funcapi.c

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/*-------------------------------------------------------------------------
 *
 * funcapi.c
 *    Utility and convenience functions for fmgr functions that return
 *    sets and/or composite types.
 *
 * Copyright (c) 2002-2013, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/backend/utils/fmgr/funcapi.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/htup_details.h"
#include "catalog/namespace.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "nodes/nodeFuncs.h"
#include "parser/parse_coerce.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/syscache.h"
#include "utils/typcache.h"


static void shutdown_MultiFuncCall(Datum arg);
static TypeFuncClass internal_get_result_type(Oid funcid,
                         Node *call_expr,
                         ReturnSetInfo *rsinfo,
                         Oid *resultTypeId,
                         TupleDesc *resultTupleDesc);
static bool resolve_polymorphic_tupdesc(TupleDesc tupdesc,
                            oidvector *declared_args,
                            Node *call_expr);
static TypeFuncClass get_type_func_class(Oid typid);


/*
 * init_MultiFuncCall
 * Create an empty FuncCallContext data structure
 * and do some other basic Multi-function call setup
 * and error checking
 */
FuncCallContext *
init_MultiFuncCall(PG_FUNCTION_ARGS)
{
    FuncCallContext *retval;

    /*
     * Bail if we're called in the wrong context
     */
    if (fcinfo->resultinfo == NULL || !IsA(fcinfo->resultinfo, ReturnSetInfo))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("set-valued function called in context that cannot accept a set")));

    if (fcinfo->flinfo->fn_extra == NULL)
    {
        /*
         * First call
         */
        ReturnSetInfo *rsi = (ReturnSetInfo *) fcinfo->resultinfo;
        MemoryContext multi_call_ctx;

        /*
         * Create a suitably long-lived context to hold cross-call data
         */
        multi_call_ctx = AllocSetContextCreate(fcinfo->flinfo->fn_mcxt,
                                               "SRF multi-call context",
                                               ALLOCSET_SMALL_MINSIZE,
                                               ALLOCSET_SMALL_INITSIZE,
                                               ALLOCSET_SMALL_MAXSIZE);

        /*
         * Allocate suitably long-lived space and zero it
         */
        retval = (FuncCallContext *)
            MemoryContextAllocZero(multi_call_ctx,
                                   sizeof(FuncCallContext));

        /*
         * initialize the elements
         */
        retval->call_cntr = 0;
        retval->max_calls = 0;
        retval->slot = NULL;
        retval->user_fctx = NULL;
        retval->attinmeta = NULL;
        retval->tuple_desc = NULL;
        retval->multi_call_memory_ctx = multi_call_ctx;

        /*
         * save the pointer for cross-call use
         */
        fcinfo->flinfo->fn_extra = retval;

        /*
         * Ensure we will get shut down cleanly if the exprcontext is not run
         * to completion.
         */
        RegisterExprContextCallback(rsi->econtext,
                                    shutdown_MultiFuncCall,
                                    PointerGetDatum(fcinfo->flinfo));
    }
    else
    {
        /* second and subsequent calls */
        elog(ERROR, "init_MultiFuncCall cannot be called more than once");

        /* never reached, but keep compiler happy */
        retval = NULL;
    }

    return retval;
}

/*
 * per_MultiFuncCall
 *
 * Do Multi-function per-call setup
 */
FuncCallContext *
per_MultiFuncCall(PG_FUNCTION_ARGS)
{
    FuncCallContext *retval = (FuncCallContext *) fcinfo->flinfo->fn_extra;

    /*
     * Clear the TupleTableSlot, if present.  This is for safety's sake: the
     * Slot will be in a long-lived context (it better be, if the
     * FuncCallContext is pointing to it), but in most usage patterns the
     * tuples stored in it will be in the function's per-tuple context. So at
     * the beginning of each call, the Slot will hold a dangling pointer to an
     * already-recycled tuple.  We clear it out here.
     *
     * Note: use of retval->slot is obsolete as of 8.0, and we expect that it
     * will always be NULL.  This is just here for backwards compatibility in
     * case someone creates a slot anyway.
     */
    if (retval->slot != NULL)
        ExecClearTuple(retval->slot);

    return retval;
}

/*
 * end_MultiFuncCall
 * Clean up after init_MultiFuncCall
 */
void
end_MultiFuncCall(PG_FUNCTION_ARGS, FuncCallContext *funcctx)
{
    ReturnSetInfo *rsi = (ReturnSetInfo *) fcinfo->resultinfo;

    /* Deregister the shutdown callback */
    UnregisterExprContextCallback(rsi->econtext,
                                  shutdown_MultiFuncCall,
                                  PointerGetDatum(fcinfo->flinfo));

    /* But use it to do the real work */
    shutdown_MultiFuncCall(PointerGetDatum(fcinfo->flinfo));
}

/*
 * shutdown_MultiFuncCall
 * Shutdown function to clean up after init_MultiFuncCall
 */
static void
shutdown_MultiFuncCall(Datum arg)
{
    FmgrInfo   *flinfo = (FmgrInfo *) DatumGetPointer(arg);
    FuncCallContext *funcctx = (FuncCallContext *) flinfo->fn_extra;

    /* unbind from flinfo */
    flinfo->fn_extra = NULL;

    /*
     * Delete context that holds all multi-call data, including the
     * FuncCallContext itself
     */
    MemoryContextDelete(funcctx->multi_call_memory_ctx);
}


