parse_coerce.c

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/*-------------------------------------------------------------------------
 *
 * parse_coerce.c
 *      handle type coercions/conversions for parser
 *
 * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/parser/parse_coerce.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/htup_details.h"
#include "catalog/pg_cast.h"
#include "catalog/pg_class.h"
#include "catalog/pg_inherits.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "parser/parse_coerce.h"
#include "parser/parse_relation.h"
#include "parser/parse_type.h"
#include "utils/builtins.h"
#include "utils/datum.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
#include "utils/typcache.h"


static Node *coerce_type_typmod(Node *node,
                   Oid targetTypeId, int32 targetTypMod,
                   CoercionContext ccontext, CoercionForm cformat,
                   int location,
                   bool hideInputCoercion);
static void hide_coercion_node(Node *node);
static Node *build_coercion_expression(Node *node,
                          CoercionPathType pathtype,
                          Oid funcId,
                          Oid targetTypeId, int32 targetTypMod,
                          CoercionContext ccontext, CoercionForm cformat,
                          int location);
static Node *coerce_record_to_complex(ParseState *pstate, Node *node,
                         Oid targetTypeId,
                         CoercionContext ccontext,
                         CoercionForm cformat,
                         int location);
static bool is_complex_array(Oid typid);
static bool typeIsOfTypedTable(Oid reltypeId, Oid reloftypeId);


/*
 * coerce_to_target_type()
 *      Convert an expression to a target type and typmod.
 *
 * This is the general-purpose entry point for arbitrary type coercion
 * operations.  Direct use of the component operations can_coerce_type,
 * coerce_type, and coerce_type_typmod should be restricted to special
 * cases (eg, when the conversion is expected to succeed).
 *
 * Returns the possibly-transformed expression tree, or NULL if the type
 * conversion is not possible.  (We do this, rather than ereport'ing directly,
 * so that callers can generate custom error messages indicating context.)
 *
 * pstate - parse state (can be NULL, see coerce_type)
 * expr - input expression tree (already transformed by transformExpr)
 * exprtype - result type of expr
 * targettype - desired result type
 * targettypmod - desired result typmod
 * ccontext, cformat - context indicators to control coercions
 * location - parse location of the coercion request, or -1 if unknown/implicit
 */
Node *
coerce_to_target_type(ParseState *pstate, Node *expr, Oid exprtype,
                      Oid targettype, int32 targettypmod,
                      CoercionContext ccontext,
                      CoercionForm cformat,
                      int location)
{
    Node       *result;
    Node       *origexpr;

    if (!can_coerce_type(1, &exprtype, &targettype, ccontext))
        return NULL;

    /*
     * If the input has a CollateExpr at the top, strip it off, perform the
     * coercion, and put a new one back on.  This is annoying since it
     * duplicates logic in coerce_type, but if we don't do this then it's too
     * hard to tell whether coerce_type actually changed anything, and we
     * *must* know that to avoid possibly calling hide_coercion_node on
     * something that wasn't generated by coerce_type.  Note that if there are
     * multiple stacked CollateExprs, we just discard all but the topmost.
     */
    origexpr = expr;
    while (expr && IsA(expr, CollateExpr))
        expr = (Node *) ((CollateExpr *) expr)->arg;

    result = coerce_type(pstate, expr, exprtype,
                         targettype, targettypmod,
                         ccontext, cformat, location);

    /*
     * If the target is a fixed-length type, it may need a length coercion as
     * well as a type coercion.  If we find ourselves adding both, force the
     * inner coercion node to implicit display form.
     */
    result = coerce_type_typmod(result,
                                targettype, targettypmod,
                                ccontext, cformat, location,
                                (result != expr && !IsA(result, Const)));

    if (expr != origexpr)
    {
        /* Reinstall top CollateExpr */
        CollateExpr *coll = (CollateExpr *) origexpr;
        CollateExpr *newcoll = makeNode(CollateExpr);

        newcoll->arg = (Expr *) result;
        newcoll->collOid = coll->collOid;
        newcoll->location = coll->location;
        result = (Node *) newcoll;
    }

    return result;
}


/*
 * coerce_type()
 *      Convert an expression to a different type.
 *
 * The caller should already have determined that the coercion is possible;
 * see can_coerce_type.
 *
 * Normally, no coercion to a typmod (length) is performed here.  The caller
 * must call coerce_type_typmod as well, if a typmod constraint is wanted.
 * (But if the target type is a domain, it may internally contain a
 * typmod constraint, which will be applied inside coerce_to_domain.)
 * In some cases pg_cast specifies a type coercion function that also
 * applies length conversion, and in those cases only, the result will
 * already be properly coerced to the specified typmod.
 *
 * pstate is only used in the case that we are able to resolve the type of
 * a previously UNKNOWN Param.  It is okay to pass pstate = NULL if the
 * caller does not want type information updated for Params.
 *
 * Note: this function must not modify the given expression tree, only add
 * decoration on top of it.  See transformSetOperationTree, for example.
 */
Node *
coerce_type(ParseState *pstate, Node *node,
            Oid inputTypeId, Oid targetTypeId, int32 targetTypeMod,
            CoercionContext ccontext, CoercionForm cformat, int location)
{
    Node       *result;
    CoercionPathType pathtype;
    Oid         funcId;

    if (targetTypeId == inputTypeId ||
        node == NULL)
    {
        /* no conversion needed */
        return node;
    }
    if (targetTypeId == ANYOID ||
        targetTypeId == ANYELEMENTOID ||
        targetTypeId == ANYNONARRAYOID)
    {
        /*
         * Assume can_coerce_type verified that implicit coercion is okay.
         *
         * Note: by returning the unmodified node here, we are saying that
         * it's OK to treat an UNKNOWN constant as a valid input for a
         * function accepting ANY, ANYELEMENT, or ANYNONARRAY.  This should be
         * all right, since an UNKNOWN value is still a perfectly valid Datum.
         *
         * NB: we do NOT want a RelabelType here: the exposed type of the
         * function argument must be its actual type, not the polymorphic
         * pseudotype.
         */
        return node;
    }
    if (targetTypeId == ANYARRAYOID ||
        targetTypeId == ANYENUMOID ||
        targetTypeId == ANYRANGEOID)
    {
        /*
         * Assume can_coerce_type verified that implicit coercion is okay.
         *
         * These cases are unlike the ones above because the exposed type of
         * the argument must be an actual array, enum, or range type.  In
         * particular the argument must *not* be an UNKNOWN constant.  If it
         * is, we just fall through; below, we'll call anyarray_in,
         * anyenum_in, or anyrange_in, which will produce an error.  Also, if
         * what we have is a domain over array, enum, or range, we have to
         * relabel it to its base type.
         *
         * Note: currently, we can't actually see a domain-over-enum here,
         * since the other functions in this file will not match such a
         * parameter to ANYENUM.  But that should get changed eventually.
         */
        if (inputTypeId != UNKNOWNOID)
        {
            Oid         baseTypeId = getBaseType(inputTypeId);

            if (baseTypeId != inputTypeId)
            {
                RelabelType *r = makeRelabelType((Expr *) node,
                                                 baseTypeId, -1,
                                                 InvalidOid,
                                                 cformat);

                r->location = location;
                return (Node *) r;
            }
            /* Not a domain type, so return it as-is */
            return node;
        }
    }
    if (inputTypeId == UNKNOWNOID && IsA(node, Const))
    {
        /*
         * Input is a string constant with previously undetermined type. Apply
         * the target type's typinput function to it to produce a constant of
         * the target type.
         *
         * NOTE: this case cannot be folded together with the other
         * constant-input case, since the typinput function does not
         * necessarily behave the same as a type conversion function. For
         * example, int4's typinput function will reject "1.2", whereas
         * float-to-int type conversion will round to integer.
         *
         * XXX if the typinput function is not immutable, we really ought to
         * postpone evaluation of the function call until runtime. But there
         * is no way to represent a typinput function call as an expression
         * tree, because C-string values are not Datums. (XXX This *is*
         * possible as of 7.3, do we want to do it?)
         */
        Const      *con = (Const *) node;
        Const      *newcon = makeNode(Const);
        Oid         baseTypeId;
        int32       baseTypeMod;
        int32       inputTypeMod;
        Type        baseType;
        ParseCallbackState pcbstate;

        /*
         * If the target type is a domain, we want to call its base type's
         * input routine, not domain_in().  This is to avoid premature failure
         * when the domain applies a typmod: existing input routines follow
         * implicit-coercion semantics for length checks, which is not always
         * what we want here.  The needed check will be applied properly
         * inside coerce_to_domain().
         */
        baseTypeMod = targetTypeMod;
        baseTypeId = getBaseTypeAndTypmod(targetTypeId, &baseTypeMod);

        /*
         * For most types we pass typmod -1 to the input routine, because
         * existing input routines follow implicit-coercion semantics for
         * length checks, which is not always what we want here.  Any length
         * constraint will be applied later by our caller.  An exception
         * however is the INTERVAL type, for which we *must* pass the typmod
         * or it won't be able to obey the bizarre SQL-spec input rules. (Ugly
         * as sin, but so is this part of the spec...)
         */
        if (baseTypeId == INTERVALOID)
            inputTypeMod = baseTypeMod;
        else
            inputTypeMod = -1;

        baseType = typeidType(baseTypeId);

        newcon->consttype = baseTypeId;
        newcon->consttypmod = inputTypeMod;
        newcon->constcollid = typeTypeCollation(baseType);
        newcon->constlen = typeLen(baseType);
        newcon->constbyval = typeByVal(baseType);
        newcon->constisnull = con->constisnull;

        /*
         * We use the original literal's location regardless of the position
         * of the coercion.  This is a change from pre-9.2 behavior, meant to
         * simplify life for pg_stat_statements.
         */
        newcon->location = con->location;

        /*
         * Set up to point at the constant's text if the input routine throws
         * an error.
         */
        setup_parser_errposition_callback(&pcbstate, pstate, con->location);

