parse_expr.c

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/*-------------------------------------------------------------------------
 *
 * parse_expr.c
 *    handle expressions in parser
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/parser/parse_expr.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "catalog/pg_type.h"
#include "commands/dbcommands.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/var.h"
#include "parser/analyze.h"
#include "parser/parse_coerce.h"
#include "parser/parse_collate.h"
#include "parser/parse_expr.h"
#include "parser/parse_func.h"
#include "parser/parse_oper.h"
#include "parser/parse_relation.h"
#include "parser/parse_target.h"
#include "parser/parse_type.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/xml.h"


bool        Transform_null_equals = false;

static Node *transformExprRecurse(ParseState *pstate, Node *expr);
static Node *transformParamRef(ParseState *pstate, ParamRef *pref);
static Node *transformAExprOp(ParseState *pstate, A_Expr *a);
static Node *transformAExprAnd(ParseState *pstate, A_Expr *a);
static Node *transformAExprOr(ParseState *pstate, A_Expr *a);
static Node *transformAExprNot(ParseState *pstate, A_Expr *a);
static Node *transformAExprOpAny(ParseState *pstate, A_Expr *a);
static Node *transformAExprOpAll(ParseState *pstate, A_Expr *a);
static Node *transformAExprDistinct(ParseState *pstate, A_Expr *a);
static Node *transformAExprNullIf(ParseState *pstate, A_Expr *a);
static Node *transformAExprOf(ParseState *pstate, A_Expr *a);
static Node *transformAExprIn(ParseState *pstate, A_Expr *a);
static Node *transformFuncCall(ParseState *pstate, FuncCall *fn);
static Node *transformCaseExpr(ParseState *pstate, CaseExpr *c);
static Node *transformSubLink(ParseState *pstate, SubLink *sublink);
static Node *transformArrayExpr(ParseState *pstate, A_ArrayExpr *a,
                   Oid array_type, Oid element_type, int32 typmod);
static Node *transformRowExpr(ParseState *pstate, RowExpr *r);
static Node *transformCoalesceExpr(ParseState *pstate, CoalesceExpr *c);
static Node *transformMinMaxExpr(ParseState *pstate, MinMaxExpr *m);
static Node *transformXmlExpr(ParseState *pstate, XmlExpr *x);
static Node *transformXmlSerialize(ParseState *pstate, XmlSerialize *xs);
static Node *transformBooleanTest(ParseState *pstate, BooleanTest *b);
static Node *transformCurrentOfExpr(ParseState *pstate, CurrentOfExpr *cexpr);
static Node *transformColumnRef(ParseState *pstate, ColumnRef *cref);
static Node *transformWholeRowRef(ParseState *pstate, RangeTblEntry *rte,
                     int location);
static Node *transformIndirection(ParseState *pstate, Node *basenode,
                     List *indirection);
static Node *transformTypeCast(ParseState *pstate, TypeCast *tc);
static Node *transformCollateClause(ParseState *pstate, CollateClause *c);
static Node *make_row_comparison_op(ParseState *pstate, List *opname,
                       List *largs, List *rargs, int location);
static Node *make_row_distinct_op(ParseState *pstate, List *opname,
                     RowExpr *lrow, RowExpr *rrow, int location);
static Expr *make_distinct_op(ParseState *pstate, List *opname,
                 Node *ltree, Node *rtree, int location);


/*
 * transformExpr -
 *    Analyze and transform expressions. Type checking and type casting is
 *    done here. The optimizer and the executor cannot handle the original
 *    (raw) expressions collected by the parse tree. Hence the transformation
 *    here.
 *
 * NOTE: there are various cases in which this routine will get applied to
 * an already-transformed expression.  Some examples:
 *  1. At least one construct (BETWEEN/AND) puts the same nodes
 *  into two branches of the parse tree; hence, some nodes
 *  are transformed twice.
 *  2. Another way it can happen is that coercion of an operator or
 *  function argument to the required type (via coerce_type())
 *  can apply transformExpr to an already-transformed subexpression.
 *  An example here is "SELECT count(*) + 1.0 FROM table".
 *  3. CREATE TABLE t1 (LIKE t2 INCLUDING INDEXES) can pass in
 *  already-transformed index expressions.
 * While it might be possible to eliminate these cases, the path of
 * least resistance so far has been to ensure that transformExpr() does
 * no damage if applied to an already-transformed tree.  This is pretty
 * easy for cases where the transformation replaces one node type with
 * another, such as A_Const => Const; we just do nothing when handed
 * a Const.  More care is needed for node types that are used as both
 * input and output of transformExpr; see SubLink for example.
 */
Node *
transformExpr(ParseState *pstate, Node *expr, ParseExprKind exprKind)
{
    Node       *result;
    ParseExprKind sv_expr_kind;

    /* Save and restore identity of expression type we're parsing */
    Assert(exprKind != EXPR_KIND_NONE);
    sv_expr_kind = pstate->p_expr_kind;
    pstate->p_expr_kind = exprKind;

    result = transformExprRecurse(pstate, expr);

    pstate->p_expr_kind = sv_expr_kind;

    return result;
}

static Node *
transformExprRecurse(ParseState *pstate, Node *expr)
{
    Node       *result;

    if (expr == NULL)
        return NULL;

    /* Guard against stack overflow due to overly complex expressions */
    check_stack_depth();

    switch (nodeTag(expr))
    {
        case T_ColumnRef:
            result = transformColumnRef(pstate, (ColumnRef *) expr);
            break;

        case T_ParamRef:
            result = transformParamRef(pstate, (ParamRef *) expr);
            break;

        case T_A_Const:
            {
                A_Const    *con = (A_Const *) expr;
                Value      *val = &con->val;

                result = (Node *) make_const(pstate, val, con->location);
                break;
            }

        case T_A_Indirection:
            {
                A_Indirection *ind = (A_Indirection *) expr;

                result = transformExprRecurse(pstate, ind->arg);
                result = transformIndirection(pstate, result,
                                              ind->indirection);
                break;
            }

        case T_A_ArrayExpr:
            result = transformArrayExpr(pstate, (A_ArrayExpr *) expr,
                                        InvalidOid, InvalidOid, -1);
            break;

        case T_TypeCast:
            {
                TypeCast   *tc = (TypeCast *) expr;

                /*
                 * If the subject of the typecast is an ARRAY[] construct and
                 * the target type is an array type, we invoke
                 * transformArrayExpr() directly so that we can pass down the
                 * type information.  This avoids some cases where
                 * transformArrayExpr() might not infer the correct type.
                 */
                if (IsA(tc->arg, A_ArrayExpr))
                {
                    Oid         targetType;
                    Oid         elementType;
                    int32       targetTypmod;

                    typenameTypeIdAndMod(pstate, tc->typeName,
                                         &targetType, &targetTypmod);