/*
 * get_call_result_type
 *      Given a function's call info record, determine the kind of datatype
 *      it is supposed to return.  If resultTypeId isn't NULL, *resultTypeId
 *      receives the actual datatype OID (this is mainly useful for scalar
 *      result types).  If resultTupleDesc isn't NULL, *resultTupleDesc
 *      receives a pointer to a TupleDesc when the result is of a composite
 *      type, or NULL when it's a scalar result.
 *
 * One hard case that this handles is resolution of actual rowtypes for
 * functions returning RECORD (from either the function's OUT parameter
 * list, or a ReturnSetInfo context node).  TYPEFUNC_RECORD is returned
 * only when we couldn't resolve the actual rowtype for lack of information.
 *
 * The other hard case that this handles is resolution of polymorphism.
 * We will never return polymorphic pseudotypes (ANYELEMENT etc), either
 * as a scalar result type or as a component of a rowtype.
 *
 * This function is relatively expensive --- in a function returning set,
 * try to call it only the first time through.
 */
TypeFuncClass
get_call_result_type(FunctionCallInfo fcinfo,
                     Oid *resultTypeId,
                     TupleDesc *resultTupleDesc)
{
    return internal_get_result_type(fcinfo->flinfo->fn_oid,
                                    fcinfo->flinfo->fn_expr,
                                    (ReturnSetInfo *) fcinfo->resultinfo,
                                    resultTypeId,
                                    resultTupleDesc);
}

/*
 * get_expr_result_type
 *      As above, but work from a calling expression node tree
 */
TypeFuncClass
get_expr_result_type(Node *expr,
                     Oid *resultTypeId,
                     TupleDesc *resultTupleDesc)
{
    TypeFuncClass result;

    if (expr && IsA(expr, FuncExpr))
        result = internal_get_result_type(((FuncExpr *) expr)->funcid,
                                          expr,
                                          NULL,
                                          resultTypeId,
                                          resultTupleDesc);
    else if (expr && IsA(expr, OpExpr))
        result = internal_get_result_type(get_opcode(((OpExpr *) expr)->opno),
                                          expr,
                                          NULL,
                                          resultTypeId,
                                          resultTupleDesc);
    else
    {
        /* handle as a generic expression; no chance to resolve RECORD */
        Oid         typid = exprType(expr);

        if (resultTypeId)
            *resultTypeId = typid;
        if (resultTupleDesc)
            *resultTupleDesc = NULL;
        result = get_type_func_class(typid);
        if (result == TYPEFUNC_COMPOSITE && resultTupleDesc)
            *resultTupleDesc = lookup_rowtype_tupdesc_copy(typid, -1);
    }

    return result;
}

/*
 * get_func_result_type
 *      As above, but work from a function's OID only
 *
 * This will not be able to resolve pure-RECORD results nor polymorphism.
 */
TypeFuncClass
get_func_result_type(Oid functionId,
                     Oid *resultTypeId,
                     TupleDesc *resultTupleDesc)
{
    return internal_get_result_type(functionId,
                                    NULL,
                                    NULL,
                                    resultTypeId,
                                    resultTupleDesc);
}

/*
 * internal_get_result_type -- workhorse code implementing all the above
 *
 * funcid must always be supplied.  call_expr and rsinfo can be NULL if not
 * available.  We will return TYPEFUNC_RECORD, and store NULL into
 * *resultTupleDesc, if we cannot deduce the complete result rowtype from
 * the available information.
 */
static TypeFuncClass
internal_get_result_type(Oid funcid,
                         Node *call_expr,
                         ReturnSetInfo *rsinfo,
                         Oid *resultTypeId,
                         TupleDesc *resultTupleDesc)
{
    TypeFuncClass result;
    HeapTuple   tp;
    Form_pg_proc procform;
    Oid         rettype;
    TupleDesc   tupdesc;

    /* First fetch the function's pg_proc row to inspect its rettype */
    tp = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    if (!HeapTupleIsValid(tp))
        elog(ERROR, "cache lookup failed for function %u", funcid);
    procform = (Form_pg_proc) GETSTRUCT(tp);

    rettype = procform->prorettype;

    /* Check for OUT parameters defining a RECORD result */
    tupdesc = build_function_result_tupdesc_t(tp);
    if (tupdesc)
    {
        /*
         * It has OUT parameters, so it's basically like a regular composite
         * type, except we have to be able to resolve any polymorphic OUT
         * parameters.
         */
        if (resultTypeId)
            *resultTypeId = rettype;

        if (resolve_polymorphic_tupdesc(tupdesc,
                                        &procform->proargtypes,
                                        call_expr))
        {
            if (tupdesc->tdtypeid == RECORDOID &&
                tupdesc->tdtypmod < 0)
                assign_record_type_typmod(tupdesc);
            if (resultTupleDesc)
                *resultTupleDesc = tupdesc;
            result = TYPEFUNC_COMPOSITE;
        }
        else
        {
            if (resultTupleDesc)
                *resultTupleDesc = NULL;
            result = TYPEFUNC_RECORD;
        }

        ReleaseSysCache(tp);

        return result;
    }

    /*
     * If scalar polymorphic result, try to resolve it.
     */
    if (IsPolymorphicType(rettype))
    {
        Oid         newrettype = exprType(call_expr);

        if (newrettype == InvalidOid)   /* this probably should not happen */
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("could not determine actual result type for function \"%s\" declared to return type %s",
                            NameStr(procform->proname),
                            format_type_be(rettype))));
        rettype = newrettype;
    }

    if (resultTypeId)
        *resultTypeId = rettype;
    if (resultTupleDesc)
        *resultTupleDesc = NULL;    /* default result */

