReleaseSysCache(tp);
        return result;
    }
    else
        return InvalidOid;
}

#ifdef NOT_USED
/*
 * get_typmodout
 *
 *      Given the type OID, return the type's typmodout procedure, if any.
 */
Oid
get_typmodout(Oid typid)
{
    HeapTuple   tp;

    tp = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    if (HeapTupleIsValid(tp))
    {
        Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
        Oid         result;

        result = typtup->typmodout;
        ReleaseSysCache(tp);
        return result;
    }
    else
        return InvalidOid;
}
#endif   /* NOT_USED */

/*
 * get_typcollation
 *
 *      Given the type OID, return the type's typcollation attribute.
 */
Oid
get_typcollation(Oid typid)
{
    HeapTuple   tp;

    tp = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
    if (HeapTupleIsValid(tp))
    {
        Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
        Oid         result;

        result = typtup->typcollation;
        ReleaseSysCache(tp);
        return result;
    }
    else
        return InvalidOid;
}


/*
 * type_is_collatable
 *
 *      Return whether the type cares about collations
 */
bool
type_is_collatable(Oid typid)
{
    return OidIsValid(get_typcollation(typid));
}


/*              ---------- 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.
 *
 * Currently this is only consulted for individual tables, not for inheritance
 * trees, so we don't need an "inh" parameter.
 *
 * Calling a hook at this point looks somewhat strange, but is required
 * because the optimizer calls this function without any other way for
 * plug-ins to control the result.
 */
int32
get_attavgwidth(Oid relid, AttrNumber attnum)
{
    HeapTuple   tp;
    int32       stawidth;

    if (get_attavgwidth_hook)
    {
        stawidth = (*get_attavgwidth_hook) (relid, attnum);
        if (stawidth > 0)
            return stawidth;
    }
    tp = SearchSysCache3(STATRELATTINH,
                         ObjectIdGetDatum(relid),
                         Int16GetDatum(attnum),
                         BoolGetDatum(false));
    if (HeapTupleIsValid(tp))
    {
        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.
 * Also, this API allows this routine to be used with statistics tuples
 * that have been provided by a stats hook and didn't really come from
 * pg_statistic.
 *
 * statstuple: pg_statistics tuple to be examined.
 * atttype: type OID of attribute (can be InvalidOid if values == NULL).
 * atttypmod: typmod of attribute (can be 0 if values == NULL).
 * reqkind: STAKIND code for desired statistics slot kind.
 * reqop: STAOP value wanted, or InvalidOid if don't care.
 * actualop: if not NULL, *actualop receives the actual STAOP value.
 * 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.
 *
 * Note: at present, atttype/atttypmod aren't actually used here at all.
 * But the caller must have the correct (or at least binary-compatible)
 * type ID to pass to free_attstatsslot later.
 */
bool
get_attstatsslot(HeapTuple statstuple,
                 Oid atttype, int32 atttypmod,
                 int reqkind, Oid reqop,
                 Oid *actualop,
                 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;
    Oid         arrayelemtype;
    int         narrayelem;
    HeapTuple   typeTuple;
    Form_pg_type typeForm;

    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 (actualop)
        *actualop = (&stats->staop1)[i];

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

        /*
         * Need to get info about the array element type.  We look at the
         * actual element type embedded in the array, which might be only
         * binary-compatible with the passed-in atttype.  The info we extract
         * here should be the same either way, but deconstruct_array is picky
         * about having an exact type OID match.
         */
        arrayelemtype = ARR_ELEMTYPE(statarray);
        typeTuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(arrayelemtype));
        if (!HeapTupleIsValid(typeTuple))
            elog(ERROR, "cache lookup failed for type %u", arrayelemtype);
        typeForm = (Form_pg_type) GETSTRUCT(typeTuple);

        /* Deconstruct array into Datum elements; NULLs not expected */
        deconstruct_array(statarray,
                          arrayelemtype,
                          typeForm->typlen,
                          typeForm->typbyval,
                          typeForm->typalign,
                          values, NULL, nvalues);

        /*
         * If the element type is pass-by-reference, we now have a bunch of
         * Datums that are pointers into the syscache value.  Copy them to
         * avoid problems if syscache decides to drop the entry.
         */
        if (!typeForm->typbyval)
        {
            for (j = 0; j < *nvalues; j++)
            {
                (*values)[j] = datumCopy((*values)[j],
                                         typeForm->typbyval,
                                         typeForm->typlen);
            }
        }

        ReleaseSysCache(typeTuple);

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

    if (numbers)
    {
        val = SysCacheGetAttr(STATRELATTINH, statstuple,
                              Anum_pg_statistic_stanumbers1 + i,
                              &isnull);
        if (isnull)
            elog(ERROR, "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_HASNULL(statarray) ||
            ARR_ELEMTYPE(statarray) != FLOAT4OID)
            elog(ERROR, "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;
}

/*
 * free_attstatsslot
 *      Free data allocated by get_attstatsslot
 *
 * atttype need be valid only if values != NULL.
 */
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 = SearchSysCache1(NAMESPACEOID, ObjectIdGetDatum(nspid));
    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_RANGE CACHE ----------                 */

/*
 * get_range_subtype
 *      Returns the subtype of a given range type
 *
 * Returns InvalidOid if the type is not a range type.
 */
Oid
get_range_subtype(Oid rangeOid)
{
    HeapTuple   tp;

    tp = SearchSysCache1(RANGETYPE, ObjectIdGetDatum(rangeOid));
    if (HeapTupleIsValid(tp))
    {
        Form_pg_range rngtup = (Form_pg_range) GETSTRUCT(tp);
        Oid         result;

        result = rngtup->rngsubtype;
        ReleaseSysCache(tp);
        return result;
    }
    else
        return InvalidOid;
}