                    /*
                     * If target is a domain over array, work with the base
                     * array type here.  transformTypeCast below will cast the
                     * array type to the domain.  In the usual case that the
                     * target is not a domain, transformTypeCast is a no-op.
                     */
                    targetType = getBaseTypeAndTypmod(targetType,
                                                      &targetTypmod);
                    elementType = get_element_type(targetType);
                    if (OidIsValid(elementType))
                    {
                        tc = copyObject(tc);
                        tc->arg = transformArrayExpr(pstate,
                                                     (A_ArrayExpr *) tc->arg,
                                                     targetType,
                                                     elementType,
                                                     targetTypmod);
                    }
                }

                result = transformTypeCast(pstate, tc);
                break;
            }

        case T_CollateClause:
            result = transformCollateClause(pstate, (CollateClause *) expr);
            break;

        case T_A_Expr:
            {
                A_Expr     *a = (A_Expr *) expr;

                switch (a->kind)
                {
                    case AEXPR_OP:
                        result = transformAExprOp(pstate, a);
                        break;
                    case AEXPR_AND:
                        result = transformAExprAnd(pstate, a);
                        break;
                    case AEXPR_OR:
                        result = transformAExprOr(pstate, a);
                        break;
                    case AEXPR_NOT:
                        result = transformAExprNot(pstate, a);
                        break;
                    case AEXPR_OP_ANY:
                        result = transformAExprOpAny(pstate, a);
                        break;
                    case AEXPR_OP_ALL:
                        result = transformAExprOpAll(pstate, a);
                        break;
                    case AEXPR_DISTINCT:
                        result = transformAExprDistinct(pstate, a);
                        break;
                    case AEXPR_NULLIF:
                        result = transformAExprNullIf(pstate, a);
                        break;
                    case AEXPR_OF:
                        result = transformAExprOf(pstate, a);
                        break;
                    case AEXPR_IN:
                        result = transformAExprIn(pstate, a);
                        break;
                    default:
                        elog(ERROR, "unrecognized A_Expr kind: %d", a->kind);
                        result = NULL;      /* keep compiler quiet */
                        break;
                }
                break;
            }

        case T_FuncCall:
            result = transformFuncCall(pstate, (FuncCall *) expr);
            break;

        case T_NamedArgExpr:
            {
                NamedArgExpr *na = (NamedArgExpr *) expr;

                na->arg = (Expr *) transformExprRecurse(pstate, (Node *) na->arg);
                result = expr;
                break;
            }

        case T_SubLink:
            result = transformSubLink(pstate, (SubLink *) expr);
            break;

        case T_CaseExpr:
            result = transformCaseExpr(pstate, (CaseExpr *) expr);
            break;

        case T_RowExpr:
            result = transformRowExpr(pstate, (RowExpr *) expr);
            break;

        case T_CoalesceExpr:
            result = transformCoalesceExpr(pstate, (CoalesceExpr *) expr);
            break;

        case T_MinMaxExpr:
            result = transformMinMaxExpr(pstate, (MinMaxExpr *) expr);
            break;

        case T_XmlExpr:
            result = transformXmlExpr(pstate, (XmlExpr *) expr);
            break;

        case T_XmlSerialize:
            result = transformXmlSerialize(pstate, (XmlSerialize *) expr);
            break;

        case T_NullTest:
            {
                NullTest   *n = (NullTest *) expr;

                n->arg = (Expr *) transformExprRecurse(pstate, (Node *) n->arg);
                /* the argument can be any type, so don't coerce it */
                n->argisrow = type_is_rowtype(exprType((Node *) n->arg));
                result = expr;
                break;
            }

        case T_BooleanTest:
            result = transformBooleanTest(pstate, (BooleanTest *) expr);
            break;

        case T_CurrentOfExpr:
            result = transformCurrentOfExpr(pstate, (CurrentOfExpr *) expr);
            break;

            /*********************************************
             * Quietly accept node types that may be presented when we are
             * called on an already-transformed tree.
             *
             * Do any other node types need to be accepted?  For now we are
             * taking a conservative approach, and only accepting node
             * types that are demonstrably necessary to accept.
             *********************************************/
        case T_Var:
        case T_Const:
        case T_Param:
        case T_Aggref:
        case T_WindowFunc:
        case T_ArrayRef:
        case T_FuncExpr:
        case T_OpExpr:
        case T_DistinctExpr:
        case T_NullIfExpr:
        case T_ScalarArrayOpExpr:
        case T_BoolExpr:
        case T_FieldSelect:
        case T_FieldStore:
        case T_RelabelType:
        case T_CoerceViaIO:
        case T_ArrayCoerceExpr:
        case T_ConvertRowtypeExpr:
        case T_CollateExpr:
        case T_CaseTestExpr:
        case T_ArrayExpr:
        case T_CoerceToDomain:
        case T_CoerceToDomainValue:
        case T_SetToDefault:
            {
                result = (Node *) expr;
                break;
            }

        default:
            /* should not reach here */
            elog(ERROR, "unrecognized node type: %d", (int) nodeTag(expr));
            result = NULL;      /* keep compiler quiet */
            break;
    }

    return result;
}

/*
 * helper routine for delivering "column does not exist" error message
 *
 * (Usually we don't have to work this hard, but the general case of field
 * selection from an arbitrary node needs it.)
 */
static void
unknown_attribute(ParseState *pstate, Node *relref, char *attname,
                  int location)
{
    RangeTblEntry *rte;

    if (IsA(relref, Var) &&
        ((Var *) relref)->varattno == InvalidAttrNumber)
    {
        /* Reference the RTE by alias not by actual table name */
        rte = GetRTEByRangeTablePosn(pstate,
                                     ((Var *) relref)->varno,
                                     ((Var *) relref)->varlevelsup);
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_COLUMN),
                 errmsg("column %s.%s does not exist",
                        rte->eref->aliasname, attname),
                 parser_errposition(pstate, location)));
    }
    else
    {
        /* Have to do it by reference to the type of the expression */
        Oid         relTypeId = exprType(relref);

        if (ISCOMPLEX(relTypeId))
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_COLUMN),
                     errmsg("column \"%s\" not found in data type %s",
                            attname, format_type_be(relTypeId)),
                     parser_errposition(pstate, location)));
        else if (relTypeId == RECORDOID)
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_COLUMN),
               errmsg("could not identify column \"%s\" in record data type",
                      attname),
                     parser_errposition(pstate, location)));
        else
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("column notation .%s applied to type %s, "
                            "which is not a composite type",
                            attname, format_type_be(relTypeId)),
                     parser_errposition(pstate, location)));
    }
}

static Node *
transformIndirection(ParseState *pstate, Node *basenode, List *indirection)
{
    Node       *result = basenode;
    List       *subscripts = NIL;
    int         location = exprLocation(basenode);
    ListCell   *i;

    /*
     * We have to split any field-selection operations apart from
     * subscripting.  Adjacent A_Indices nodes have to be treated as a single
     * multidimensional subscript operation.
     */
    foreach(i, indirection)
    {
        Node       *n = lfirst(i);

        if (IsA(n, A_Indices))
            subscripts = lappend(subscripts, n);
        else if (IsA(n, A_Star))
        {
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("row expansion via \"*\" is not supported here"),
                     parser_errposition(pstate, location)));
        }
        else
        {
            Node       *newresult;

            Assert(IsA(n, String));

            /* process subscripts before this field selection */
            if (subscripts)
                result = (Node *) transformArraySubscripts(pstate,
                                                           result,
                                                           exprType(result),
                                                           InvalidOid,
                                                           exprTypmod(result),
                                                           subscripts,
                                                           NULL);
            subscripts = NIL;

            newresult = ParseFuncOrColumn(pstate,
                                          list_make1(n),
                                          list_make1(result),
                                          NIL, false, false, false,
                                          NULL, true, location);
            if (newresult == NULL)
                unknown_attribute(pstate, result, strVal(n), location);
            result = newresult;
        }
    }
    /* process trailing subscripts, if any */
    if (subscripts)
        result = (Node *) transformArraySubscripts(pstate,
                                                   result,
                                                   exprType(result),
                                                   InvalidOid,
                                                   exprTypmod(result),
                                                   subscripts,
                                                   NULL);

    return result;
}

/*
 * Transform a ColumnRef.
 *
 * If you find yourself changing this code, see also ExpandColumnRefStar.
 */
static Node *
transformColumnRef(ParseState *pstate, ColumnRef *cref)
{
    Node       *node = NULL;
    char       *nspname = NULL;
    char       *relname = NULL;
    char       *colname = NULL;
    RangeTblEntry *rte;
    int         levels_up;
    enum
    {
        CRERR_NO_COLUMN,
        CRERR_NO_RTE,
        CRERR_WRONG_DB,
        CRERR_TOO_MANY
    }           crerr = CRERR_NO_COLUMN;