    /* Classify the result type */
    result = get_type_func_class(rettype);
    switch (result)
    {
        case TYPEFUNC_COMPOSITE:
            if (resultTupleDesc)
                *resultTupleDesc = lookup_rowtype_tupdesc_copy(rettype, -1);
            /* Named composite types can't have any polymorphic columns */
            break;
        case TYPEFUNC_SCALAR:
            break;
        case TYPEFUNC_RECORD:
            /* We must get the tupledesc from call context */
            if (rsinfo && IsA(rsinfo, ReturnSetInfo) &&
                rsinfo->expectedDesc != NULL)
            {
                result = TYPEFUNC_COMPOSITE;
                if (resultTupleDesc)
                    *resultTupleDesc = rsinfo->expectedDesc;
                /* Assume no polymorphic columns here, either */
            }
            break;
        default:
            break;
    }

    ReleaseSysCache(tp);

    return result;
}

/*
 * Given the result tuple descriptor for a function with OUT parameters,
 * replace any polymorphic columns (ANYELEMENT etc) with correct data types
 * deduced from the input arguments. Returns TRUE if able to deduce all types,
 * FALSE if not.
 */
static bool
resolve_polymorphic_tupdesc(TupleDesc tupdesc, oidvector *declared_args,
                            Node *call_expr)
{
    int         natts = tupdesc->natts;
    int         nargs = declared_args->dim1;
    bool        have_anyelement_result = false;
    bool        have_anyarray_result = false;
    bool        have_anyrange_result = false;
    bool        have_anynonarray = false;
    bool        have_anyenum = false;
    Oid         anyelement_type = InvalidOid;
    Oid         anyarray_type = InvalidOid;
    Oid         anyrange_type = InvalidOid;
    Oid         anycollation = InvalidOid;
    int         i;

    /* See if there are any polymorphic outputs; quick out if not */
    for (i = 0; i < natts; i++)
    {
        switch (tupdesc->attrs[i]->atttypid)
        {
            case ANYELEMENTOID:
                have_anyelement_result = true;
                break;
            case ANYARRAYOID:
                have_anyarray_result = true;
                break;
            case ANYNONARRAYOID:
                have_anyelement_result = true;
                have_anynonarray = true;
                break;
            case ANYENUMOID:
                have_anyelement_result = true;
                have_anyenum = true;
                break;
            case ANYRANGEOID:
                have_anyrange_result = true;
                break;
            default:
                break;
        }
    }
    if (!have_anyelement_result && !have_anyarray_result &&
        !have_anyrange_result)
        return true;

    /*
     * Otherwise, extract actual datatype(s) from input arguments.  (We assume
     * the parser already validated consistency of the arguments.)
     */
    if (!call_expr)
        return false;           /* no hope */

    for (i = 0; i < nargs; i++)
    {
        switch (declared_args->values[i])
        {
            case ANYELEMENTOID:
            case ANYNONARRAYOID:
            case ANYENUMOID:
                if (!OidIsValid(anyelement_type))
                    anyelement_type = get_call_expr_argtype(call_expr, i);
                break;
            case ANYARRAYOID:
                if (!OidIsValid(anyarray_type))
                    anyarray_type = get_call_expr_argtype(call_expr, i);
                break;
            case ANYRANGEOID:
                if (!OidIsValid(anyrange_type))
                    anyrange_type = get_call_expr_argtype(call_expr, i);
                break;
            default:
                break;
        }
    }

    /* If nothing found, parser messed up */
    if (!OidIsValid(anyelement_type) && !OidIsValid(anyarray_type) &&
        !OidIsValid(anyrange_type))
        return false;

    /* If needed, deduce one polymorphic type from others */
    if (have_anyelement_result && !OidIsValid(anyelement_type))
    {
        if (OidIsValid(anyarray_type))
            anyelement_type = resolve_generic_type(ANYELEMENTOID,
                                                   anyarray_type,
                                                   ANYARRAYOID);
        if (OidIsValid(anyrange_type))
        {
            Oid         subtype = resolve_generic_type(ANYELEMENTOID,
                                                       anyrange_type,
                                                       ANYRANGEOID);

            /* check for inconsistent array and range results */
            if (OidIsValid(anyelement_type) && anyelement_type != subtype)
                return false;
            anyelement_type = subtype;
        }
    }

    if (have_anyarray_result && !OidIsValid(anyarray_type))
        anyarray_type = resolve_generic_type(ANYARRAYOID,
                                             anyelement_type,
                                             ANYELEMENTOID);

    /*
     * We can't deduce a range type from other polymorphic inputs, because
     * there may be multiple range types for the same subtype.
     */
    if (have_anyrange_result && !OidIsValid(anyrange_type))
        return false;

    /* Enforce ANYNONARRAY if needed */
    if (have_anynonarray && type_is_array(anyelement_type))
        return false;

    /* Enforce ANYENUM if needed */
    if (have_anyenum && !type_is_enum(anyelement_type))
        return false;