        /*
         * We assume here that UNKNOWN's internal representation is the same
         * as CSTRING.
         */
        if (!con->constisnull)
            newcon->constvalue = stringTypeDatum(baseType,
                                                 DatumGetCString(con->constvalue),
                                                 inputTypeMod);
        else
            newcon->constvalue = stringTypeDatum(baseType,
                                                 NULL,
                                                 inputTypeMod);

        /*
         * If it's a varlena value, force it to be in non-expanded
         * (non-toasted) format; this avoids any possible dependency on
         * external values and improves consistency of representation.
         */
        if (!con->constisnull && newcon->constlen == -1)
            newcon->constvalue =
                PointerGetDatum(PG_DETOAST_DATUM(newcon->constvalue));

#ifdef RANDOMIZE_ALLOCATED_MEMORY

        /*
         * For pass-by-reference data types, repeat the conversion to see if
         * the input function leaves any uninitialized bytes in the result. We
         * can only detect that reliably if RANDOMIZE_ALLOCATED_MEMORY is
         * enabled, so we don't bother testing otherwise.  The reason we don't
         * want any instability in the input function is that comparison of
         * Const nodes relies on bytewise comparison of the datums, so if the
         * input function leaves garbage then subexpressions that should be
         * identical may not get recognized as such.  See pgsql-hackers
         * discussion of 2008-04-04.
         */
        if (!con->constisnull && !newcon->constbyval)
        {
            Datum       val2;

            val2 = stringTypeDatum(baseType,
                                   DatumGetCString(con->constvalue),
                                   inputTypeMod);
            if (newcon->constlen == -1)
                val2 = PointerGetDatum(PG_DETOAST_DATUM(val2));
            if (!datumIsEqual(newcon->constvalue, val2, false, newcon->constlen))
                elog(WARNING, "type %s has unstable input conversion for \"%s\"",
                     typeTypeName(baseType), DatumGetCString(con->constvalue));
        }
#endif

        cancel_parser_errposition_callback(&pcbstate);

        result = (Node *) newcon;

        /* If target is a domain, apply constraints. */
        if (baseTypeId != targetTypeId)
            result = coerce_to_domain(result,
                                      baseTypeId, baseTypeMod,
                                      targetTypeId,
                                      ccontext, cformat, location,
                                      false);

        ReleaseSysCache(baseType);

        return result;
    }
    if (IsA(node, Param) &&
        pstate != NULL && pstate->p_coerce_param_hook != NULL)
    {
        /*
         * Allow the CoerceParamHook to decide what happens.  It can return a
         * transformed node (very possibly the same Param node), or return
         * NULL to indicate we should proceed with normal coercion.
         */
        result = pstate->p_coerce_param_hook(pstate,
                                             (Param *) node,
                                             targetTypeId,
                                             targetTypeMod,
                                             location);
        if (result)
            return result;
    }
    if (IsA(node, CollateExpr))
    {
        /*
         * If we have a COLLATE clause, we have to push the coercion
         * underneath the COLLATE.  This is really ugly, but there is little
         * choice because the above hacks on Consts and Params wouldn't happen
         * otherwise.  This kluge has consequences in coerce_to_target_type.
         */
        CollateExpr *coll = (CollateExpr *) node;
        CollateExpr *newcoll = makeNode(CollateExpr);

        newcoll->arg = (Expr *)
            coerce_type(pstate, (Node *) coll->arg,
                        inputTypeId, targetTypeId, targetTypeMod,
                        ccontext, cformat, location);
        newcoll->collOid = coll->collOid;
        newcoll->location = coll->location;
        return (Node *) newcoll;
    }
    pathtype = find_coercion_pathway(targetTypeId, inputTypeId, ccontext,
                                     &funcId);
    if (pathtype != COERCION_PATH_NONE)
    {
        if (pathtype != COERCION_PATH_RELABELTYPE)
        {
            /*
             * Generate an expression tree representing run-time application
             * of the conversion function.  If we are dealing with a domain
             * target type, the conversion function will yield the base type,
             * and we need to extract the correct typmod to use from the
             * domain's typtypmod.
             */
            Oid         baseTypeId;
            int32       baseTypeMod;

            baseTypeMod = targetTypeMod;
            baseTypeId = getBaseTypeAndTypmod(targetTypeId, &baseTypeMod);

            result = build_coercion_expression(node, pathtype, funcId,
                                               baseTypeId, baseTypeMod,
                                               ccontext, cformat, location);

            /*
             * If domain, coerce to the domain type and relabel with domain
             * type ID, hiding the previous coercion node.
             */
            if (targetTypeId != baseTypeId)
                result = coerce_to_domain(result, baseTypeId, baseTypeMod,
                                          targetTypeId,
                                          ccontext, cformat, location,
                                          true);
        }
        else
        {
            /*
             * We don't need to do a physical conversion, but we do need to
             * attach a RelabelType node so that the expression will be seen
             * to have the intended type when inspected by higher-level code.
             *
             * Also, domains may have value restrictions beyond the base type
             * that must be accounted for.  If the destination is a domain
             * then we won't need a RelabelType node.
             */
            result = coerce_to_domain(node, InvalidOid, -1, targetTypeId,
                                      ccontext, cformat, location,
                                      false);
            if (result == node)
            {
                /*
                 * XXX could we label result with exprTypmod(node) instead of
                 * default -1 typmod, to save a possible length-coercion
                 * later? Would work if both types have same interpretation of
                 * typmod, which is likely but not certain.
                 */
                RelabelType *r = makeRelabelType((Expr *) result,
                                                 targetTypeId, -1,
                                                 InvalidOid,
                                                 cformat);

                r->location = location;
                result = (Node *) r;
            }
        }
        return result;
    }
    if (inputTypeId == RECORDOID &&
        ISCOMPLEX(targetTypeId))
    {
        /* Coerce a RECORD to a specific complex type */
        return coerce_record_to_complex(pstate, node, targetTypeId,
                                        ccontext, cformat, location);
    }
    if (targetTypeId == RECORDOID &&
        ISCOMPLEX(inputTypeId))
    {
        /* Coerce a specific complex type to RECORD */
        /* NB: we do NOT want a RelabelType here */
        return node;
    }
#ifdef NOT_USED
    if (inputTypeId == RECORDARRAYOID &&
        is_complex_array(targetTypeId))
    {
        /* Coerce record[] to a specific complex array type */
        /* not implemented yet ... */
    }
#endif
    if (targetTypeId == RECORDARRAYOID &&
        is_complex_array(inputTypeId))
    {
        /* Coerce a specific complex array type to record[] */
        /* NB: we do NOT want a RelabelType here */
        return node;
    }
    if (typeInheritsFrom(inputTypeId, targetTypeId)
        || typeIsOfTypedTable(inputTypeId, targetTypeId))
    {
        /*
         * Input class type is a subclass of target, so generate an
         * appropriate runtime conversion (removing unneeded columns and
         * possibly rearranging the ones that are wanted).
         *
         * We will also get here when the input is a domain over a subclass of
         * the target type.  To keep life simple for the executor, we define
         * ConvertRowtypeExpr as only working between regular composite types;
         * therefore, in such cases insert a RelabelType to smash the input
         * expression down to its base type.
         */
        Oid         baseTypeId = getBaseType(inputTypeId);
        ConvertRowtypeExpr *r = makeNode(ConvertRowtypeExpr);

        if (baseTypeId != inputTypeId)
        {
            RelabelType *rt = makeRelabelType((Expr *) node,
                                              baseTypeId, -1,
                                              InvalidOid,
                                              COERCE_IMPLICIT_CAST);

            rt->location = location;
            node = (Node *) rt;
        }
        r->arg = (Expr *) node;
        r->resulttype = targetTypeId;
        r->convertformat = cformat;
        r->location = location;
        return (Node *) r;
    }
    /* If we get here, caller blew it */
    elog(ERROR, "failed to find conversion function from %s to %s",
         format_type_be(inputTypeId), format_type_be(targetTypeId));
    return NULL;                /* keep compiler quiet */
}


/*
 * can_coerce_type()
 *      Can input_typeids be coerced to target_typeids?
 *
 * We must be told the context (CAST construct, assignment, implicit coercion)
 * as this determines the set of available casts.
 */
bool
can_coerce_type(int nargs, Oid *input_typeids, Oid *target_typeids,
                CoercionContext ccontext)
{
    bool        have_generics = false;
    int         i;

    /* run through argument list... */
    for (i = 0; i < nargs; i++)
    {
        Oid         inputTypeId = input_typeids[i];
        Oid         targetTypeId = target_typeids[i];
        CoercionPathType pathtype;
        Oid         funcId;

        /* no problem if same type */
        if (inputTypeId == targetTypeId)
            continue;

        /* accept if target is ANY */
        if (targetTypeId == ANYOID)
            continue;

        /* accept if target is polymorphic, for now */
        if (IsPolymorphicType(targetTypeId))
        {
            have_generics = true;   /* do more checking later */
            continue;
        }

        /*
         * If input is an untyped string constant, assume we can convert it to
         * anything.
         */
        if (inputTypeId == UNKNOWNOID)
            continue;

        /*
         * If pg_cast shows that we can coerce, accept.  This test now covers
         * both binary-compatible and coercion-function cases.
         */
        pathtype = find_coercion_pathway(targetTypeId, inputTypeId, ccontext,
                                         &funcId);
        if (pathtype != COERCION_PATH_NONE)
            continue;

        /*
         * If input is RECORD and target is a composite type, assume we can
         * coerce (may need tighter checking here)
         */
        if (inputTypeId == RECORDOID &&
            ISCOMPLEX(targetTypeId))
            continue;

        /*
         * If input is a composite type and target is RECORD, accept
         */
        if (targetTypeId == RECORDOID &&
            ISCOMPLEX(inputTypeId))
            continue;

#ifdef NOT_USED                 /* not implemented yet */

        /*
         * If input is record[] and target is a composite array type, assume
         * we can coerce (may need tighter checking here)
         */
        if (inputTypeId == RECORDARRAYOID &&
            is_complex_array(targetTypeId))
            continue;
#endif

        /*
         * If input is a composite array type and target is record[], accept
         */
        if (targetTypeId == RECORDARRAYOID &&
            is_complex_array(inputTypeId))
            continue;