    /*
     * Give the PreParseColumnRefHook, if any, first shot.  If it returns
     * non-null then that's all, folks.
     */
    if (pstate->p_pre_columnref_hook != NULL)
    {
        node = (*pstate->p_pre_columnref_hook) (pstate, cref);
        if (node != NULL)
            return node;
    }

    /*----------
     * The allowed syntaxes are:
     *
     * A        First try to resolve as unqualified column name;
     *          if no luck, try to resolve as unqualified table name (A.*).
     * A.B      A is an unqualified table name; B is either a
     *          column or function name (trying column name first).
     * A.B.C    schema A, table B, col or func name C.
     * A.B.C.D  catalog A, schema B, table C, col or func D.
     * A.*      A is an unqualified table name; means whole-row value.
     * A.B.*    whole-row value of table B in schema A.
     * A.B.C.*  whole-row value of table C in schema B in catalog A.
     *
     * We do not need to cope with bare "*"; that will only be accepted by
     * the grammar at the top level of a SELECT list, and transformTargetList
     * will take care of it before it ever gets here.  Also, "A.*" etc will
     * be expanded by transformTargetList if they appear at SELECT top level,
     * so here we are only going to see them as function or operator inputs.
     *
     * Currently, if a catalog name is given then it must equal the current
     * database name; we check it here and then discard it.
     *----------
     */
    switch (list_length(cref->fields))
    {
        case 1:
            {
                Node       *field1 = (Node *) linitial(cref->fields);

                Assert(IsA(field1, String));
                colname = strVal(field1);

                /* Try to identify as an unqualified column */
                node = colNameToVar(pstate, colname, false, cref->location);

                if (node == NULL)
                {
                    /*
                     * Not known as a column of any range-table entry.
                     *
                     * Consider the possibility that it's VALUE in a domain
                     * check expression.  (We handle VALUE as a name, not a
                     * keyword, to avoid breaking a lot of applications that
                     * have used VALUE as a column name in the past.)
                     */
                    if (pstate->p_value_substitute != NULL &&
                        strcmp(colname, "value") == 0)
                    {
                        node = (Node *) copyObject(pstate->p_value_substitute);

                        /*
                         * Try to propagate location knowledge.  This should
                         * be extended if p_value_substitute can ever take on
                         * other node types.
                         */
                        if (IsA(node, CoerceToDomainValue))
                            ((CoerceToDomainValue *) node)->location = cref->location;
                        break;
                    }

                    /*
                     * Try to find the name as a relation.  Note that only
                     * relations already entered into the rangetable will be
                     * recognized.
                     *
                     * This is a hack for backwards compatibility with
                     * PostQUEL-inspired syntax.  The preferred form now is
                     * "rel.*".
                     */
                    rte = refnameRangeTblEntry(pstate, NULL, colname,
                                               cref->location,
                                               &levels_up);
                    if (rte)
                        node = transformWholeRowRef(pstate, rte,
                                                    cref->location);
                }
                break;
            }
        case 2:
            {
                Node       *field1 = (Node *) linitial(cref->fields);
                Node       *field2 = (Node *) lsecond(cref->fields);

                Assert(IsA(field1, String));
                relname = strVal(field1);

                /* Locate the referenced RTE */
                rte = refnameRangeTblEntry(pstate, nspname, relname,
                                           cref->location,
                                           &levels_up);
                if (rte == NULL)
                {
                    crerr = CRERR_NO_RTE;
                    break;
                }

                /* Whole-row reference? */
                if (IsA(field2, A_Star))
                {
                    node = transformWholeRowRef(pstate, rte, cref->location);
                    break;
                }

                Assert(IsA(field2, String));
                colname = strVal(field2);

                /* Try to identify as a column of the RTE */
                node = scanRTEForColumn(pstate, rte, colname, cref->location);
                if (node == NULL)
                {
                    /* Try it as a function call on the whole row */
                    node = transformWholeRowRef(pstate, rte, cref->location);
                    node = ParseFuncOrColumn(pstate,
                                             list_make1(makeString(colname)),
                                             list_make1(node),
                                             NIL, false, false, false,
                                             NULL, true, cref->location);
                }
                break;
            }
        case 3:
            {
                Node       *field1 = (Node *) linitial(cref->fields);
                Node       *field2 = (Node *) lsecond(cref->fields);
                Node       *field3 = (Node *) lthird(cref->fields);

                Assert(IsA(field1, String));
                nspname = strVal(field1);
                Assert(IsA(field2, String));
                relname = strVal(field2);

                /* Locate the referenced RTE */
                rte = refnameRangeTblEntry(pstate, nspname, relname,
                                           cref->location,
                                           &levels_up);
                if (rte == NULL)
                {
                    crerr = CRERR_NO_RTE;
                    break;
                }

                /* Whole-row reference? */
                if (IsA(field3, A_Star))
                {
                    node = transformWholeRowRef(pstate, rte, cref->location);
                    break;
                }

                Assert(IsA(field3, String));
                colname = strVal(field3);

                /* Try to identify as a column of the RTE */
                node = scanRTEForColumn(pstate, rte, colname, cref->location);
                if (node == NULL)
                {
                    /* Try it as a function call on the whole row */
                    node = transformWholeRowRef(pstate, rte, cref->location);
                    node = ParseFuncOrColumn(pstate,
                                             list_make1(makeString(colname)),
                                             list_make1(node),
                                             NIL, false, false, false,
                                             NULL, true, cref->location);
                }
                break;
            }
        case 4:
            {
                Node       *field1 = (Node *) linitial(cref->fields);
                Node       *field2 = (Node *) lsecond(cref->fields);
                Node       *field3 = (Node *) lthird(cref->fields);
                Node       *field4 = (Node *) lfourth(cref->fields);
                char       *catname;

                Assert(IsA(field1, String));
                catname = strVal(field1);
                Assert(IsA(field2, String));
                nspname = strVal(field2);
                Assert(IsA(field3, String));
                relname = strVal(field3);

                /*
                 * We check the catalog name and then ignore it.
                 */
                if (strcmp(catname, get_database_name(MyDatabaseId)) != 0)
                {
                    crerr = CRERR_WRONG_DB;
                    break;
                }

                /* Locate the referenced RTE */
                rte = refnameRangeTblEntry(pstate, nspname, relname,
                                           cref->location,
                                           &levels_up);
                if (rte == NULL)
                {
                    crerr = CRERR_NO_RTE;
                    break;
                }

                /* Whole-row reference? */
                if (IsA(field4, A_Star))
                {
                    node = transformWholeRowRef(pstate, rte, cref->location);
                    break;
                }

                Assert(IsA(field4, String));
                colname = strVal(field4);

                /* Try to identify as a column of the RTE */
                node = scanRTEForColumn(pstate, rte, colname, cref->location);
                if (node == NULL)
                {
                    /* Try it as a function call on the whole row */
                    node = transformWholeRowRef(pstate, rte, cref->location);
                    node = ParseFuncOrColumn(pstate,
                                             list_make1(makeString(colname)),
                                             list_make1(node),
                                             NIL, false, false, false,
                                             NULL, true, cref->location);
                }
                break;
            }
        default:
            crerr = CRERR_TOO_MANY;     /* too many dotted names */
            break;
    }

    /*
     * Now give the PostParseColumnRefHook, if any, a chance.  We pass the
     * translation-so-far so that it can throw an error if it wishes in the
     * case that it has a conflicting interpretation of the ColumnRef. (If it
     * just translates anyway, we'll throw an error, because we can't undo
     * whatever effects the preceding steps may have had on the pstate.) If it
     * returns NULL, use the standard translation, or throw a suitable error
     * if there is none.
     */
    if (pstate->p_post_columnref_hook != NULL)
    {
        Node       *hookresult;

        hookresult = (*pstate->p_post_columnref_hook) (pstate, cref, node);
        if (node == NULL)
            node = hookresult;
        else if (hookresult != NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_AMBIGUOUS_COLUMN),
                     errmsg("column reference \"%s\" is ambiguous",
                            NameListToString(cref->fields)),
                     parser_errposition(pstate, cref->location)));
    }