    /*
     * Identify the collation to use for polymorphic OUT parameters. (It'll
     * necessarily be the same for both anyelement and anyarray.)  Note that
     * range types are not collatable, so any possible internal collation of a
     * range type is not considered here.
     */
    if (OidIsValid(anyelement_type))
        anycollation = get_typcollation(anyelement_type);
    else if (OidIsValid(anyarray_type))
        anycollation = get_typcollation(anyarray_type);

    if (OidIsValid(anycollation))
    {
        /*
         * The types are collatable, so consider whether to use a nondefault
         * collation.  We do so if we can identify the input collation used
         * for the function.
         */
        Oid         inputcollation = exprInputCollation(call_expr);

        if (OidIsValid(inputcollation))
            anycollation = inputcollation;
    }

    /* And finally replace the tuple column types as needed */
    for (i = 0; i < natts; i++)
    {
        switch (tupdesc->attrs[i]->atttypid)
        {
            case ANYELEMENTOID:
            case ANYNONARRAYOID:
            case ANYENUMOID:
                TupleDescInitEntry(tupdesc, i + 1,
                                   NameStr(tupdesc->attrs[i]->attname),
                                   anyelement_type,
                                   -1,
                                   0);
                TupleDescInitEntryCollation(tupdesc, i + 1, anycollation);
                break;
            case ANYARRAYOID:
                TupleDescInitEntry(tupdesc, i + 1,
                                   NameStr(tupdesc->attrs[i]->attname),
                                   anyarray_type,
                                   -1,
                                   0);
                TupleDescInitEntryCollation(tupdesc, i + 1, anycollation);
                break;
            case ANYRANGEOID:
                TupleDescInitEntry(tupdesc, i + 1,
                                   NameStr(tupdesc->attrs[i]->attname),
                                   anyrange_type,
                                   -1,
                                   0);
                /* no collation should be attached to a range type */
                break;
            default:
                break;
        }
    }

    return true;
}

/*
 * Given the declared argument types and modes for a function, replace any
 * polymorphic types (ANYELEMENT etc) with correct data types deduced from the
 * input arguments.  Returns TRUE if able to deduce all types, FALSE if not.
 * This is the same logic as resolve_polymorphic_tupdesc, but with a different
 * argument representation.
 *
 * argmodes may be NULL, in which case all arguments are assumed to be IN mode.
 */
bool
resolve_polymorphic_argtypes(int numargs, Oid *argtypes, char *argmodes,
                             Node *call_expr)
{
    bool        have_anyelement_result = false;
    bool        have_anyarray_result = false;
    bool        have_anyrange_result = false;
    Oid         anyelement_type = InvalidOid;
    Oid         anyarray_type = InvalidOid;
    Oid         anyrange_type = InvalidOid;
    int         inargno;
    int         i;

    /* First pass: resolve polymorphic inputs, check for outputs */
    inargno = 0;
    for (i = 0; i < numargs; i++)
    {
        char        argmode = argmodes ? argmodes[i] : PROARGMODE_IN;

        switch (argtypes[i])
        {
            case ANYELEMENTOID:
            case ANYNONARRAYOID:
            case ANYENUMOID:
                if (argmode == PROARGMODE_OUT || argmode == PROARGMODE_TABLE)
                    have_anyelement_result = true;
                else
                {
                    if (!OidIsValid(anyelement_type))
                    {
                        anyelement_type = get_call_expr_argtype(call_expr,
                                                                inargno);
                        if (!OidIsValid(anyelement_type))
                            return false;
                    }
                    argtypes[i] = anyelement_type;
                }
                break;
            case ANYARRAYOID:
                if (argmode == PROARGMODE_OUT || argmode == PROARGMODE_TABLE)
                    have_anyarray_result = true;
                else
                {
                    if (!OidIsValid(anyarray_type))
                    {
                        anyarray_type = get_call_expr_argtype(call_expr,
                                                              inargno);
                        if (!OidIsValid(anyarray_type))
                            return false;
                    }
                    argtypes[i] = anyarray_type;
                }
                break;
            case ANYRANGEOID:
                if (argmode == PROARGMODE_OUT || argmode == PROARGMODE_TABLE)
                    have_anyrange_result = true;
                else
                {
                    if (!OidIsValid(anyrange_type))
                    {
                        anyrange_type = get_call_expr_argtype(call_expr,
                                                              inargno);
                        if (!OidIsValid(anyrange_type))
                            return false;
                    }
                    argtypes[i] = anyrange_type;
                }
                break;
            default:
                break;
        }
        if (argmode != PROARGMODE_OUT && argmode != PROARGMODE_TABLE)
            inargno++;
    }

    /* Done? */
    if (!have_anyelement_result && !have_anyarray_result &&
        !have_anyrange_result)
        return true;

    /* If no input polymorphics, parser messed up */
    if (!OidIsValid(anyelement_type) && !OidIsValid(anyarray_type) &&
        !OidIsValid(anyrange_type))
        return false;

    /* If needed, deduce one polymorphic type from others */
    if (have_anyelement_result && !OidIsValid(anyelement_type))
    {
        if (OidIsValid(anyarray_type))
            anyelement_type = resolve_generic_type(ANYELEMENTOID,
                                                   anyarray_type,
                                                   ANYARRAYOID);
        if (OidIsValid(anyrange_type))
        {
            Oid         subtype = resolve_generic_type(ANYELEMENTOID,
                                                       anyrange_type,
                                                       ANYRANGEOID);

            /* check for inconsistent array and range results */
            if (OidIsValid(anyelement_type) && anyelement_type != subtype)
                return false;
            anyelement_type = subtype;
        }
    }

    if (have_anyarray_result && !OidIsValid(anyarray_type))
        anyarray_type = resolve_generic_type(ANYARRAYOID,
                                             anyelement_type,
                                             ANYELEMENTOID);