        /*
         * If input is a class type that inherits from target, accept
         */
        if (typeInheritsFrom(inputTypeId, targetTypeId)
            || typeIsOfTypedTable(inputTypeId, targetTypeId))
            continue;

        /*
         * Else, cannot coerce at this argument position
         */
        return false;
    }

    /* If we found any generic argument types, cross-check them */
    if (have_generics)
    {
        if (!check_generic_type_consistency(input_typeids, target_typeids,
                                            nargs))
            return false;
    }

    return true;
}


/*
 * Create an expression tree to represent coercion to a domain type.
 *
 * 'arg': input expression
 * 'baseTypeId': base type of domain, if known (pass InvalidOid if caller
 *      has not bothered to look this up)
 * 'baseTypeMod': base type typmod of domain, if known (pass -1 if caller
 *      has not bothered to look this up)
 * 'typeId': target type to coerce to
 * 'ccontext': context indicator to control coercions
 * 'cformat': coercion display format
 * 'location': coercion request location
 * 'hideInputCoercion': if true, hide the input coercion under this one.
 *
 * If the target type isn't a domain, the given 'arg' is returned as-is.
 */
Node *
coerce_to_domain(Node *arg, Oid baseTypeId, int32 baseTypeMod, Oid typeId,
                 CoercionContext ccontext, CoercionForm cformat, int location,
                 bool hideInputCoercion)
{
    CoerceToDomain *result;

    /* Get the base type if it hasn't been supplied */
    if (baseTypeId == InvalidOid)
        baseTypeId = getBaseTypeAndTypmod(typeId, &baseTypeMod);

    /* If it isn't a domain, return the node as it was passed in */
    if (baseTypeId == typeId)
        return arg;

    /* Suppress display of nested coercion steps */
    if (hideInputCoercion)
        hide_coercion_node(arg);

    /*
     * If the domain applies a typmod to its base type, build the appropriate
     * coercion step.  Mark it implicit for display purposes, because we don't
     * want it shown separately by ruleutils.c; but the isExplicit flag passed
     * to the conversion function depends on the manner in which the domain
     * coercion is invoked, so that the semantics of implicit and explicit
     * coercion differ.  (Is that really the behavior we want?)
     *
     * NOTE: because we apply this as part of the fixed expression structure,
     * ALTER DOMAIN cannot alter the typtypmod.  But it's unclear that that
     * would be safe to do anyway, without lots of knowledge about what the
     * base type thinks the typmod means.
     */
    arg = coerce_type_typmod(arg, baseTypeId, baseTypeMod,
                             ccontext, COERCE_IMPLICIT_CAST, location,
                             false);

    /*
     * Now build the domain coercion node.  This represents run-time checking
     * of any constraints currently attached to the domain.  This also ensures
     * that the expression is properly labeled as to result type.
     */
    result = makeNode(CoerceToDomain);
    result->arg = (Expr *) arg;
    result->resulttype = typeId;
    result->resulttypmod = -1;  /* currently, always -1 for domains */
    /* resultcollid will be set by parse_collate.c */
    result->coercionformat = cformat;
    result->location = location;

    return (Node *) result;
}


/*
 * coerce_type_typmod()
 *      Force a value to a particular typmod, if meaningful and possible.
 *
 * This is applied to values that are going to be stored in a relation
 * (where we have an atttypmod for the column) as well as values being
 * explicitly CASTed (where the typmod comes from the target type spec).
 *
 * The caller must have already ensured that the value is of the correct
 * type, typically by applying coerce_type.
 *
 * ccontext may affect semantics, depending on whether the length coercion
 * function pays attention to the isExplicit flag it's passed.
 *
 * cformat determines the display properties of the generated node (if any).
 *
 * If hideInputCoercion is true *and* we generate a node, the input node is
 * forced to IMPLICIT display form, so that only the typmod coercion node will
 * be visible when displaying the expression.
 *
 * NOTE: this does not need to work on domain types, because any typmod
 * coercion for a domain is considered to be part of the type coercion
 * needed to produce the domain value in the first place.  So, no getBaseType.
 */
static Node *
coerce_type_typmod(Node *node, Oid targetTypeId, int32 targetTypMod,
                   CoercionContext ccontext, CoercionForm cformat,
                   int location,
                   bool hideInputCoercion)
{
    CoercionPathType pathtype;
    Oid         funcId;

    /*
     * A negative typmod is assumed to mean that no coercion is wanted. Also,
     * skip coercion if already done.
     */
    if (targetTypMod < 0 || targetTypMod == exprTypmod(node))
        return node;

    pathtype = find_typmod_coercion_function(targetTypeId, &funcId);

    if (pathtype != COERCION_PATH_NONE)
    {
        /* Suppress display of nested coercion steps */
        if (hideInputCoercion)
            hide_coercion_node(node);

        node = build_coercion_expression(node, pathtype, funcId,
                                         targetTypeId, targetTypMod,
                                         ccontext, cformat, location);
    }

    return node;
}

/*
 * Mark a coercion node as IMPLICIT so it will never be displayed by
 * ruleutils.c.  We use this when we generate a nest of coercion nodes
 * to implement what is logically one conversion; the inner nodes are
 * forced to IMPLICIT_CAST format.  This does not change their semantics,
 * only display behavior.
 *
 * It is caller error to call this on something that doesn't have a
 * CoercionForm field.
 */
static void
hide_coercion_node(Node *node)
{
    if (IsA(node, FuncExpr))
        ((FuncExpr *) node)->funcformat = COERCE_IMPLICIT_CAST;
    else if (IsA(node, RelabelType))
        ((RelabelType *) node)->relabelformat = COERCE_IMPLICIT_CAST;
    else if (IsA(node, CoerceViaIO))
        ((CoerceViaIO *) node)->coerceformat = COERCE_IMPLICIT_CAST;
    else if (IsA(node, ArrayCoerceExpr))
        ((ArrayCoerceExpr *) node)->coerceformat = COERCE_IMPLICIT_CAST;
    else if (IsA(node, ConvertRowtypeExpr))
        ((ConvertRowtypeExpr *) node)->convertformat = COERCE_IMPLICIT_CAST;
    else if (IsA(node, RowExpr))
        ((RowExpr *) node)->row_format = COERCE_IMPLICIT_CAST;
    else if (IsA(node, CoerceToDomain))
        ((CoerceToDomain *) node)->coercionformat = COERCE_IMPLICIT_CAST;
    else
        elog(ERROR, "unsupported node type: %d", (int) nodeTag(node));
}

/*
 * build_coercion_expression()
 *      Construct an expression tree for applying a pg_cast entry.
 *
 * This is used for both type-coercion and length-coercion operations,
 * since there is no difference in terms of the calling convention.
 */
static Node *
build_coercion_expression(Node *node,
                          CoercionPathType pathtype,
                          Oid funcId,
                          Oid targetTypeId, int32 targetTypMod,
                          CoercionContext ccontext, CoercionForm cformat,
                          int location)
{
    int         nargs = 0;

    if (OidIsValid(funcId))
    {
        HeapTuple   tp;
        Form_pg_proc procstruct;

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

        /*
         * These Asserts essentially check that function is a legal coercion
         * function.  We can't make the seemingly obvious tests on prorettype
         * and proargtypes[0], even in the COERCION_PATH_FUNC case, because of
         * various binary-compatibility cases.
         */
        /* Assert(targetTypeId == procstruct->prorettype); */
        Assert(!procstruct->proretset);
        Assert(procstruct->prokind == PROKIND_FUNCTION);
        nargs = procstruct->pronargs;
        Assert(nargs >= 1 && nargs <= 3);
        /* Assert(procstruct->proargtypes.values[0] == exprType(node)); */
        Assert(nargs < 2 || procstruct->proargtypes.values[1] == INT4OID);
        Assert(nargs < 3 || procstruct->proargtypes.values[2] == BOOLOID);

        ReleaseSysCache(tp);
    }

    if (pathtype == COERCION_PATH_FUNC)
    {
        /* We build an ordinary FuncExpr with special arguments */
        FuncExpr   *fexpr;
        List       *args;
        Const      *cons;

        Assert(OidIsValid(funcId));

        args = list_make1(node);

        if (nargs >= 2)
        {
            /* Pass target typmod as an int4 constant */
            cons = makeConst(INT4OID,
                             -1,
                             InvalidOid,
                             sizeof(int32),
                             Int32GetDatum(targetTypMod),
                             false,
                             true);

            args = lappend(args, cons);
        }

        if (nargs == 3)
        {
            /* Pass it a boolean isExplicit parameter, too */
            cons = makeConst(BOOLOID,
                             -1,
                             InvalidOid,
                             sizeof(bool),
                             BoolGetDatum(ccontext == COERCION_EXPLICIT),
                             false,
                             true);

            args = lappend(args, cons);
        }

        fexpr = makeFuncExpr(funcId, targetTypeId, args,
                             InvalidOid, InvalidOid, cformat);
        fexpr->location = location;
        return (Node *) fexpr;
    }
    else if (pathtype == COERCION_PATH_ARRAYCOERCE)
    {
        /* We need to build an ArrayCoerceExpr */
        ArrayCoerceExpr *acoerce = makeNode(ArrayCoerceExpr);
        CaseTestExpr *ctest = makeNode(CaseTestExpr);
        Oid         sourceBaseTypeId;
        int32       sourceBaseTypeMod;
        Oid         targetElementType;
        Node       *elemexpr;

        /*
         * Look through any domain over the source array type.  Note we don't
         * expect that the target type is a domain; it must be a plain array.
         * (To get to a domain target type, we'll do coerce_to_domain later.)
         */
        sourceBaseTypeMod = exprTypmod(node);
        sourceBaseTypeId = getBaseTypeAndTypmod(exprType(node),
                                                &sourceBaseTypeMod);

        /* Set up CaseTestExpr representing one element of source array */
        ctest->typeId = get_element_type(sourceBaseTypeId);
        Assert(OidIsValid(ctest->typeId));
        ctest->typeMod = sourceBaseTypeMod;
        ctest->collation = InvalidOid;  /* Assume coercions don't care */