    /*
     * Throw error if no translation found.
     */
    if (node == NULL)
    {
        switch (crerr)
        {
            case CRERR_NO_COLUMN:
                errorMissingColumn(pstate, relname, colname, cref->location);
                break;
            case CRERR_NO_RTE:
                errorMissingRTE(pstate, makeRangeVar(nspname, relname,
                                                     cref->location));
                break;
            case CRERR_WRONG_DB:
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                  errmsg("cross-database references are not implemented: %s",
                         NameListToString(cref->fields)),
                         parser_errposition(pstate, cref->location)));
                break;
            case CRERR_TOO_MANY:
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                errmsg("improper qualified name (too many dotted names): %s",
                       NameListToString(cref->fields)),
                         parser_errposition(pstate, cref->location)));
                break;
        }
    }

    return node;
}

static Node *
transformParamRef(ParseState *pstate, ParamRef *pref)
{
    Node       *result;

    /*
     * The core parser knows nothing about Params.  If a hook is supplied,
     * call it.  If not, or if the hook returns NULL, throw a generic error.
     */
    if (pstate->p_paramref_hook != NULL)
        result = (*pstate->p_paramref_hook) (pstate, pref);
    else
        result = NULL;

    if (result == NULL)
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_PARAMETER),
                 errmsg("there is no parameter $%d", pref->number),
                 parser_errposition(pstate, pref->location)));

    return result;
}

/* Test whether an a_expr is a plain NULL constant or not */
static bool
exprIsNullConstant(Node *arg)
{
    if (arg && IsA(arg, A_Const))
    {
        A_Const    *con = (A_Const *) arg;

        if (con->val.type == T_Null)
            return true;
    }
    return false;
}

static Node *
transformAExprOp(ParseState *pstate, A_Expr *a)
{
    Node       *lexpr = a->lexpr;
    Node       *rexpr = a->rexpr;
    Node       *result;

    /*
     * Special-case "foo = NULL" and "NULL = foo" for compatibility with
     * standards-broken products (like Microsoft's).  Turn these into IS NULL
     * exprs. (If either side is a CaseTestExpr, then the expression was
     * generated internally from a CASE-WHEN expression, and
     * transform_null_equals does not apply.)
     */
    if (Transform_null_equals &&
        list_length(a->name) == 1 &&
        strcmp(strVal(linitial(a->name)), "=") == 0 &&
        (exprIsNullConstant(lexpr) || exprIsNullConstant(rexpr)) &&
        (!IsA(lexpr, CaseTestExpr) &&!IsA(rexpr, CaseTestExpr)))
    {
        NullTest   *n = makeNode(NullTest);

        n->nulltesttype = IS_NULL;

        if (exprIsNullConstant(lexpr))
            n->arg = (Expr *) rexpr;
        else
            n->arg = (Expr *) lexpr;

        result = transformExprRecurse(pstate, (Node *) n);
    }
    else if (lexpr && IsA(lexpr, RowExpr) &&
             rexpr && IsA(rexpr, SubLink) &&
             ((SubLink *) rexpr)->subLinkType == EXPR_SUBLINK)
    {
        /*
         * Convert "row op subselect" into a ROWCOMPARE sublink. Formerly the
         * grammar did this, but now that a row construct is allowed anywhere
         * in expressions, it's easier to do it here.
         */
        SubLink    *s = (SubLink *) rexpr;

        s->subLinkType = ROWCOMPARE_SUBLINK;
        s->testexpr = lexpr;
        s->operName = a->name;
        s->location = a->location;
        result = transformExprRecurse(pstate, (Node *) s);
    }
    else if (lexpr && IsA(lexpr, RowExpr) &&
             rexpr && IsA(rexpr, RowExpr))
    {
        /* "row op row" */
        lexpr = transformExprRecurse(pstate, lexpr);
        rexpr = transformExprRecurse(pstate, rexpr);
        Assert(IsA(lexpr, RowExpr));
        Assert(IsA(rexpr, RowExpr));

        result = make_row_comparison_op(pstate,
                                        a->name,
                                        ((RowExpr *) lexpr)->args,
                                        ((RowExpr *) rexpr)->args,
                                        a->location);
    }
    else
    {
        /* Ordinary scalar operator */
        lexpr = transformExprRecurse(pstate, lexpr);
        rexpr = transformExprRecurse(pstate, rexpr);

        result = (Node *) make_op(pstate,
                                  a->name,
                                  lexpr,
                                  rexpr,
                                  a->location);
    }

    return result;
}

static Node *
transformAExprAnd(ParseState *pstate, A_Expr *a)
{
    Node       *lexpr = transformExprRecurse(pstate, a->lexpr);
    Node       *rexpr = transformExprRecurse(pstate, a->rexpr);

    lexpr = coerce_to_boolean(pstate, lexpr, "AND");
    rexpr = coerce_to_boolean(pstate, rexpr, "AND");

    return (Node *) makeBoolExpr(AND_EXPR,
                                 list_make2(lexpr, rexpr),
                                 a->location);
}

static Node *
transformAExprOr(ParseState *pstate, A_Expr *a)
{
    Node       *lexpr = transformExprRecurse(pstate, a->lexpr);
    Node       *rexpr = transformExprRecurse(pstate, a->rexpr);

    lexpr = coerce_to_boolean(pstate, lexpr, "OR");
    rexpr = coerce_to_boolean(pstate, rexpr, "OR");

    return (Node *) makeBoolExpr(OR_EXPR,
                                 list_make2(lexpr, rexpr),
                                 a->location);
}

static Node *
transformAExprNot(ParseState *pstate, A_Expr *a)
{
    Node       *rexpr = transformExprRecurse(pstate, a->rexpr);

    rexpr = coerce_to_boolean(pstate, rexpr, "NOT");

    return (Node *) makeBoolExpr(NOT_EXPR,
                                 list_make1(rexpr),
                                 a->location);
}

static Node *
transformAExprOpAny(ParseState *pstate, A_Expr *a)
{
    Node       *lexpr = transformExprRecurse(pstate, a->lexpr);
    Node       *rexpr = transformExprRecurse(pstate, a->rexpr);

    return (Node *) make_scalar_array_op(pstate,
                                         a->name,
                                         true,
                                         lexpr,
                                         rexpr,
                                         a->location);
}

static Node *
transformAExprOpAll(ParseState *pstate, A_Expr *a)
{
    Node       *lexpr = transformExprRecurse(pstate, a->lexpr);
    Node       *rexpr = transformExprRecurse(pstate, a->rexpr);

    return (Node *) make_scalar_array_op(pstate,
                                         a->name,
                                         false,
                                         lexpr,
                                         rexpr,
                                         a->location);
}

static Node *
transformAExprDistinct(ParseState *pstate, A_Expr *a)
{
    Node       *lexpr = transformExprRecurse(pstate, a->lexpr);
    Node       *rexpr = transformExprRecurse(pstate, a->rexpr);

    if (lexpr && IsA(lexpr, RowExpr) &&
        rexpr && IsA(rexpr, RowExpr))
    {
        /* "row op row" */
        return make_row_distinct_op(pstate, a->name,
                                    (RowExpr *) lexpr,
                                    (RowExpr *) rexpr,
                                    a->location);
    }
    else
    {
        /* Ordinary scalar operator */
        return (Node *) make_distinct_op(pstate,
                                         a->name,
                                         lexpr,
                                         rexpr,
                                         a->location);
    }
}

static Node *
transformAExprNullIf(ParseState *pstate, A_Expr *a)
{
    Node       *lexpr = transformExprRecurse(pstate, a->lexpr);
    Node       *rexpr = transformExprRecurse(pstate, a->rexpr);
    OpExpr     *result;

    result = (OpExpr *) make_op(pstate,
                                a->name,
                                lexpr,
                                rexpr,
                                a->location);