    /*
     * We can't deduce a range type from other polymorphic inputs, because
     * there may be multiple range types for the same subtype.
     */
    if (have_anyrange_result && !OidIsValid(anyrange_type))
        return false;

    /* XXX do we need to enforce ANYNONARRAY or ANYENUM here?  I think not */

    /* And finally replace the output column types as needed */
    for (i = 0; i < numargs; i++)
    {
        switch (argtypes[i])
        {
            case ANYELEMENTOID:
            case ANYNONARRAYOID:
            case ANYENUMOID:
                argtypes[i] = anyelement_type;
                break;
            case ANYARRAYOID:
                argtypes[i] = anyarray_type;
                break;
            case ANYRANGEOID:
                argtypes[i] = anyrange_type;
                break;
            default:
                break;
        }
    }

    return true;
}

/*
 * get_type_func_class
 *      Given the type OID, obtain its TYPEFUNC classification.
 *
 * This is intended to centralize a bunch of formerly ad-hoc code for
 * classifying types.  The categories used here are useful for deciding
 * how to handle functions returning the datatype.
 */
static TypeFuncClass
get_type_func_class(Oid typid)
{
    switch (get_typtype(typid))
    {
        case TYPTYPE_COMPOSITE:
            return TYPEFUNC_COMPOSITE;
        case TYPTYPE_BASE:
        case TYPTYPE_DOMAIN:
        case TYPTYPE_ENUM:
        case TYPTYPE_RANGE:
            return TYPEFUNC_SCALAR;
        case TYPTYPE_PSEUDO:
            if (typid == RECORDOID)
                return TYPEFUNC_RECORD;

            /*
             * We treat VOID and CSTRING as legitimate scalar datatypes,
             * mostly for the convenience of the JDBC driver (which wants to
             * be able to do "SELECT * FROM foo()" for all legitimately
             * user-callable functions).
             */
            if (typid == VOIDOID || typid == CSTRINGOID)
                return TYPEFUNC_SCALAR;
            return TYPEFUNC_OTHER;
    }
    /* shouldn't get here, probably */
    return TYPEFUNC_OTHER;
}


/*
 * get_func_arg_info
 *
 * Fetch info about the argument types, names, and IN/OUT modes from the
 * pg_proc tuple.  Return value is the total number of arguments.
 * Other results are palloc'd.  *p_argtypes is always filled in, but
 * *p_argnames and *p_argmodes will be set NULL in the default cases
 * (no names, and all IN arguments, respectively).
 *
 * Note that this function simply fetches what is in the pg_proc tuple;
 * it doesn't do any interpretation of polymorphic types.
 */
int
get_func_arg_info(HeapTuple procTup,
                  Oid **p_argtypes, char ***p_argnames, char **p_argmodes)
{
    Form_pg_proc procStruct = (Form_pg_proc) GETSTRUCT(procTup);
    Datum       proallargtypes;
    Datum       proargmodes;
    Datum       proargnames;
    bool        isNull;
    ArrayType  *arr;
    int         numargs;
    Datum      *elems;
    int         nelems;
    int         i;

    /* First discover the total number of parameters and get their types */
    proallargtypes = SysCacheGetAttr(PROCOID, procTup,
                                     Anum_pg_proc_proallargtypes,
                                     &isNull);
    if (!isNull)
    {
        /*
         * We expect the arrays to be 1-D arrays of the right types; verify
         * that.  For the OID and char arrays, we don't need to use
         * deconstruct_array() since the array data is just going to look like
         * a C array of values.
         */
        arr = DatumGetArrayTypeP(proallargtypes);       /* ensure not toasted */
        numargs = ARR_DIMS(arr)[0];
        if (ARR_NDIM(arr) != 1 ||
            numargs < 0 ||
            ARR_HASNULL(arr) ||
            ARR_ELEMTYPE(arr) != OIDOID)
            elog(ERROR, "proallargtypes is not a 1-D Oid array");
        Assert(numargs >= procStruct->pronargs);
        *p_argtypes = (Oid *) palloc(numargs * sizeof(Oid));
        memcpy(*p_argtypes, ARR_DATA_PTR(arr),
               numargs * sizeof(Oid));
    }
    else
    {
        /* If no proallargtypes, use proargtypes */
        numargs = procStruct->proargtypes.dim1;
        Assert(numargs == procStruct->pronargs);
        *p_argtypes = (Oid *) palloc(numargs * sizeof(Oid));
        memcpy(*p_argtypes, procStruct->proargtypes.values,
               numargs * sizeof(Oid));
    }

    /* Get argument names, if available */
    proargnames = SysCacheGetAttr(PROCOID, procTup,
                                  Anum_pg_proc_proargnames,
                                  &isNull);
    if (isNull)
        *p_argnames = NULL;
    else
    {
        deconstruct_array(DatumGetArrayTypeP(proargnames),
                          TEXTOID, -1, false, 'i',
                          &elems, NULL, &nelems);
        if (nelems != numargs)  /* should not happen */
            elog(ERROR, "proargnames must have the same number of elements as the function has arguments");
        *p_argnames = (char **) palloc(sizeof(char *) * numargs);
        for (i = 0; i < numargs; i++)
            (*p_argnames)[i] = TextDatumGetCString(elems[i]);
    }