        /* And coerce it to the target element type */
        targetElementType = get_element_type(targetTypeId);
        Assert(OidIsValid(targetElementType));

        elemexpr = coerce_to_target_type(NULL,
                                         (Node *) ctest,
                                         ctest->typeId,
                                         targetElementType,
                                         targetTypMod,
                                         ccontext,
                                         cformat,
                                         location);
        if (elemexpr == NULL)   /* shouldn't happen */
            elog(ERROR, "failed to coerce array element type as expected");

        acoerce->arg = (Expr *) node;
        acoerce->elemexpr = (Expr *) elemexpr;
        acoerce->resulttype = targetTypeId;

        /*
         * Label the output as having a particular element typmod only if we
         * ended up with a per-element expression that is labeled that way.
         */
        acoerce->resulttypmod = exprTypmod(elemexpr);
        /* resultcollid will be set by parse_collate.c */
        acoerce->coerceformat = cformat;
        acoerce->location = location;

        return (Node *) acoerce;
    }
    else if (pathtype == COERCION_PATH_COERCEVIAIO)
    {
        /* We need to build a CoerceViaIO node */
        CoerceViaIO *iocoerce = makeNode(CoerceViaIO);

        Assert(!OidIsValid(funcId));

        iocoerce->arg = (Expr *) node;
        iocoerce->resulttype = targetTypeId;
        /* resultcollid will be set by parse_collate.c */
        iocoerce->coerceformat = cformat;
        iocoerce->location = location;

        return (Node *) iocoerce;
    }
    else
    {
        elog(ERROR, "unsupported pathtype %d in build_coercion_expression",
             (int) pathtype);
        return NULL;            /* keep compiler quiet */
    }
}


/*
 * coerce_record_to_complex
 *      Coerce a RECORD to a specific composite type.
 *
 * Currently we only support this for inputs that are RowExprs or whole-row
 * Vars.
 */
static Node *
coerce_record_to_complex(ParseState *pstate, Node *node,
                         Oid targetTypeId,
                         CoercionContext ccontext,
                         CoercionForm cformat,
                         int location)
{
    RowExpr    *rowexpr;
    Oid         baseTypeId;
    int32       baseTypeMod = -1;
    TupleDesc   tupdesc;
    List       *args = NIL;
    List       *newargs;
    int         i;
    int         ucolno;
    ListCell   *arg;

    if (node && IsA(node, RowExpr))
    {
        /*
         * Since the RowExpr must be of type RECORD, we needn't worry about it
         * containing any dropped columns.
         */
        args = ((RowExpr *) node)->args;
    }
    else if (node && IsA(node, Var) &&
             ((Var *) node)->varattno == InvalidAttrNumber)
    {
        int         rtindex = ((Var *) node)->varno;
        int         sublevels_up = ((Var *) node)->varlevelsup;
        int         vlocation = ((Var *) node)->location;
        RangeTblEntry *rte;

        rte = GetRTEByRangeTablePosn(pstate, rtindex, sublevels_up);
        expandRTE(rte, rtindex, sublevels_up, vlocation, false,
                  NULL, &args);
    }
    else
        ereport(ERROR,
                (errcode(ERRCODE_CANNOT_COERCE),
                 errmsg("cannot cast type %s to %s",
                        format_type_be(RECORDOID),
                        format_type_be(targetTypeId)),
                 parser_coercion_errposition(pstate, location, node)));

    /*
     * Look up the composite type, accounting for possibility that what we are
     * given is a domain over composite.
     */
    baseTypeId = getBaseTypeAndTypmod(targetTypeId, &baseTypeMod);
    tupdesc = lookup_rowtype_tupdesc(baseTypeId, baseTypeMod);

    /* Process the fields */
    newargs = NIL;
    ucolno = 1;
    arg = list_head(args);
    for (i = 0; i < tupdesc->natts; i++)
    {
        Node       *expr;
        Node       *cexpr;
        Oid         exprtype;
        Form_pg_attribute attr = TupleDescAttr(tupdesc, i);

        /* Fill in NULLs for dropped columns in rowtype */
        if (attr->attisdropped)
        {
            /*
             * can't use atttypid here, but it doesn't really matter what type
             * the Const claims to be.
             */
            newargs = lappend(newargs,
                              makeNullConst(INT4OID, -1, InvalidOid));
            continue;
        }

        if (arg == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_CANNOT_COERCE),
                     errmsg("cannot cast type %s to %s",
                            format_type_be(RECORDOID),
                            format_type_be(targetTypeId)),
                     errdetail("Input has too few columns."),
                     parser_coercion_errposition(pstate, location, node)));
        expr = (Node *) lfirst(arg);
        exprtype = exprType(expr);

        cexpr = coerce_to_target_type(pstate,
                                      expr, exprtype,
                                      attr->atttypid,
                                      attr->atttypmod,
                                      ccontext,
                                      COERCE_IMPLICIT_CAST,
                                      -1);
        if (cexpr == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_CANNOT_COERCE),
                     errmsg("cannot cast type %s to %s",
                            format_type_be(RECORDOID),
                            format_type_be(targetTypeId)),
                     errdetail("Cannot cast type %s to %s in column %d.",
                               format_type_be(exprtype),
                               format_type_be(attr->atttypid),
                               ucolno),
                     parser_coercion_errposition(pstate, location, expr)));
        newargs = lappend(newargs, cexpr);
        ucolno++;
        arg = lnext(arg);
    }
    if (arg != NULL)
        ereport(ERROR,
                (errcode(ERRCODE_CANNOT_COERCE),
                 errmsg("cannot cast type %s to %s",
                        format_type_be(RECORDOID),
                        format_type_be(targetTypeId)),
                 errdetail("Input has too many columns."),
                 parser_coercion_errposition(pstate, location, node)));

    ReleaseTupleDesc(tupdesc);

    rowexpr = makeNode(RowExpr);
    rowexpr->args = newargs;
    rowexpr->row_typeid = baseTypeId;
    rowexpr->row_format = cformat;
    rowexpr->colnames = NIL;    /* not needed for named target type */
    rowexpr->location = location;

    /* If target is a domain, apply constraints */
    if (baseTypeId != targetTypeId)
    {
        rowexpr->row_format = COERCE_IMPLICIT_CAST;
        return coerce_to_domain((Node *) rowexpr,
                                baseTypeId, baseTypeMod,
                                targetTypeId,
                                ccontext, cformat, location,
                                false);
    }

    return (Node *) rowexpr;
}

/*
 * coerce_to_boolean()
 *      Coerce an argument of a construct that requires boolean input
 *      (AND, OR, NOT, etc).  Also check that input is not a set.
 *
 * Returns the possibly-transformed node tree.
 *
 * As with coerce_type, pstate may be NULL if no special unknown-Param
 * processing is wanted.
 */
Node *
coerce_to_boolean(ParseState *pstate, Node *node,
                  const char *constructName)
{
    Oid         inputTypeId = exprType(node);

    if (inputTypeId != BOOLOID)
    {
        Node       *newnode;

        newnode = coerce_to_target_type(pstate, node, inputTypeId,
                                        BOOLOID, -1,
                                        COERCION_ASSIGNMENT,
                                        COERCE_IMPLICIT_CAST,
                                        -1);
        if (newnode == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
            /* translator: first %s is name of a SQL construct, eg WHERE */
                     errmsg("argument of %s must be type %s, not type %s",
                            constructName, "boolean",
                            format_type_be(inputTypeId)),
                     parser_errposition(pstate, exprLocation(node))));
        node = newnode;
    }

    if (expression_returns_set(node))
        ereport(ERROR,
                (errcode(ERRCODE_DATATYPE_MISMATCH),
        /* translator: %s is name of a SQL construct, eg WHERE */
                 errmsg("argument of %s must not return a set",
                        constructName),
                 parser_errposition(pstate, exprLocation(node))));

    return node;
}

/*
 * coerce_to_specific_type_typmod()
 *      Coerce an argument of a construct that requires a specific data type,
 *      with a specific typmod.  Also check that input is not a set.
 *
 * Returns the possibly-transformed node tree.
 *
 * As with coerce_type, pstate may be NULL if no special unknown-Param
 * processing is wanted.
 */
Node *
coerce_to_specific_type_typmod(ParseState *pstate, Node *node,
                               Oid targetTypeId, int32 targetTypmod,
                               const char *constructName)
{
    Oid         inputTypeId = exprType(node);

    if (inputTypeId != targetTypeId)
    {
        Node       *newnode;

        newnode = coerce_to_target_type(pstate, node, inputTypeId,
                                        targetTypeId, targetTypmod,
                                        COERCION_ASSIGNMENT,
                                        COERCE_IMPLICIT_CAST,
                                        -1);
        if (newnode == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
            /* translator: first %s is name of a SQL construct, eg LIMIT */
                     errmsg("argument of %s must be type %s, not type %s",
                            constructName,
                            format_type_be(targetTypeId),
                            format_type_be(inputTypeId)),
                     parser_errposition(pstate, exprLocation(node))));
        node = newnode;
    }

    if (expression_returns_set(node))
        ereport(ERROR,
                (errcode(ERRCODE_DATATYPE_MISMATCH),
        /* translator: %s is name of a SQL construct, eg LIMIT */
                 errmsg("argument of %s must not return a set",
                        constructName),
                 parser_errposition(pstate, exprLocation(node))));

    return node;
}

/*
 * coerce_to_specific_type()
 *      Coerce an argument of a construct that requires a specific data type.
 *      Also check that input is not a set.
 *
 * Returns the possibly-transformed node tree.
 *
 * As with coerce_type, pstate may be NULL if no special unknown-Param
 * processing is wanted.
 */
Node *
coerce_to_specific_type(ParseState *pstate, Node *node,
                        Oid targetTypeId,
                        const char *constructName)
{
    return coerce_to_specific_type_typmod(pstate, node,
                                          targetTypeId, -1,
                                          constructName);
}