    /*
     * The comparison operator itself should yield boolean ...
     */
    if (result->opresulttype != BOOLOID)
        ereport(ERROR,
                (errcode(ERRCODE_DATATYPE_MISMATCH),
                 errmsg("NULLIF requires = operator to yield boolean"),
                 parser_errposition(pstate, a->location)));

    /*
     * ... but the NullIfExpr will yield the first operand's type.
     */
    result->opresulttype = exprType((Node *) linitial(result->args));

    /*
     * We rely on NullIfExpr and OpExpr being the same struct
     */
    NodeSetTag(result, T_NullIfExpr);

    return (Node *) result;
}

static Node *
transformAExprOf(ParseState *pstate, A_Expr *a)
{
    /*
     * Checking an expression for match to a list of type names. Will result
     * in a boolean constant node.
     */
    Node       *lexpr = transformExprRecurse(pstate, a->lexpr);
    Const      *result;
    ListCell   *telem;
    Oid         ltype,
                rtype;
    bool        matched = false;

    ltype = exprType(lexpr);
    foreach(telem, (List *) a->rexpr)
    {
        rtype = typenameTypeId(pstate, lfirst(telem));
        matched = (rtype == ltype);
        if (matched)
            break;
    }

    /*
     * We have two forms: equals or not equals. Flip the sense of the result
     * for not equals.
     */
    if (strcmp(strVal(linitial(a->name)), "<>") == 0)
        matched = (!matched);

    result = (Const *) makeBoolConst(matched, false);

    /* Make the result have the original input's parse location */
    result->location = exprLocation((Node *) a);

    return (Node *) result;
}

static Node *
transformAExprIn(ParseState *pstate, A_Expr *a)
{
    Node       *result = NULL;
    Node       *lexpr;
    List       *rexprs;
    List       *rvars;
    List       *rnonvars;
    bool        useOr;
    bool        haveRowExpr;
    ListCell   *l;

    /*
     * If the operator is <>, combine with AND not OR.
     */
    if (strcmp(strVal(linitial(a->name)), "<>") == 0)
        useOr = false;
    else
        useOr = true;

    /*
     * We try to generate a ScalarArrayOpExpr from IN/NOT IN, but this is only
     * possible if the inputs are all scalars (no RowExprs) and there is a
     * suitable array type available.  If not, we fall back to a boolean
     * condition tree with multiple copies of the lefthand expression. Also,
     * any IN-list items that contain Vars are handled as separate boolean
     * conditions, because that gives the planner more scope for optimization
     * on such clauses.
     *
     * First step: transform all the inputs, and detect whether any are
     * RowExprs or contain Vars.
     */
    lexpr = transformExprRecurse(pstate, a->lexpr);
    haveRowExpr = (lexpr && IsA(lexpr, RowExpr));
    rexprs = rvars = rnonvars = NIL;
    foreach(l, (List *) a->rexpr)
    {
        Node       *rexpr = transformExprRecurse(pstate, lfirst(l));

        haveRowExpr |= (rexpr && IsA(rexpr, RowExpr));
        rexprs = lappend(rexprs, rexpr);
        if (contain_vars_of_level(rexpr, 0))
            rvars = lappend(rvars, rexpr);
        else
            rnonvars = lappend(rnonvars, rexpr);
    }

    /*
     * ScalarArrayOpExpr is only going to be useful if there's more than one
     * non-Var righthand item.  Also, it won't work for RowExprs.
     */
    if (!haveRowExpr && list_length(rnonvars) > 1)
    {
        List       *allexprs;
        Oid         scalar_type;
        Oid         array_type;

        /*
         * Try to select a common type for the array elements.  Note that
         * since the LHS' type is first in the list, it will be preferred when
         * there is doubt (eg, when all the RHS items are unknown literals).
         *
         * Note: use list_concat here not lcons, to avoid damaging rnonvars.
         */
        allexprs = list_concat(list_make1(lexpr), rnonvars);
        scalar_type = select_common_type(pstate, allexprs, NULL, NULL);

        /* Do we have an array type to use? */
        if (OidIsValid(scalar_type))
            array_type = get_array_type(scalar_type);
        else
            array_type = InvalidOid;
        if (array_type != InvalidOid)
        {
            /*
             * OK: coerce all the right-hand non-Var inputs to the common type
             * and build an ArrayExpr for them.
             */
            List       *aexprs;
            ArrayExpr  *newa;

            aexprs = NIL;
            foreach(l, rnonvars)
            {
                Node       *rexpr = (Node *) lfirst(l);

                rexpr = coerce_to_common_type(pstate, rexpr,
                                              scalar_type,
                                              "IN");
                aexprs = lappend(aexprs, rexpr);
            }
            newa = makeNode(ArrayExpr);
            newa->array_typeid = array_type;
            /* array_collid will be set by parse_collate.c */
            newa->element_typeid = scalar_type;
            newa->elements = aexprs;
            newa->multidims = false;
            newa->location = -1;

            result = (Node *) make_scalar_array_op(pstate,
                                                   a->name,
                                                   useOr,
                                                   lexpr,
                                                   (Node *) newa,
                                                   a->location);

            /* Consider only the Vars (if any) in the loop below */
            rexprs = rvars;
        }
    }

    /*
     * Must do it the hard way, ie, with a boolean expression tree.
     */
    foreach(l, rexprs)
    {
        Node       *rexpr = (Node *) lfirst(l);
        Node       *cmp;

        if (haveRowExpr)
        {
            if (!IsA(lexpr, RowExpr) ||
                !IsA(rexpr, RowExpr))
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                   errmsg("arguments of row IN must all be row expressions"),
                         parser_errposition(pstate, a->location)));
            cmp = make_row_comparison_op(pstate,
                                         a->name,
                              (List *) copyObject(((RowExpr *) lexpr)->args),
                                         ((RowExpr *) rexpr)->args,
                                         a->location);
        }
        else
            cmp = (Node *) make_op(pstate,
                                   a->name,
                                   copyObject(lexpr),
                                   rexpr,
                                   a->location);

        cmp = coerce_to_boolean(pstate, cmp, "IN");
        if (result == NULL)
            result = cmp;
        else
            result = (Node *) makeBoolExpr(useOr ? OR_EXPR : AND_EXPR,
                                           list_make2(result, cmp),
                                           a->location);
    }

    return result;
}

static Node *
transformFuncCall(ParseState *pstate, FuncCall *fn)
{
    List       *targs;
    ListCell   *args;

    /* Transform the list of arguments ... */
    targs = NIL;
    foreach(args, fn->args)
    {
        targs = lappend(targs, transformExprRecurse(pstate,
                                                    (Node *) lfirst(args)));
    }

    /* ... and hand off to ParseFuncOrColumn */
    return ParseFuncOrColumn(pstate,
                             fn->funcname,
                             targs,
                             fn->agg_order,
                             fn->agg_star,
                             fn->agg_distinct,
                             fn->func_variadic,
                             fn->over,
                             false,
                             fn->location);
}

static Node *
transformCaseExpr(ParseState *pstate, CaseExpr *c)
{
    CaseExpr   *newc;
    Node       *arg;
    CaseTestExpr *placeholder;
    List       *newargs;
    List       *resultexprs;
    ListCell   *l;
    Node       *defresult;
    Oid         ptype;

    /* If we already transformed this node, do nothing */
    if (OidIsValid(c->casetype))
        return (Node *) c;

    newc = makeNode(CaseExpr);

    /* transform the test expression, if any */
    arg = transformExprRecurse(pstate, (Node *) c->arg);