    /* Get argument modes, if available */
    proargmodes = SysCacheGetAttr(PROCOID, procTup,
                                  Anum_pg_proc_proargmodes,
                                  &isNull);
    if (isNull)
        *p_argmodes = NULL;
    else
    {
        arr = DatumGetArrayTypeP(proargmodes);  /* ensure not toasted */
        if (ARR_NDIM(arr) != 1 ||
            ARR_DIMS(arr)[0] != numargs ||
            ARR_HASNULL(arr) ||
            ARR_ELEMTYPE(arr) != CHAROID)
            elog(ERROR, "proargmodes is not a 1-D char array");
        *p_argmodes = (char *) palloc(numargs * sizeof(char));
        memcpy(*p_argmodes, ARR_DATA_PTR(arr),
               numargs * sizeof(char));
    }

    return numargs;
}


/*
 * get_func_input_arg_names
 *
 * Extract the names of input arguments only, given a function's
 * proargnames and proargmodes entries in Datum form.
 *
 * Returns the number of input arguments, which is the length of the
 * palloc'd array returned to *arg_names.  Entries for unnamed args
 * are set to NULL.  You don't get anything if proargnames is NULL.
 */
int
get_func_input_arg_names(Datum proargnames, Datum proargmodes,
                         char ***arg_names)
{
    ArrayType  *arr;
    int         numargs;
    Datum      *argnames;
    char       *argmodes;
    char      **inargnames;
    int         numinargs;
    int         i;

    /* Do nothing if null proargnames */
    if (proargnames == PointerGetDatum(NULL))
    {
        *arg_names = NULL;
        return 0;
    }

    /*
     * We expect the arrays to be 1-D arrays of the right types; verify that.
     * For proargmodes, we don't need to use deconstruct_array() since the
     * array data is just going to look like a C array of values.
     */
    arr = DatumGetArrayTypeP(proargnames);      /* ensure not toasted */
    if (ARR_NDIM(arr) != 1 ||
        ARR_HASNULL(arr) ||
        ARR_ELEMTYPE(arr) != TEXTOID)
        elog(ERROR, "proargnames is not a 1-D text array");
    deconstruct_array(arr, TEXTOID, -1, false, 'i',
                      &argnames, NULL, &numargs);
    if (proargmodes != PointerGetDatum(NULL))
    {
        arr = DatumGetArrayTypeP(proargmodes);  /* ensure not toasted */
        if (ARR_NDIM(arr) != 1 ||
            ARR_DIMS(arr)[0] != numargs ||
            ARR_HASNULL(arr) ||
            ARR_ELEMTYPE(arr) != CHAROID)
            elog(ERROR, "proargmodes is not a 1-D char array");
        argmodes = (char *) ARR_DATA_PTR(arr);
    }
    else
        argmodes = NULL;

    /* zero elements probably shouldn't happen, but handle it gracefully */
    if (numargs <= 0)
    {
        *arg_names = NULL;
        return 0;
    }

    /* extract input-argument names */
    inargnames = (char **) palloc(numargs * sizeof(char *));
    numinargs = 0;
    for (i = 0; i < numargs; i++)
    {
        if (argmodes == NULL ||
            argmodes[i] == PROARGMODE_IN ||
            argmodes[i] == PROARGMODE_INOUT ||
            argmodes[i] == PROARGMODE_VARIADIC)
        {
            char       *pname = TextDatumGetCString(argnames[i]);

            if (pname[0] != '\0')
                inargnames[numinargs] = pname;
            else
                inargnames[numinargs] = NULL;
            numinargs++;
        }
    }

    *arg_names = inargnames;
    return numinargs;
}


/*
 * get_func_result_name
 *
 * If the function has exactly one output parameter, and that parameter
 * is named, return the name (as a palloc'd string).  Else return NULL.
 *
 * This is used to determine the default output column name for functions
 * returning scalar types.
 */
char *
get_func_result_name(Oid functionId)
{
    char       *result;
    HeapTuple   procTuple;
    Datum       proargmodes;
    Datum       proargnames;
    bool        isnull;
    ArrayType  *arr;
    int         numargs;
    char       *argmodes;
    Datum      *argnames;
    int         numoutargs;
    int         nargnames;
    int         i;

    /* First fetch the function's pg_proc row */
    procTuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(functionId));
    if (!HeapTupleIsValid(procTuple))
        elog(ERROR, "cache lookup failed for function %u", functionId);

    /* If there are no named OUT parameters, return NULL */
    if (heap_attisnull(procTuple, Anum_pg_proc_proargmodes) ||
        heap_attisnull(procTuple, Anum_pg_proc_proargnames))
        result = NULL;
    else
    {
        /* Get the data out of the tuple */
        proargmodes = SysCacheGetAttr(PROCOID, procTuple,
                                      Anum_pg_proc_proargmodes,
                                      &isnull);
        Assert(!isnull);
        proargnames = SysCacheGetAttr(PROCOID, procTuple,
                                      Anum_pg_proc_proargnames,
                                      &isnull);
        Assert(!isnull);

        /*
         * We expect the arrays to be 1-D arrays of the right types; verify
         * that.  For the char array, we don't need to use deconstruct_array()
         * since the array data is just going to look like a C array of
         * values.
         */
        arr = DatumGetArrayTypeP(proargmodes);  /* ensure not toasted */
        numargs = ARR_DIMS(arr)[0];
        if (ARR_NDIM(arr) != 1 ||
            numargs < 0 ||
            ARR_HASNULL(arr) ||
            ARR_ELEMTYPE(arr) != CHAROID)
            elog(ERROR, "proargmodes is not a 1-D char array");
        argmodes = (char *) ARR_DATA_PTR(arr);
        arr = DatumGetArrayTypeP(proargnames);  /* ensure not toasted */
        if (ARR_NDIM(arr) != 1 ||
            ARR_DIMS(arr)[0] != numargs ||
            ARR_HASNULL(arr) ||
            ARR_ELEMTYPE(arr) != TEXTOID)
            elog(ERROR, "proargnames is not a 1-D text array");
        deconstruct_array(arr, TEXTOID, -1, false, 'i',
                          &argnames, NULL, &nargnames);
        Assert(nargnames == numargs);