/*
 * parser_coercion_errposition - report coercion error location, if possible
 *
 * We prefer to point at the coercion request (CAST, ::, etc) if possible;
 * but there may be no such location in the case of an implicit coercion.
 * In that case point at the input expression.
 *
 * XXX possibly this is more generally useful than coercion errors;
 * if so, should rename and place with parser_errposition.
 */
int
parser_coercion_errposition(ParseState *pstate,
                            int coerce_location,
                            Node *input_expr)
{
    if (coerce_location >= 0)
        return parser_errposition(pstate, coerce_location);
    else
        return parser_errposition(pstate, exprLocation(input_expr));
}


/*
 * select_common_type()
 *      Determine the common supertype of a list of input expressions.
 *      This is used for determining the output type of CASE, UNION,
 *      and similar constructs.
 *
 * 'exprs' is a *nonempty* list of expressions.  Note that earlier items
 * in the list will be preferred if there is doubt.
 * 'context' is a phrase to use in the error message if we fail to select
 * a usable type.  Pass NULL to have the routine return InvalidOid
 * rather than throwing an error on failure.
 * 'which_expr': if not NULL, receives a pointer to the particular input
 * expression from which the result type was taken.
 */
Oid
select_common_type(ParseState *pstate, List *exprs, const char *context,
                   Node **which_expr)
{
    Node       *pexpr;
    Oid         ptype;
    TYPCATEGORY pcategory;
    bool        pispreferred;
    ListCell   *lc;

    Assert(exprs != NIL);
    pexpr = (Node *) linitial(exprs);
    lc = lnext(list_head(exprs));
    ptype = exprType(pexpr);

    /*
     * If all input types are valid and exactly the same, just pick that type.
     * This is the only way that we will resolve the result as being a domain
     * type; otherwise domains are smashed to their base types for comparison.
     */
    if (ptype != UNKNOWNOID)
    {
        for_each_cell(lc, lc)
        {
            Node       *nexpr = (Node *) lfirst(lc);
            Oid         ntype = exprType(nexpr);

            if (ntype != ptype)
                break;
        }
        if (lc == NULL)         /* got to the end of the list? */
        {
            if (which_expr)
                *which_expr = pexpr;
            return ptype;
        }
    }

    /*
     * Nope, so set up for the full algorithm.  Note that at this point, lc
     * points to the first list item with type different from pexpr's; we need
     * not re-examine any items the previous loop advanced over.
     */
    ptype = getBaseType(ptype);
    get_type_category_preferred(ptype, &pcategory, &pispreferred);

    for_each_cell(lc, lc)
    {
        Node       *nexpr = (Node *) lfirst(lc);
        Oid         ntype = getBaseType(exprType(nexpr));

        /* move on to next one if no new information... */
        if (ntype != UNKNOWNOID && ntype != ptype)
        {
            TYPCATEGORY ncategory;
            bool        nispreferred;

            get_type_category_preferred(ntype, &ncategory, &nispreferred);
            if (ptype == UNKNOWNOID)
            {
                /* so far, only unknowns so take anything... */
                pexpr = nexpr;
                ptype = ntype;
                pcategory = ncategory;
                pispreferred = nispreferred;
            }
            else if (ncategory != pcategory)
            {
                /*
                 * both types in different categories? then not much hope...
                 */
                if (context == NULL)
                    return InvalidOid;
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                /*------
                  translator: first %s is name of a SQL construct, eg CASE */
                         errmsg("%s types %s and %s cannot be matched",
                                context,
                                format_type_be(ptype),
                                format_type_be(ntype)),
                         parser_errposition(pstate, exprLocation(nexpr))));
            }
            else if (!pispreferred &&
                     can_coerce_type(1, &ptype, &ntype, COERCION_IMPLICIT) &&
                     !can_coerce_type(1, &ntype, &ptype, COERCION_IMPLICIT))
            {
                /*
                 * take new type if can coerce to it implicitly but not the
                 * other way; but if we have a preferred type, stay on it.
                 */
                pexpr = nexpr;
                ptype = ntype;
                pcategory = ncategory;
                pispreferred = nispreferred;
            }
        }
    }

    /*
     * If all the inputs were UNKNOWN type --- ie, unknown-type literals ---
     * then resolve as type TEXT.  This situation comes up with constructs
     * like SELECT (CASE WHEN foo THEN 'bar' ELSE 'baz' END); SELECT 'foo'
     * UNION SELECT 'bar'; It might seem desirable to leave the construct's
     * output type as UNKNOWN, but that really doesn't work, because we'd
     * probably end up needing a runtime coercion from UNKNOWN to something
     * else, and we usually won't have it.  We need to coerce the unknown
     * literals while they are still literals, so a decision has to be made
     * now.
     */
    if (ptype == UNKNOWNOID)
        ptype = TEXTOID;

    if (which_expr)
        *which_expr = pexpr;
    return ptype;
}

/*
 * coerce_to_common_type()
 *      Coerce an expression to the given type.
 *
 * This is used following select_common_type() to coerce the individual
 * expressions to the desired type.  'context' is a phrase to use in the
 * error message if we fail to coerce.
 *
 * As with coerce_type, pstate may be NULL if no special unknown-Param
 * processing is wanted.
 */
Node *
coerce_to_common_type(ParseState *pstate, Node *node,
                      Oid targetTypeId, const char *context)
{
    Oid         inputTypeId = exprType(node);

    if (inputTypeId == targetTypeId)
        return node;            /* no work */
    if (can_coerce_type(1, &inputTypeId, &targetTypeId, COERCION_IMPLICIT))
        node = coerce_type(pstate, node, inputTypeId, targetTypeId, -1,
                           COERCION_IMPLICIT, COERCE_IMPLICIT_CAST, -1);
    else
        ereport(ERROR,
                (errcode(ERRCODE_CANNOT_COERCE),
        /* translator: first %s is name of a SQL construct, eg CASE */
                 errmsg("%s could not convert type %s to %s",
                        context,
                        format_type_be(inputTypeId),
                        format_type_be(targetTypeId)),
                 parser_errposition(pstate, exprLocation(node))));
    return node;
}

/*
 * check_generic_type_consistency()
 *      Are the actual arguments potentially compatible with a
 *      polymorphic function?
 *
 * The argument consistency rules are:
 *
 * 1) All arguments declared ANYELEMENT must have the same datatype.
 * 2) All arguments declared ANYARRAY must have the same datatype,
 *    which must be a varlena array type.
 * 3) All arguments declared ANYRANGE must have the same datatype,
 *    which must be a range type.
 * 4) If there are arguments of both ANYELEMENT and ANYARRAY, make sure the
 *    actual ANYELEMENT datatype is in fact the element type for the actual
 *    ANYARRAY datatype.
 * 5) Similarly, if there are arguments of both ANYELEMENT and ANYRANGE,
 *    make sure the actual ANYELEMENT datatype is in fact the subtype for
 *    the actual ANYRANGE type.
 * 6) ANYENUM is treated the same as ANYELEMENT except that if it is used
 *    (alone or in combination with plain ANYELEMENT), we add the extra
 *    condition that the ANYELEMENT type must be an enum.
 * 7) ANYNONARRAY is treated the same as ANYELEMENT except that if it is used,
 *    we add the extra condition that the ANYELEMENT type must not be an array.
 *    (This is a no-op if used in combination with ANYARRAY or ANYENUM, but
 *    is an extra restriction if not.)
 *
 * Domains over arrays match ANYARRAY, and are immediately flattened to their
 * base type.  (Thus, for example, we will consider it a match if one ANYARRAY
 * argument is a domain over int4[] while another one is just int4[].)  Also
 * notice that such a domain does *not* match ANYNONARRAY.
 *
 * Similarly, domains over ranges match ANYRANGE, and are immediately
 * flattened to their base type.
 *
 * Note that domains aren't currently considered to match ANYENUM,
 * even if their base type would match.
 *
 * If we have UNKNOWN input (ie, an untyped literal) for any polymorphic
 * argument, assume it is okay.
 *
 * If an input is of type ANYARRAY (ie, we know it's an array, but not
 * what element type), we will accept it as a match to an argument declared
 * ANYARRAY, so long as we don't have to determine an element type ---
 * that is, so long as there is no use of ANYELEMENT.  This is mostly for
 * backwards compatibility with the pre-7.4 behavior of ANYARRAY.
 *
 * We do not ereport here, but just return false if a rule is violated.
 */
bool
check_generic_type_consistency(Oid *actual_arg_types,
                               Oid *declared_arg_types,
                               int nargs)
{
    int         j;
    Oid         elem_typeid = InvalidOid;
    Oid         array_typeid = InvalidOid;
    Oid         array_typelem;
    Oid         range_typeid = InvalidOid;
    Oid         range_typelem;
    bool        have_anyelement = false;
    bool        have_anynonarray = false;
    bool        have_anyenum = false;

    /*
     * Loop through the arguments to see if we have any that are polymorphic.
     * If so, require the actual types to be consistent.
     */
    for (j = 0; j < nargs; j++)
    {
        Oid         decl_type = declared_arg_types[j];
        Oid         actual_type = actual_arg_types[j];

        if (decl_type == ANYELEMENTOID ||
            decl_type == ANYNONARRAYOID ||
            decl_type == ANYENUMOID)
        {
            have_anyelement = true;
            if (decl_type == ANYNONARRAYOID)
                have_anynonarray = true;
            else if (decl_type == ANYENUMOID)
                have_anyenum = true;
            if (actual_type == UNKNOWNOID)
                continue;
            if (OidIsValid(elem_typeid) && actual_type != elem_typeid)
                return false;
            elem_typeid = actual_type;
        }
        else if (decl_type == ANYARRAYOID)
        {
            if (actual_type == UNKNOWNOID)
                continue;
            actual_type = getBaseType(actual_type); /* flatten domains */
            if (OidIsValid(array_typeid) && actual_type != array_typeid)
                return false;
            array_typeid = actual_type;
        }
        else if (decl_type == ANYRANGEOID)
        {
            if (actual_type == UNKNOWNOID)
                continue;
            actual_type = getBaseType(actual_type); /* flatten domains */
            if (OidIsValid(range_typeid) && actual_type != range_typeid)
                return false;
            range_typeid = actual_type;
        }
    }