    /* generate placeholder for test expression */
    if (arg)
    {
        /*
         * If test expression is an untyped literal, force it to text. We have
         * to do something now because we won't be able to do this coercion on
         * the placeholder.  This is not as flexible as what was done in 7.4
         * and before, but it's good enough to handle the sort of silly coding
         * commonly seen.
         */
        if (exprType(arg) == UNKNOWNOID)
            arg = coerce_to_common_type(pstate, arg, TEXTOID, "CASE");

        /*
         * Run collation assignment on the test expression so that we know
         * what collation to mark the placeholder with.  In principle we could
         * leave it to parse_collate.c to do that later, but propagating the
         * result to the CaseTestExpr would be unnecessarily complicated.
         */
        assign_expr_collations(pstate, arg);

        placeholder = makeNode(CaseTestExpr);
        placeholder->typeId = exprType(arg);
        placeholder->typeMod = exprTypmod(arg);
        placeholder->collation = exprCollation(arg);
    }
    else
        placeholder = NULL;

    newc->arg = (Expr *) arg;

    /* transform the list of arguments */
    newargs = NIL;
    resultexprs = NIL;
    foreach(l, c->args)
    {
        CaseWhen   *w = (CaseWhen *) lfirst(l);
        CaseWhen   *neww = makeNode(CaseWhen);
        Node       *warg;

        Assert(IsA(w, CaseWhen));

        warg = (Node *) w->expr;
        if (placeholder)
        {
            /* shorthand form was specified, so expand... */
            warg = (Node *) makeSimpleA_Expr(AEXPR_OP, "=",
                                             (Node *) placeholder,
                                             warg,
                                             w->location);
        }
        neww->expr = (Expr *) transformExprRecurse(pstate, warg);

        neww->expr = (Expr *) coerce_to_boolean(pstate,
                                                (Node *) neww->expr,
                                                "CASE/WHEN");

        warg = (Node *) w->result;
        neww->result = (Expr *) transformExprRecurse(pstate, warg);
        neww->location = w->location;

        newargs = lappend(newargs, neww);
        resultexprs = lappend(resultexprs, neww->result);
    }

    newc->args = newargs;

    /* transform the default clause */
    defresult = (Node *) c->defresult;
    if (defresult == NULL)
    {
        A_Const    *n = makeNode(A_Const);

        n->val.type = T_Null;
        n->location = -1;
        defresult = (Node *) n;
    }
    newc->defresult = (Expr *) transformExprRecurse(pstate, defresult);

    /*
     * Note: default result is considered the most significant type in
     * determining preferred type. This is how the code worked before, but it
     * seems a little bogus to me --- tgl
     */
    resultexprs = lcons(newc->defresult, resultexprs);

    ptype = select_common_type(pstate, resultexprs, "CASE", NULL);
    Assert(OidIsValid(ptype));
    newc->casetype = ptype;
    /* casecollid will be set by parse_collate.c */

    /* Convert default result clause, if necessary */
    newc->defresult = (Expr *)
        coerce_to_common_type(pstate,
                              (Node *) newc->defresult,
                              ptype,
                              "CASE/ELSE");

    /* Convert when-clause results, if necessary */
    foreach(l, newc->args)
    {
        CaseWhen   *w = (CaseWhen *) lfirst(l);

        w->result = (Expr *)
            coerce_to_common_type(pstate,
                                  (Node *) w->result,
                                  ptype,
                                  "CASE/WHEN");
    }

    newc->location = c->location;

    return (Node *) newc;
}

static Node *
transformSubLink(ParseState *pstate, SubLink *sublink)
{
    Node       *result = (Node *) sublink;
    Query      *qtree;
    const char *err;

    /* If we already transformed this node, do nothing */
    if (IsA(sublink->subselect, Query))
        return result;

    /*
     * Check to see if the sublink is in an invalid place within the query.
     * We allow sublinks everywhere in SELECT/INSERT/UPDATE/DELETE, but
     * generally not in utility statements.
     */
    err = NULL;
    switch (pstate->p_expr_kind)
    {
        case EXPR_KIND_NONE:
            Assert(false);      /* can't happen */
            break;
        case EXPR_KIND_OTHER:
            /* Accept sublink here; caller must throw error if wanted */
            break;
        case EXPR_KIND_JOIN_ON:
        case EXPR_KIND_JOIN_USING:
        case EXPR_KIND_FROM_SUBSELECT:
        case EXPR_KIND_FROM_FUNCTION:
        case EXPR_KIND_WHERE:
        case EXPR_KIND_HAVING:
        case EXPR_KIND_WINDOW_PARTITION:
        case EXPR_KIND_WINDOW_ORDER:
        case EXPR_KIND_WINDOW_FRAME_RANGE:
        case EXPR_KIND_WINDOW_FRAME_ROWS:
        case EXPR_KIND_SELECT_TARGET:
        case EXPR_KIND_INSERT_TARGET:
        case EXPR_KIND_UPDATE_SOURCE:
        case EXPR_KIND_UPDATE_TARGET:
        case EXPR_KIND_GROUP_BY:
        case EXPR_KIND_ORDER_BY:
        case EXPR_KIND_DISTINCT_ON:
        case EXPR_KIND_LIMIT:
        case EXPR_KIND_OFFSET:
        case EXPR_KIND_RETURNING:
        case EXPR_KIND_VALUES:
            /* okay */
            break;
        case EXPR_KIND_CHECK_CONSTRAINT:
        case EXPR_KIND_DOMAIN_CHECK:
            err = _("cannot use subquery in check constraint");
            break;
        case EXPR_KIND_COLUMN_DEFAULT:
        case EXPR_KIND_FUNCTION_DEFAULT:
            err = _("cannot use subquery in DEFAULT expression");
            break;
        case EXPR_KIND_INDEX_EXPRESSION:
            err = _("cannot use subquery in index expression");
            break;
        case EXPR_KIND_INDEX_PREDICATE:
            err = _("cannot use subquery in index predicate");
            break;
        case EXPR_KIND_ALTER_COL_TRANSFORM:
            err = _("cannot use subquery in transform expression");
            break;
        case EXPR_KIND_EXECUTE_PARAMETER:
            err = _("cannot use subquery in EXECUTE parameter");
            break;
        case EXPR_KIND_TRIGGER_WHEN:
            err = _("cannot use subquery in trigger WHEN condition");
            break;

            /*
             * There is intentionally no default: case here, so that the
             * compiler will warn if we add a new ParseExprKind without
             * extending this switch.  If we do see an unrecognized value at
             * runtime, the behavior will be the same as for EXPR_KIND_OTHER,
             * which is sane anyway.
             */
    }
    if (err)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg_internal("%s", err),
                 parser_errposition(pstate, sublink->location)));

    pstate->p_hasSubLinks = true;

    /*
     * OK, let's transform the sub-SELECT.
     */
    qtree = parse_sub_analyze(sublink->subselect, pstate, NULL, false);

    /*
     * Check that we got something reasonable.  Many of these conditions are
     * impossible given restrictions of the grammar, but check 'em anyway.
     */
    if (!IsA(qtree, Query) ||
        qtree->commandType != CMD_SELECT ||
        qtree->utilityStmt != NULL)
        elog(ERROR, "unexpected non-SELECT command in SubLink");

    sublink->subselect = (Node *) qtree;

    if (sublink->subLinkType == EXISTS_SUBLINK)
    {
        /*
         * EXISTS needs no test expression or combining operator. These fields
         * should be null already, but make sure.
         */
        sublink->testexpr = NULL;
        sublink->operName = NIL;
    }
    else if (sublink->subLinkType == EXPR_SUBLINK ||
             sublink->subLinkType == ARRAY_SUBLINK)
    {
        ListCell   *tlist_item = list_head(qtree->targetList);