        /* scan for output argument(s) */
        result = NULL;
        numoutargs = 0;
        for (i = 0; i < numargs; i++)
        {
            if (argmodes[i] == PROARGMODE_IN ||
                argmodes[i] == PROARGMODE_VARIADIC)
                continue;
            Assert(argmodes[i] == PROARGMODE_OUT ||
                   argmodes[i] == PROARGMODE_INOUT ||
                   argmodes[i] == PROARGMODE_TABLE);
            if (++numoutargs > 1)
            {
                /* multiple out args, so forget it */
                result = NULL;
                break;
            }
            result = TextDatumGetCString(argnames[i]);
            if (result == NULL || result[0] == '\0')
            {
                /* Parameter is not named, so forget it */
                result = NULL;
                break;
            }
        }
    }

    ReleaseSysCache(procTuple);

    return result;
}


/*
 * build_function_result_tupdesc_t
 *
 * Given a pg_proc row for a function, return a tuple descriptor for the
 * result rowtype, or NULL if the function does not have OUT parameters.
 *
 * Note that this does not handle resolution of polymorphic types;
 * that is deliberate.
 */
TupleDesc
build_function_result_tupdesc_t(HeapTuple procTuple)
{
    Form_pg_proc procform = (Form_pg_proc) GETSTRUCT(procTuple);
    Datum       proallargtypes;
    Datum       proargmodes;
    Datum       proargnames;
    bool        isnull;

    /* Return NULL if the function isn't declared to return RECORD */
    if (procform->prorettype != RECORDOID)
        return NULL;

    /* If there are no OUT parameters, return NULL */
    if (heap_attisnull(procTuple, Anum_pg_proc_proallargtypes) ||
        heap_attisnull(procTuple, Anum_pg_proc_proargmodes))
        return NULL;

    /* Get the data out of the tuple */
    proallargtypes = SysCacheGetAttr(PROCOID, procTuple,
                                     Anum_pg_proc_proallargtypes,
                                     &isnull);
    Assert(!isnull);
    proargmodes = SysCacheGetAttr(PROCOID, procTuple,
                                  Anum_pg_proc_proargmodes,
                                  &isnull);
    Assert(!isnull);
    proargnames = SysCacheGetAttr(PROCOID, procTuple,
                                  Anum_pg_proc_proargnames,
                                  &isnull);
    if (isnull)
        proargnames = PointerGetDatum(NULL);    /* just to be sure */

    return build_function_result_tupdesc_d(proallargtypes,
                                           proargmodes,
                                           proargnames);
}

/*
 * build_function_result_tupdesc_d
 *
 * Build a RECORD function's tupledesc from the pg_proc proallargtypes,
 * proargmodes, and proargnames arrays.  This is split out for the
 * convenience of ProcedureCreate, which needs to be able to compute the
 * tupledesc before actually creating the function.
 *
 * Returns NULL if there are not at least two OUT or INOUT arguments.
 */
TupleDesc
build_function_result_tupdesc_d(Datum proallargtypes,
                                Datum proargmodes,
                                Datum proargnames)
{
    TupleDesc   desc;
    ArrayType  *arr;
    int         numargs;
    Oid        *argtypes;
    char       *argmodes;
    Datum      *argnames = NULL;
    Oid        *outargtypes;
    char      **outargnames;
    int         numoutargs;
    int         nargnames;
    int         i;

    /* Can't have output args if columns are null */
    if (proallargtypes == PointerGetDatum(NULL) ||
        proargmodes == PointerGetDatum(NULL))
        return NULL;

    /*
     * We expect the arrays to be 1-D arrays of the right types; verify that.
     * For the OID and char arrays, we don't need to use deconstruct_array()
     * since the array data is just going to look like a C array of values.
     */
    arr = DatumGetArrayTypeP(proallargtypes);   /* ensure not toasted */
    numargs = ARR_DIMS(arr)[0];
    if (ARR_NDIM(arr) != 1 ||
        numargs < 0 ||
        ARR_HASNULL(arr) ||
        ARR_ELEMTYPE(arr) != OIDOID)
        elog(ERROR, "proallargtypes is not a 1-D Oid array");
    argtypes = (Oid *) ARR_DATA_PTR(arr);
    arr = DatumGetArrayTypeP(proargmodes);      /* ensure not toasted */
    if (ARR_NDIM(arr) != 1 ||
        ARR_DIMS(arr)[0] != numargs ||
        ARR_HASNULL(arr) ||
        ARR_ELEMTYPE(arr) != CHAROID)
        elog(ERROR, "proargmodes is not a 1-D char array");
    argmodes = (char *) ARR_DATA_PTR(arr);
    if (proargnames != PointerGetDatum(NULL))
    {
        arr = DatumGetArrayTypeP(proargnames);  /* ensure not toasted */
        if (ARR_NDIM(arr) != 1 ||
            ARR_DIMS(arr)[0] != numargs ||
            ARR_HASNULL(arr) ||
            ARR_ELEMTYPE(arr) != TEXTOID)
            elog(ERROR, "proargnames is not a 1-D text array");
        deconstruct_array(arr, TEXTOID, -1, false, 'i',
                          &argnames, NULL, &nargnames);
        Assert(nargnames == numargs);
    }