    /* Get the element type based on the array type, if we have one */
    if (OidIsValid(array_typeid))
    {
        if (array_typeid == ANYARRAYOID)
        {
            /* Special case for ANYARRAY input: okay iff no ANYELEMENT */
            if (have_anyelement)
                return false;
            return true;
        }

        array_typelem = get_element_type(array_typeid);
        if (!OidIsValid(array_typelem))
            return false;       /* should be an array, but isn't */

        if (!OidIsValid(elem_typeid))
        {
            /*
             * if we don't have an element type yet, use the one we just got
             */
            elem_typeid = array_typelem;
        }
        else if (array_typelem != elem_typeid)
        {
            /* otherwise, they better match */
            return false;
        }
    }

    /* Get the element type based on the range type, if we have one */
    if (OidIsValid(range_typeid))
    {
        range_typelem = get_range_subtype(range_typeid);
        if (!OidIsValid(range_typelem))
            return false;       /* should be a range, but isn't */

        if (!OidIsValid(elem_typeid))
        {
            /*
             * if we don't have an element type yet, use the one we just got
             */
            elem_typeid = range_typelem;
        }
        else if (range_typelem != elem_typeid)
        {
            /* otherwise, they better match */
            return false;
        }
    }

    if (have_anynonarray)
    {
        /* require the element type to not be an array or domain over array */
        if (type_is_array_domain(elem_typeid))
            return false;
    }

    if (have_anyenum)
    {
        /* require the element type to be an enum */
        if (!type_is_enum(elem_typeid))
            return false;
    }

    /* Looks valid */
    return true;
}

/*
 * enforce_generic_type_consistency()
 *      Make sure a polymorphic function is legally callable, and
 *      deduce actual argument and result types.
 *
 * If any polymorphic pseudotype is used in a function's arguments or
 * return type, we make sure the actual data types are consistent with
 * each other.  The argument consistency rules are shown above for
 * check_generic_type_consistency().
 *
 * If we have UNKNOWN input (ie, an untyped literal) for any polymorphic
 * argument, we attempt to deduce the actual type it should have.  If
 * successful, we alter that position of declared_arg_types[] so that
 * make_fn_arguments will coerce the literal to the right thing.
 *
 * Rules are applied to the function's return type (possibly altering it)
 * if it is declared as a polymorphic type:
 *
 * 1) If return type is ANYARRAY, and any argument is ANYARRAY, use the
 *    argument's actual type as the function's return type.
 * 2) Similarly, if return type is ANYRANGE, and any argument is ANYRANGE,
 *    use the argument's actual type as the function's return type.
 * 3) If return type is ANYARRAY, no argument is ANYARRAY, but any argument is
 *    ANYELEMENT, use the actual type of the argument to determine the
 *    function's return type, i.e. the element type's corresponding array
 *    type.  (Note: similar behavior does not exist for ANYRANGE, because it's
 *    impossible to determine the range type from the subtype alone.)
 * 4) If return type is ANYARRAY, but no argument is ANYARRAY or ANYELEMENT,
 *    generate an error.  Similarly, if return type is ANYRANGE, but no
 *    argument is ANYRANGE, generate an error.  (These conditions are
 *    prevented by CREATE FUNCTION and therefore are not expected here.)
 * 5) If return type is ANYELEMENT, and any argument is ANYELEMENT, use the
 *    argument's actual type as the function's return type.
 * 6) If return type is ANYELEMENT, no argument is ANYELEMENT, but any argument
 *    is ANYARRAY or ANYRANGE, use the actual type of the argument to determine
 *    the function's return type, i.e. the array type's corresponding element
 *    type or the range type's corresponding subtype (or both, in which case
 *    they must match).
 * 7) If return type is ANYELEMENT, no argument is ANYELEMENT, ANYARRAY, or
 *    ANYRANGE, generate an error.  (This condition is prevented by CREATE
 *    FUNCTION and therefore is not expected here.)
 * 8) ANYENUM is treated the same as ANYELEMENT except that if it is used
 *    (alone or in combination with plain ANYELEMENT), we add the extra
 *    condition that the ANYELEMENT type must be an enum.
 * 9) ANYNONARRAY is treated the same as ANYELEMENT except that if it is used,
 *    we add the extra condition that the ANYELEMENT type must not be an array.
 *    (This is a no-op if used in combination with ANYARRAY or ANYENUM, but
 *    is an extra restriction if not.)
 *
 * Domains over arrays or ranges match ANYARRAY or ANYRANGE arguments,
 * respectively, and are immediately flattened to their base type. (In
 * particular, if the return type is also ANYARRAY or ANYRANGE, we'll set it
 * to the base type not the domain type.)
 *
 * When allow_poly is false, we are not expecting any of the actual_arg_types
 * to be polymorphic, and we should not return a polymorphic result type
 * either.  When allow_poly is true, it is okay to have polymorphic "actual"
 * arg types, and we can return ANYARRAY, ANYRANGE, or ANYELEMENT as the
 * result.  (This case is currently used only to check compatibility of an
 * aggregate's declaration with the underlying transfn.)
 *
 * A special case is that we could see ANYARRAY as an actual_arg_type even
 * when allow_poly is false (this is possible only because pg_statistic has
 * columns shown as anyarray in the catalogs).  We allow this to match a
 * declared ANYARRAY argument, but only if there is no ANYELEMENT argument
 * or result (since we can't determine a specific element type to match to
 * ANYELEMENT).  Note this means that functions taking ANYARRAY had better
 * behave sanely if applied to the pg_statistic columns; they can't just
 * assume that successive inputs are of the same actual element type.
 */
Oid
enforce_generic_type_consistency(Oid *actual_arg_types,
                                 Oid *declared_arg_types,
                                 int nargs,
                                 Oid rettype,
                                 bool allow_poly)
{
    int         j;
    bool        have_generics = false;
    bool        have_unknowns = false;
    Oid         elem_typeid = InvalidOid;
    Oid         array_typeid = InvalidOid;
    Oid         range_typeid = InvalidOid;
    Oid         array_typelem;
    Oid         range_typelem;
    bool        have_anyelement = (rettype == ANYELEMENTOID ||
                                   rettype == ANYNONARRAYOID ||
                                   rettype == ANYENUMOID);
    bool        have_anynonarray = (rettype == ANYNONARRAYOID);
    bool        have_anyenum = (rettype == ANYENUMOID);

    /*
     * Loop through the arguments to see if we have any that are polymorphic.
     * If so, require the actual types to be consistent.
     */
    for (j = 0; j < nargs; j++)
    {
        Oid         decl_type = declared_arg_types[j];
        Oid         actual_type = actual_arg_types[j];

        if (decl_type == ANYELEMENTOID ||
            decl_type == ANYNONARRAYOID ||
            decl_type == ANYENUMOID)
        {
            have_generics = have_anyelement = true;
            if (decl_type == ANYNONARRAYOID)
                have_anynonarray = true;
            else if (decl_type == ANYENUMOID)
                have_anyenum = true;
            if (actual_type == UNKNOWNOID)
            {
                have_unknowns = true;
                continue;
            }
            if (allow_poly && decl_type == actual_type)
                continue;       /* no new information here */
            if (OidIsValid(elem_typeid) && actual_type != elem_typeid)
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("arguments declared \"anyelement\" are not all alike"),
                         errdetail("%s versus %s",
                                   format_type_be(elem_typeid),
                                   format_type_be(actual_type))));
            elem_typeid = actual_type;
        }
        else if (decl_type == ANYARRAYOID)
        {
            have_generics = true;
            if (actual_type == UNKNOWNOID)
            {
                have_unknowns = true;
                continue;
            }
            if (allow_poly && decl_type == actual_type)
                continue;       /* no new information here */
            actual_type = getBaseType(actual_type); /* flatten domains */
            if (OidIsValid(array_typeid) && actual_type != array_typeid)
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("arguments declared \"anyarray\" are not all alike"),
                         errdetail("%s versus %s",
                                   format_type_be(array_typeid),
                                   format_type_be(actual_type))));
            array_typeid = actual_type;
        }
        else if (decl_type == ANYRANGEOID)
        {
            have_generics = true;
            if (actual_type == UNKNOWNOID)
            {
                have_unknowns = true;
                continue;
            }
            if (allow_poly && decl_type == actual_type)
                continue;       /* no new information here */
            actual_type = getBaseType(actual_type); /* flatten domains */
            if (OidIsValid(range_typeid) && actual_type != range_typeid)
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("arguments declared \"anyrange\" are not all alike"),
                         errdetail("%s versus %s",
                                   format_type_be(range_typeid),
                                   format_type_be(actual_type))));
            range_typeid = actual_type;
        }
    }

    /*
     * Fast Track: if none of the arguments are polymorphic, return the
     * unmodified rettype.  We assume it can't be polymorphic either.
     */
    if (!have_generics)
        return rettype;

    /* Get the element type based on the array type, if we have one */
    if (OidIsValid(array_typeid))
    {
        if (array_typeid == ANYARRAYOID && !have_anyelement)
        {
            /* Special case for ANYARRAY input: okay iff no ANYELEMENT */
            array_typelem = ANYELEMENTOID;
        }
        else
        {
            array_typelem = get_element_type(array_typeid);
            if (!OidIsValid(array_typelem))
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("argument declared %s is not an array but type %s",
                                "anyarray", format_type_be(array_typeid))));
        }

        if (!OidIsValid(elem_typeid))
        {
            /*
             * if we don't have an element type yet, use the one we just got
             */
            elem_typeid = array_typelem;
        }
        else if (array_typelem != elem_typeid)
        {
            /* otherwise, they better match */
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("argument declared %s is not consistent with argument declared %s",
                            "anyarray", "anyelement"),
                     errdetail("%s versus %s",
                               format_type_be(array_typeid),
                               format_type_be(elem_typeid))));
        }
    }