        /*
         * Make sure the subselect delivers a single column (ignoring resjunk
         * targets).
         */
        if (tlist_item == NULL ||
            ((TargetEntry *) lfirst(tlist_item))->resjunk)
            ereport(ERROR,
                    (errcode(ERRCODE_SYNTAX_ERROR),
                     errmsg("subquery must return a column"),
                     parser_errposition(pstate, sublink->location)));
        while ((tlist_item = lnext(tlist_item)) != NULL)
        {
            if (!((TargetEntry *) lfirst(tlist_item))->resjunk)
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("subquery must return only one column"),
                         parser_errposition(pstate, sublink->location)));
        }

        /*
         * EXPR and ARRAY need no test expression or combining operator. These
         * fields should be null already, but make sure.
         */
        sublink->testexpr = NULL;
        sublink->operName = NIL;
    }
    else
    {
        /* ALL, ANY, or ROWCOMPARE: generate row-comparing expression */
        Node       *lefthand;
        List       *left_list;
        List       *right_list;
        ListCell   *l;

        /*
         * Transform lefthand expression, and convert to a list
         */
        lefthand = transformExprRecurse(pstate, sublink->testexpr);
        if (lefthand && IsA(lefthand, RowExpr))
            left_list = ((RowExpr *) lefthand)->args;
        else
            left_list = list_make1(lefthand);

        /*
         * Build a list of PARAM_SUBLINK nodes representing the output columns
         * of the subquery.
         */
        right_list = NIL;
        foreach(l, qtree->targetList)
        {
            TargetEntry *tent = (TargetEntry *) lfirst(l);
            Param      *param;

            if (tent->resjunk)
                continue;

            param = makeNode(Param);
            param->paramkind = PARAM_SUBLINK;
            param->paramid = tent->resno;
            param->paramtype = exprType((Node *) tent->expr);
            param->paramtypmod = exprTypmod((Node *) tent->expr);
            param->paramcollid = exprCollation((Node *) tent->expr);
            param->location = -1;

            right_list = lappend(right_list, param);
        }

        /*
         * We could rely on make_row_comparison_op to complain if the list
         * lengths differ, but we prefer to generate a more specific error
         * message.
         */
        if (list_length(left_list) < list_length(right_list))
            ereport(ERROR,
                    (errcode(ERRCODE_SYNTAX_ERROR),
                     errmsg("subquery has too many columns"),
                     parser_errposition(pstate, sublink->location)));
        if (list_length(left_list) > list_length(right_list))
            ereport(ERROR,
                    (errcode(ERRCODE_SYNTAX_ERROR),
                     errmsg("subquery has too few columns"),
                     parser_errposition(pstate, sublink->location)));

        /*
         * Identify the combining operator(s) and generate a suitable
         * row-comparison expression.
         */
        sublink->testexpr = make_row_comparison_op(pstate,
                                                   sublink->operName,
                                                   left_list,
                                                   right_list,
                                                   sublink->location);
    }

    return result;
}

/*
 * transformArrayExpr
 *
 * If the caller specifies the target type, the resulting array will
 * be of exactly that type.  Otherwise we try to infer a common type
 * for the elements using select_common_type().
 */
static Node *
transformArrayExpr(ParseState *pstate, A_ArrayExpr *a,
                   Oid array_type, Oid element_type, int32 typmod)
{
    ArrayExpr  *newa = makeNode(ArrayExpr);
    List       *newelems = NIL;
    List       *newcoercedelems = NIL;
    ListCell   *element;
    Oid         coerce_type;
    bool        coerce_hard;

    /*
     * Transform the element expressions
     *
     * Assume that the array is one-dimensional unless we find an array-type
     * element expression.
     */
    newa->multidims = false;
    foreach(element, a->elements)
    {
        Node       *e = (Node *) lfirst(element);
        Node       *newe;

        /*
         * If an element is itself an A_ArrayExpr, recurse directly so that we
         * can pass down any target type we were given.
         */
        if (IsA(e, A_ArrayExpr))
        {
            newe = transformArrayExpr(pstate,
                                      (A_ArrayExpr *) e,
                                      array_type,
                                      element_type,
                                      typmod);
            /* we certainly have an array here */
            Assert(array_type == InvalidOid || array_type == exprType(newe));
            newa->multidims = true;
        }
        else
        {
            newe = transformExprRecurse(pstate, e);

            /*
             * Check for sub-array expressions, if we haven't already found
             * one.
             */
            if (!newa->multidims && type_is_array(exprType(newe)))
                newa->multidims = true;
        }

        newelems = lappend(newelems, newe);
    }

    /*
     * Select a target type for the elements.
     *
     * If we haven't been given a target array type, we must try to deduce a
     * common type based on the types of the individual elements present.
     */
    if (OidIsValid(array_type))
    {
        /* Caller must ensure array_type matches element_type */
        Assert(OidIsValid(element_type));
        coerce_type = (newa->multidims ? array_type : element_type);
        coerce_hard = true;
    }
    else
    {
        /* Can't handle an empty array without a target type */
        if (newelems == NIL)
            ereport(ERROR,
                    (errcode(ERRCODE_INDETERMINATE_DATATYPE),
                     errmsg("cannot determine type of empty array"),
                     errhint("Explicitly cast to the desired type, "
                             "for example ARRAY[]::integer[]."),
                     parser_errposition(pstate, a->location)));

        /* Select a common type for the elements */
        coerce_type = select_common_type(pstate, newelems, "ARRAY", NULL);

        if (newa->multidims)
        {
            array_type = coerce_type;
            element_type = get_element_type(array_type);
            if (!OidIsValid(element_type))
                ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_OBJECT),
                       errmsg("could not find element type for data type %s",
                              format_type_be(array_type)),
                         parser_errposition(pstate, a->location)));
        }
        else
        {
            element_type = coerce_type;
            array_type = get_array_type(element_type);
            if (!OidIsValid(array_type))
                ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_OBJECT),
                         errmsg("could not find array type for data type %s",
                                format_type_be(element_type)),
                         parser_errposition(pstate, a->location)));
        }
        coerce_hard = false;
    }

    /*
     * Coerce elements to target type
     *
     * If the array has been explicitly cast, then the elements are in turn
     * explicitly coerced.
     *
     * If the array's type was merely derived from the common type of its
     * elements, then the elements are implicitly coerced to the common type.
     * This is consistent with other uses of select_common_type().
     */
    foreach(element, newelems)
    {
        Node       *e = (Node *) lfirst(element);
        Node       *newe;

        if (coerce_hard)
        {
            newe = coerce_to_target_type(pstate, e,
                                         exprType(e),
                                         coerce_type,
                                         typmod,
                                         COERCION_EXPLICIT,
                                         COERCE_EXPLICIT_CAST,
                                         -1);
            if (newe == NULL)
                ereport(ERROR,
                        (errcode(ERRCODE_CANNOT_COERCE),
                         errmsg("cannot cast type %s to %s",
                                format_type_be(exprType(e)),
                                format_type_be(coerce_type)),
                         parser_errposition(pstate, exprLocation(e))));
        }
        else
            newe = coerce_to_common_type(pstate, e,
                                         coerce_type,
                                         "ARRAY");
        newcoercedelems = lappend(newcoercedelems, newe);
    }

    newa->array_typeid = array_type;
    /* array_collid will be set by parse_collate.c */
    newa->element_typeid = element_type;
    newa->elements = newcoercedelems;
    newa->location = a->location;

    return (Node *) newa;
}

static Node *
transformRowExpr(ParseState *pstate, RowExpr *r)
{
    RowExpr    *newr;
    char        fname[16];
    int         fnum;
    ListCell   *lc;

    /* If we already transformed this node, do nothing */
    if (OidIsValid(r->row_typeid))
        return (Node *) r;

    newr = makeNode(RowExpr);

    /* Transform the field expressions */
    newr->args = transformExpressionList(pstate, r->args, pstate->p_expr_kind);