    /* zero elements probably shouldn't happen, but handle it gracefully */
    if (numargs <= 0)
        return NULL;

    /* extract output-argument types and names */
    outargtypes = (Oid *) palloc(numargs * sizeof(Oid));
    outargnames = (char **) palloc(numargs * sizeof(char *));
    numoutargs = 0;
    for (i = 0; i < numargs; i++)
    {
        char       *pname;

        if (argmodes[i] == PROARGMODE_IN ||
            argmodes[i] == PROARGMODE_VARIADIC)
            continue;
        Assert(argmodes[i] == PROARGMODE_OUT ||
               argmodes[i] == PROARGMODE_INOUT ||
               argmodes[i] == PROARGMODE_TABLE);
        outargtypes[numoutargs] = argtypes[i];
        if (argnames)
            pname = TextDatumGetCString(argnames[i]);
        else
            pname = NULL;
        if (pname == NULL || pname[0] == '\0')
        {
            /* Parameter is not named, so gin up a column name */
            pname = (char *) palloc(32);
            snprintf(pname, 32, "column%d", numoutargs + 1);
        }
        outargnames[numoutargs] = pname;
        numoutargs++;
    }

    /*
     * If there is no output argument, or only one, the function does not
     * return tuples.
     */
    if (numoutargs < 2)
        return NULL;

    desc = CreateTemplateTupleDesc(numoutargs, false);
    for (i = 0; i < numoutargs; i++)
    {
        TupleDescInitEntry(desc, i + 1,
                           outargnames[i],
                           outargtypes[i],
                           -1,
                           0);
    }

    return desc;
}


/*
 * RelationNameGetTupleDesc
 *
 * Given a (possibly qualified) relation name, build a TupleDesc.
 *
 * Note: while this works as advertised, it's seldom the best way to
 * build a tupdesc for a function's result type.  It's kept around
 * only for backwards compatibility with existing user-written code.
 */
TupleDesc
RelationNameGetTupleDesc(const char *relname)
{
    RangeVar   *relvar;
    Relation    rel;
    TupleDesc   tupdesc;
    List       *relname_list;

    /* Open relation and copy the tuple description */
    relname_list = stringToQualifiedNameList(relname);
    relvar = makeRangeVarFromNameList(relname_list);
    rel = relation_openrv(relvar, AccessShareLock);
    tupdesc = CreateTupleDescCopy(RelationGetDescr(rel));
    relation_close(rel, AccessShareLock);

    return tupdesc;
}

/*
 * TypeGetTupleDesc
 *
 * Given a type Oid, build a TupleDesc.  (In most cases you should be
 * using get_call_result_type or one of its siblings instead of this
 * routine, so that you can handle OUT parameters, RECORD result type,
 * and polymorphic results.)
 *
 * If the type is composite, *and* a colaliases List is provided, *and*
 * the List is of natts length, use the aliases instead of the relation
 * attnames.  (NB: this usage is deprecated since it may result in
 * creation of unnecessary transient record types.)
 *
 * If the type is a base type, a single item alias List is required.
 */
TupleDesc
TypeGetTupleDesc(Oid typeoid, List *colaliases)
{
    TypeFuncClass functypclass = get_type_func_class(typeoid);
    TupleDesc   tupdesc = NULL;

    /*
     * Build a suitable tupledesc representing the output rows
     */
    if (functypclass == TYPEFUNC_COMPOSITE)
    {
        /* Composite data type, e.g. a table's row type */
        tupdesc = lookup_rowtype_tupdesc_copy(typeoid, -1);

        if (colaliases != NIL)
        {
            int         natts = tupdesc->natts;
            int         varattno;

            /* does the list length match the number of attributes? */
            if (list_length(colaliases) != natts)
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("number of aliases does not match number of columns")));

            /* OK, use the aliases instead */
            for (varattno = 0; varattno < natts; varattno++)
            {
                char       *label = strVal(list_nth(colaliases, varattno));

                if (label != NULL)
                    namestrcpy(&(tupdesc->attrs[varattno]->attname), label);
            }

            /* The tuple type is now an anonymous record type */
            tupdesc->tdtypeid = RECORDOID;
            tupdesc->tdtypmod = -1;
        }
    }
    else if (functypclass == TYPEFUNC_SCALAR)
    {
        /* Base data type, i.e. scalar */
        char       *attname;

        /* the alias list is required for base types */
        if (colaliases == NIL)
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("no column alias was provided")));

        /* the alias list length must be 1 */
        if (list_length(colaliases) != 1)
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
              errmsg("number of aliases does not match number of columns")));

        /* OK, get the column alias */
        attname = strVal(linitial(colaliases));

        tupdesc = CreateTemplateTupleDesc(1, false);
        TupleDescInitEntry(tupdesc,
                           (AttrNumber) 1,
                           attname,
                           typeoid,
                           -1,
                           0);
    }
    else if (functypclass == TYPEFUNC_RECORD)
    {
        /* XXX can't support this because typmod wasn't passed in ... */
        ereport(ERROR,
                (errcode(ERRCODE_DATATYPE_MISMATCH),
                 errmsg("could not determine row description for function returning record")));
    }
    else
    {
        /* crummy error message, but parser should have caught this */
        elog(ERROR, "function in FROM has unsupported return type");
    }

    return tupdesc;
}