    /* Get the element type based on the range type, if we have one */
    if (OidIsValid(range_typeid))
    {
        if (range_typeid == ANYRANGEOID && !have_anyelement)
        {
            /* Special case for ANYRANGE input: okay iff no ANYELEMENT */
            range_typelem = ANYELEMENTOID;
        }
        else
        {
            range_typelem = get_range_subtype(range_typeid);
            if (!OidIsValid(range_typelem))
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("argument declared %s is not a range type but type %s",
                                "anyrange",
                                format_type_be(range_typeid))));
        }

        if (!OidIsValid(elem_typeid))
        {
            /*
             * if we don't have an element type yet, use the one we just got
             */
            elem_typeid = range_typelem;
        }
        else if (range_typelem != elem_typeid)
        {
            /* otherwise, they better match */
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("argument declared %s is not consistent with argument declared %s",
                            "anyrange", "anyelement"),
                     errdetail("%s versus %s",
                               format_type_be(range_typeid),
                               format_type_be(elem_typeid))));
        }
    }

    if (!OidIsValid(elem_typeid))
    {
        if (allow_poly)
        {
            elem_typeid = ANYELEMENTOID;
            array_typeid = ANYARRAYOID;
            range_typeid = ANYRANGEOID;
        }
        else
        {
            /* Only way to get here is if all the generic args are UNKNOWN */
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("could not determine polymorphic type because input has type %s",
                            "unknown")));
        }
    }

    if (have_anynonarray && elem_typeid != ANYELEMENTOID)
    {
        /* require the element type to not be an array or domain over array */
        if (type_is_array_domain(elem_typeid))
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("type matched to anynonarray is an array type: %s",
                            format_type_be(elem_typeid))));
    }

    if (have_anyenum && elem_typeid != ANYELEMENTOID)
    {
        /* require the element type to be an enum */
        if (!type_is_enum(elem_typeid))
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("type matched to anyenum is not an enum type: %s",
                            format_type_be(elem_typeid))));
    }

    /*
     * If we had any unknown inputs, re-scan to assign correct types
     */
    if (have_unknowns)
    {
        for (j = 0; j < nargs; j++)
        {
            Oid         decl_type = declared_arg_types[j];
            Oid         actual_type = actual_arg_types[j];

            if (actual_type != UNKNOWNOID)
                continue;

            if (decl_type == ANYELEMENTOID ||
                decl_type == ANYNONARRAYOID ||
                decl_type == ANYENUMOID)
                declared_arg_types[j] = elem_typeid;
            else if (decl_type == ANYARRAYOID)
            {
                if (!OidIsValid(array_typeid))
                {
                    array_typeid = get_array_type(elem_typeid);
                    if (!OidIsValid(array_typeid))
                        ereport(ERROR,
                                (errcode(ERRCODE_UNDEFINED_OBJECT),
                                 errmsg("could not find array type for data type %s",
                                        format_type_be(elem_typeid))));
                }
                declared_arg_types[j] = array_typeid;
            }
            else if (decl_type == ANYRANGEOID)
            {
                if (!OidIsValid(range_typeid))
                {
                    ereport(ERROR,
                            (errcode(ERRCODE_UNDEFINED_OBJECT),
                             errmsg("could not find range type for data type %s",
                                    format_type_be(elem_typeid))));
                }
                declared_arg_types[j] = range_typeid;
            }
        }
    }

    /* if we return ANYARRAY use the appropriate argument type */
    if (rettype == ANYARRAYOID)
    {
        if (!OidIsValid(array_typeid))
        {
            array_typeid = get_array_type(elem_typeid);
            if (!OidIsValid(array_typeid))
                ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_OBJECT),
                         errmsg("could not find array type for data type %s",
                                format_type_be(elem_typeid))));
        }
        return array_typeid;
    }

    /* if we return ANYRANGE use the appropriate argument type */
    if (rettype == ANYRANGEOID)
    {
        if (!OidIsValid(range_typeid))
        {
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("could not find range type for data type %s",
                            format_type_be(elem_typeid))));
        }
        return range_typeid;
    }

    /* if we return ANYELEMENT use the appropriate argument type */
    if (rettype == ANYELEMENTOID ||
        rettype == ANYNONARRAYOID ||
        rettype == ANYENUMOID)
        return elem_typeid;

    /* we don't return a generic type; send back the original return type */
    return rettype;
}

/*
 * resolve_generic_type()
 *      Deduce an individual actual datatype on the assumption that
 *      the rules for polymorphic types are being followed.
 *
 * declared_type is the declared datatype we want to resolve.
 * context_actual_type is the actual input datatype to some argument
 * that has declared datatype context_declared_type.
 *
 * If declared_type isn't polymorphic, we just return it.  Otherwise,
 * context_declared_type must be polymorphic, and we deduce the correct
 * return type based on the relationship of the two polymorphic types.
 */
Oid
resolve_generic_type(Oid declared_type,
                     Oid context_actual_type,
                     Oid context_declared_type)
{
    if (declared_type == ANYARRAYOID)
    {
        if (context_declared_type == ANYARRAYOID)
        {
            /*
             * Use actual type, but it must be an array; or if it's a domain
             * over array, use the base array type.
             */
            Oid         context_base_type = getBaseType(context_actual_type);
            Oid         array_typelem = get_element_type(context_base_type);

            if (!OidIsValid(array_typelem))
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("argument declared %s is not an array but type %s",
                                "anyarray", format_type_be(context_base_type))));
            return context_base_type;
        }
        else if (context_declared_type == ANYELEMENTOID ||
                 context_declared_type == ANYNONARRAYOID ||
                 context_declared_type == ANYENUMOID ||
                 context_declared_type == ANYRANGEOID)
        {
            /* Use the array type corresponding to actual type */
            Oid         array_typeid = get_array_type(context_actual_type);

            if (!OidIsValid(array_typeid))
                ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_OBJECT),
                         errmsg("could not find array type for data type %s",
                                format_type_be(context_actual_type))));
            return array_typeid;
        }
    }
    else if (declared_type == ANYELEMENTOID ||
             declared_type == ANYNONARRAYOID ||
             declared_type == ANYENUMOID ||
             declared_type == ANYRANGEOID)
    {
        if (context_declared_type == ANYARRAYOID)
        {
            /* Use the element type corresponding to actual type */
            Oid         context_base_type = getBaseType(context_actual_type);
            Oid         array_typelem = get_element_type(context_base_type);

            if (!OidIsValid(array_typelem))
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("argument declared %s is not an array but type %s",
                                "anyarray", format_type_be(context_base_type))));
            return array_typelem;
        }
        else if (context_declared_type == ANYRANGEOID)
        {
            /* Use the element type corresponding to actual type */
            Oid         context_base_type = getBaseType(context_actual_type);
            Oid         range_typelem = get_range_subtype(context_base_type);

            if (!OidIsValid(range_typelem))
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("argument declared %s is not a range type but type %s",
                                "anyrange", format_type_be(context_base_type))));
            return range_typelem;
        }
        else if (context_declared_type == ANYELEMENTOID ||
                 context_declared_type == ANYNONARRAYOID ||
                 context_declared_type == ANYENUMOID)
        {
            /* Use the actual type; it doesn't matter if array or not */
            return context_actual_type;
        }
    }
    else
    {
        /* declared_type isn't polymorphic, so return it as-is */
        return declared_type;
    }
    /* If we get here, declared_type is polymorphic and context isn't */
    /* NB: this is a calling-code logic error, not a user error */
    elog(ERROR, "could not determine polymorphic type because context isn't polymorphic");
    return InvalidOid;          /* keep compiler quiet */
}


/* TypeCategory()
 *      Assign a category to the specified type OID.
 *
 * NB: this must not return TYPCATEGORY_INVALID.
 */
TYPCATEGORY
TypeCategory(Oid type)
{
    char        typcategory;
    bool        typispreferred;

    get_type_category_preferred(type, &typcategory, &typispreferred);
    Assert(typcategory != TYPCATEGORY_INVALID);
    return (TYPCATEGORY) typcategory;
}


/* IsPreferredType()
 *      Check if this type is a preferred type for the given category.
 *
 * If category is TYPCATEGORY_INVALID, then we'll return true for preferred
 * types of any category; otherwise, only for preferred types of that
 * category.
 */
bool
IsPreferredType(TYPCATEGORY category, Oid type)
{
    char        typcategory;
    bool        typispreferred;

    get_type_category_preferred(type, &typcategory, &typispreferred);
    if (category == typcategory || category == TYPCATEGORY_INVALID)
        return typispreferred;
    else
        return false;
}


/* IsBinaryCoercible()
 *      Check if srctype is binary-coercible to targettype.
 *
 * This notion allows us to cheat and directly exchange values without
 * going through the trouble of calling a conversion function.  Note that
 * in general, this should only be an implementation shortcut.  Before 7.4,
 * this was also used as a heuristic for resolving overloaded functions and
 * operators, but that's basically a bad idea.
 *
 * As of 7.3, binary coercibility isn't hardwired into the code anymore.
 * We consider two types binary-coercible if there is an implicitly
 * invokable, no-function-needed pg_cast entry.  Also, a domain is always
 * binary-coercible to its base type, though *not* vice versa (in the other
 * direction, one must apply domain constraint checks before accepting the
 * value as legitimate).  We also need to special-case various polymorphic
 * types.
 *
 * This function replaces IsBinaryCompatible(), which was an inherently
 * symmetric test.  Since the pg_cast entries aren't necessarily symmetric,
 * the order of the operands is now significant.
 */
bool
IsBinaryCoercible(Oid srctype, Oid targettype)
{
    HeapTuple   tuple;
    Form_pg_cast castForm;
    bool        result;

    /* Fast path if same type */
    if (srctype == targettype)
        return true;

    /* Anything is coercible to ANY or ANYELEMENT */
    if (targettype == ANYOID || targettype == ANYELEMENTOID)
        return true;

    /* If srctype is a domain, reduce to its base type */
    if (OidIsValid(srctype))
        srctype = getBaseType(srctype);

    /* Somewhat-fast path for domain -> base type case */
    if (srctype == targettype)
        return true;

    /* Also accept any array type as coercible to ANYARRAY */
    if (targettype == ANYARRAYOID)
        if (type_is_array(srctype))
            return true;

    /* Also accept any non-array type as coercible to ANYNONARRAY */
    if (targettype == ANYNONARRAYOID)
        if (!type_is_array(srctype))
            return true;

    /* Also accept any enum type as coercible to ANYENUM */
    if (targettype == ANYENUMOID)
        if (type_is_enum(srctype))
            return true;

    /* Also accept any range type as coercible to ANYRANGE */
    if (targettype == ANYRANGEOID)
        if (type_is_range(srctype))
            return true;

    /* Also accept any composite type as coercible to RECORD */
    if (targettype == RECORDOID)
        if (ISCOMPLEX(srctype))
            return true;

    /* Also accept any composite array type as coercible to RECORD[] */
    if (targettype == RECORDARRAYOID)
        if (is_complex_array(srctype))
            return true;

    /* Else look in pg_cast */
    tuple = SearchSysCache2(CASTSOURCETARGET,
                            ObjectIdGetDatum(srctype),
                            ObjectIdGetDatum(targettype));
    if (!HeapTupleIsValid(tuple))
        return false;           /* no cast */
    castForm = (Form_pg_cast) GETSTRUCT(tuple);

    result = (castForm->castmethod == COERCION_METHOD_BINARY &&
              castForm->castcontext == COERCION_CODE_IMPLICIT);

    ReleaseSysCache(tuple);

    return result;
}


/*
 * find_coercion_pathway
 *      Look for a coercion pathway between two types.
 *
 * Currently, this deals only with scalar-type cases; it does not consider
 * polymorphic types nor casts between composite types.  (Perhaps fold
 * those in someday?)
 *
 * ccontext determines the set of available casts.
 *
 * The possible result codes are:
 *  COERCION_PATH_NONE: failed to find any coercion pathway
 *              *funcid is set to InvalidOid
 *  COERCION_PATH_FUNC: apply the coercion function returned in *funcid
 *  COERCION_PATH_RELABELTYPE: binary-compatible cast, no function needed
 *              *funcid is set to InvalidOid
 *  COERCION_PATH_ARRAYCOERCE: need an ArrayCoerceExpr node
 *              *funcid is set to InvalidOid
 *  COERCION_PATH_COERCEVIAIO: need a CoerceViaIO node
 *              *funcid is set to InvalidOid
 *
 * Note: COERCION_PATH_RELABELTYPE does not necessarily mean that no work is
 * needed to do the coercion; if the target is a domain then we may need to
 * apply domain constraint checking.  If you want to check for a zero-effort
 * conversion then use IsBinaryCoercible().
 */
CoercionPathType
find_coercion_pathway(Oid targetTypeId, Oid sourceTypeId,
                      CoercionContext ccontext,
                      Oid *funcid)
{
    CoercionPathType result = COERCION_PATH_NONE;
    HeapTuple   tuple;

    *funcid = InvalidOid;

    /* Perhaps the types are domains; if so, look at their base types */
    if (OidIsValid(sourceTypeId))
        sourceTypeId = getBaseType(sourceTypeId);
    if (OidIsValid(targetTypeId))
        targetTypeId = getBaseType(targetTypeId);

    /* Domains are always coercible to and from their base type */
    if (sourceTypeId == targetTypeId)
        return COERCION_PATH_RELABELTYPE;

    /* Look in pg_cast */
    tuple = SearchSysCache2(CASTSOURCETARGET,
                            ObjectIdGetDatum(sourceTypeId),
                            ObjectIdGetDatum(targetTypeId));

    if (HeapTupleIsValid(tuple))
    {
        Form_pg_cast castForm = (Form_pg_cast) GETSTRUCT(tuple);
        CoercionContext castcontext;

        /* convert char value for castcontext to CoercionContext enum */
        switch (castForm->castcontext)
        {
            case COERCION_CODE_IMPLICIT:
                castcontext = COERCION_IMPLICIT;
                break;
            case COERCION_CODE_ASSIGNMENT:
                castcontext = COERCION_ASSIGNMENT;
                break;
            case COERCION_CODE_EXPLICIT:
                castcontext = COERCION_EXPLICIT;
                break;
            default:
                elog(ERROR, "unrecognized castcontext: %d",
                     (int) castForm->castcontext);
                castcontext = 0;    /* keep compiler quiet */
                break;
        }

        /* Rely on ordering of enum for correct behavior here */
        if (ccontext >= castcontext)
        {
            switch (castForm->castmethod)
            {
                case COERCION_METHOD_FUNCTION:
                    result = COERCION_PATH_FUNC;
                    *funcid = castForm->castfunc;
                    break;
                case COERCION_METHOD_INOUT:
                    result = COERCION_PATH_COERCEVIAIO;
                    break;
                case COERCION_METHOD_BINARY:
                    result = COERCION_PATH_RELABELTYPE;
                    break;
                default:
                    elog(ERROR, "unrecognized castmethod: %d",
                         (int) castForm->castmethod);
                    break;
            }
        }

        ReleaseSysCache(tuple);
    }
    else
    {
        /*
         * If there's no pg_cast entry, perhaps we are dealing with a pair of
         * array types.  If so, and if their element types have a conversion
         * pathway, report that we can coerce with an ArrayCoerceExpr.
         *
         * Hack: disallow coercions to oidvector and int2vector, which
         * otherwise tend to capture coercions that should go to "real" array
         * types.  We want those types to be considered "real" arrays for many
         * purposes, but not this one.  (Also, ArrayCoerceExpr isn't
         * guaranteed to produce an output that meets the restrictions of
         * these datatypes, such as being 1-dimensional.)
         */
        if (targetTypeId != OIDVECTOROID && targetTypeId != INT2VECTOROID)
        {
            Oid         targetElem;
            Oid         sourceElem;

            if ((targetElem = get_element_type(targetTypeId)) != InvalidOid &&
                (sourceElem = get_element_type(sourceTypeId)) != InvalidOid)
            {
                CoercionPathType elempathtype;
                Oid         elemfuncid;

                elempathtype = find_coercion_pathway(targetElem,
                                                     sourceElem,
                                                     ccontext,
                                                     &elemfuncid);
                if (elempathtype != COERCION_PATH_NONE)
                {
                    result = COERCION_PATH_ARRAYCOERCE;
                }
            }
        }

        /*
         * If we still haven't found a possibility, consider automatic casting
         * using I/O functions.  We allow assignment casts to string types and
         * explicit casts from string types to be handled this way. (The
         * CoerceViaIO mechanism is a lot more general than that, but this is
         * all we want to allow in the absence of a pg_cast entry.) It would
         * probably be better to insist on explicit casts in both directions,
         * but this is a compromise to preserve something of the pre-8.3
         * behavior that many types had implicit (yipes!) casts to text.
         */
        if (result == COERCION_PATH_NONE)
        {
            if (ccontext >= COERCION_ASSIGNMENT &&
                TypeCategory(targetTypeId) == TYPCATEGORY_STRING)
                result = COERCION_PATH_COERCEVIAIO;
            else if (ccontext >= COERCION_EXPLICIT &&
                     TypeCategory(sourceTypeId) == TYPCATEGORY_STRING)
                result = COERCION_PATH_COERCEVIAIO;
        }
    }

    return result;
}


/*
 * find_typmod_coercion_function -- does the given type need length coercion?
 *
 * If the target type possesses a pg_cast function from itself to itself,
 * it must need length coercion.
 *
 * "bpchar" (ie, char(N)) and "numeric" are examples of such types.
 *
 * If the given type is a varlena array type, we do not look for a coercion
 * function associated directly with the array type, but instead look for
 * one associated with the element type.  An ArrayCoerceExpr node must be
 * used to apply such a function.  (Note: currently, it's pointless to
 * return the funcid in this case, because it'll just get looked up again
 * in the recursive construction of the ArrayCoerceExpr's elemexpr.)
 *
 * We use the same result enum as find_coercion_pathway, but the only possible
 * result codes are:
 *  COERCION_PATH_NONE: no length coercion needed
 *  COERCION_PATH_FUNC: apply the function returned in *funcid
 *  COERCION_PATH_ARRAYCOERCE: apply the function using ArrayCoerceExpr
 */
CoercionPathType
find_typmod_coercion_function(Oid typeId,
                              Oid *funcid)
{
    CoercionPathType result;
    Type        targetType;
    Form_pg_type typeForm;
    HeapTuple   tuple;

    *funcid = InvalidOid;
    result = COERCION_PATH_FUNC;

    targetType = typeidType(typeId);
    typeForm = (Form_pg_type) GETSTRUCT(targetType);

    /* Check for a varlena array type */
    if (typeForm->typelem != InvalidOid && typeForm->typlen == -1)
    {
        /* Yes, switch our attention to the element type */
        typeId = typeForm->typelem;
        result = COERCION_PATH_ARRAYCOERCE;
    }
    ReleaseSysCache(targetType);

    /* Look in pg_cast */
    tuple = SearchSysCache2(CASTSOURCETARGET,
                            ObjectIdGetDatum(typeId),
                            ObjectIdGetDatum(typeId));

    if (HeapTupleIsValid(tuple))
    {
        Form_pg_cast castForm = (Form_pg_cast) GETSTRUCT(tuple);

        *funcid = castForm->castfunc;
        ReleaseSysCache(tuple);
    }

    if (!OidIsValid(*funcid))
        result = COERCION_PATH_NONE;

    return result;
}

/*
 * is_complex_array
 *      Is this type an array of composite?
 *
 * Note: this will not return true for record[]; check for RECORDARRAYOID
 * separately if needed.
 */
static bool
is_complex_array(Oid typid)
{
    Oid         elemtype = get_element_type(typid);

    return (OidIsValid(elemtype) && ISCOMPLEX(elemtype));
}


/*
 * Check whether reltypeId is the row type of a typed table of type
 * reloftypeId, or is a domain over such a row type.  (This is conceptually
 * similar to the subtype relationship checked by typeInheritsFrom().)
 */
static bool
typeIsOfTypedTable(Oid reltypeId, Oid reloftypeId)
{
    Oid         relid = typeOrDomainTypeRelid(reltypeId);
    bool        result = false;

    if (relid)
    {
        HeapTuple   tp;
        Form_pg_class reltup;

        tp = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
        if (!HeapTupleIsValid(tp))
            elog(ERROR, "cache lookup failed for relation %u", relid);

        reltup = (Form_pg_class) GETSTRUCT(tp);
        if (reltup->reloftype == reloftypeId)
            result = true;

        ReleaseSysCache(tp);
    }

    return result;
}