    /* Barring later casting, we consider the type RECORD */
    newr->row_typeid = RECORDOID;
    newr->row_format = COERCE_IMPLICIT_CAST;

    /* ROW() has anonymous columns, so invent some field names */
    newr->colnames = NIL;
    fnum = 1;
    foreach(lc, newr->args)
    {
        snprintf(fname, sizeof(fname), "f%d", fnum++);
        newr->colnames = lappend(newr->colnames, makeString(pstrdup(fname)));
    }

    newr->location = r->location;

    return (Node *) newr;
}

static Node *
transformCoalesceExpr(ParseState *pstate, CoalesceExpr *c)
{
    CoalesceExpr *newc = makeNode(CoalesceExpr);
    List       *newargs = NIL;
    List       *newcoercedargs = NIL;
    ListCell   *args;

    foreach(args, c->args)
    {
        Node       *e = (Node *) lfirst(args);
        Node       *newe;

        newe = transformExprRecurse(pstate, e);
        newargs = lappend(newargs, newe);
    }

    newc->coalescetype = select_common_type(pstate, newargs, "COALESCE", NULL);
    /* coalescecollid will be set by parse_collate.c */

    /* Convert arguments if necessary */
    foreach(args, newargs)
    {
        Node       *e = (Node *) lfirst(args);
        Node       *newe;

        newe = coerce_to_common_type(pstate, e,
                                     newc->coalescetype,
                                     "COALESCE");
        newcoercedargs = lappend(newcoercedargs, newe);
    }

    newc->args = newcoercedargs;
    newc->location = c->location;
    return (Node *) newc;
}

static Node *
transformMinMaxExpr(ParseState *pstate, MinMaxExpr *m)
{
    MinMaxExpr *newm = makeNode(MinMaxExpr);
    List       *newargs = NIL;
    List       *newcoercedargs = NIL;
    const char *funcname = (m->op == IS_GREATEST) ? "GREATEST" : "LEAST";
    ListCell   *args;

    newm->op = m->op;
    foreach(args, m->args)
    {
        Node       *e = (Node *) lfirst(args);
        Node       *newe;

        newe = transformExprRecurse(pstate, e);
        newargs = lappend(newargs, newe);
    }

    newm->minmaxtype = select_common_type(pstate, newargs, funcname, NULL);
    /* minmaxcollid and inputcollid will be set by parse_collate.c */

    /* Convert arguments if necessary */
    foreach(args, newargs)
    {
        Node       *e = (Node *) lfirst(args);
        Node       *newe;

        newe = coerce_to_common_type(pstate, e,
                                     newm->minmaxtype,
                                     funcname);
        newcoercedargs = lappend(newcoercedargs, newe);
    }

    newm->args = newcoercedargs;
    newm->location = m->location;
    return (Node *) newm;
}

static Node *
transformXmlExpr(ParseState *pstate, XmlExpr *x)
{
    XmlExpr    *newx;
    ListCell   *lc;
    int         i;

    /* If we already transformed this node, do nothing */
    if (OidIsValid(x->type))
        return (Node *) x;

    newx = makeNode(XmlExpr);
    newx->op = x->op;
    if (x->name)
        newx->name = map_sql_identifier_to_xml_name(x->name, false, false);
    else
        newx->name = NULL;
    newx->xmloption = x->xmloption;
    newx->type = XMLOID;        /* this just marks the node as transformed */
    newx->typmod = -1;
    newx->location = x->location;

    /*
     * gram.y built the named args as a list of ResTarget.  Transform each,
     * and break the names out as a separate list.
     */
    newx->named_args = NIL;
    newx->arg_names = NIL;

    foreach(lc, x->named_args)
    {
        ResTarget  *r = (ResTarget *) lfirst(lc);
        Node       *expr;
        char       *argname;

        Assert(IsA(r, ResTarget));

        expr = transformExprRecurse(pstate, r->val);

        if (r->name)
            argname = map_sql_identifier_to_xml_name(r->name, false, false);
        else if (IsA(r->val, ColumnRef))
            argname = map_sql_identifier_to_xml_name(FigureColname(r->val),
                                                     true, false);
        else
        {
            ereport(ERROR,
                    (errcode(ERRCODE_SYNTAX_ERROR),
                     x->op == IS_XMLELEMENT
            ? errmsg("unnamed XML attribute value must be a column reference")
            : errmsg("unnamed XML element value must be a column reference"),
                     parser_errposition(pstate, r->location)));
            argname = NULL;     /* keep compiler quiet */
        }

        /* reject duplicate argnames in XMLELEMENT only */
        if (x->op == IS_XMLELEMENT)
        {
            ListCell   *lc2;

            foreach(lc2, newx->arg_names)
            {
                if (strcmp(argname, strVal(lfirst(lc2))) == 0)
                    ereport(ERROR,
                            (errcode(ERRCODE_SYNTAX_ERROR),
                    errmsg("XML attribute name \"%s\" appears more than once",
                           argname),
                             parser_errposition(pstate, r->location)));
            }
        }

        newx->named_args = lappend(newx->named_args, expr);
        newx->arg_names = lappend(newx->arg_names, makeString(argname));
    }

    /* The other arguments are of varying types depending on the function */
    newx->args = NIL;
    i = 0;
    foreach(lc, x->args)
    {
        Node       *e = (Node *) lfirst(lc);
        Node       *newe;

        newe = transformExprRecurse(pstate, e);
        switch (x->op)
        {
            case IS_XMLCONCAT:
                newe = coerce_to_specific_type(pstate, newe, XMLOID,
                                               "XMLCONCAT");
                break;
            case IS_XMLELEMENT:
                /* no coercion necessary */
                break;
            case IS_XMLFOREST:
                newe = coerce_to_specific_type(pstate, newe, XMLOID,
                                               "XMLFOREST");
                break;
            case IS_XMLPARSE:
                if (i == 0)
                    newe = coerce_to_specific_type(pstate, newe, TEXTOID,
                                                   "XMLPARSE");
                else
                    newe = coerce_to_boolean(pstate, newe, "XMLPARSE");
                break;
            case IS_XMLPI:
                newe = coerce_to_specific_type(pstate, newe, TEXTOID,
                                               "XMLPI");
                break;
            case IS_XMLROOT:
                if (i == 0)
                    newe = coerce_to_specific_type(pstate, newe, XMLOID,
                                                   "XMLROOT");
                else if (i == 1)
                    newe = coerce_to_specific_type(pstate, newe, TEXTOID,
                                                   "XMLROOT");
                else
                    newe = coerce_to_specific_type(pstate, newe, INT4OID,
                                                   "XMLROOT");
                break;
            case IS_XMLSERIALIZE:
                /* not handled here */
                Assert(false);
                break;
            case IS_DOCUMENT:
                newe = coerce_to_specific_type(pstate, newe, XMLOID,
                                               "IS DOCUMENT");
                break;
        }
        newx->args = lappend(newx->args, newe);
        i++;
    }

    return (Node *) newx;
}

static Node *
transformXmlSerialize(ParseState *pstate, XmlSerialize *xs)
{
    Node       *result;
    XmlExpr    *xexpr;
    Oid         targetType;
    int32       targetTypmod;

    xexpr = makeNode(XmlExpr);
    xexpr->op = IS_XMLSERIALIZE;
    xexpr->args = list_make1(coerce_to_specific_type(pstate,
                                        transformExprRecurse(pstate, xs->expr),
                                                     XMLOID,
                                                     "XMLSERIALIZE"));

    typenameTypeIdAndMod(pstate, xs->typeName, &targetType, &targetTypmod);

    xexpr->xmloption = xs->xmloption;
    xexpr->location = xs->location;
    /* We actually only need these to be able to parse back the expression. */
    xexpr->type = targetType;
    xexpr->typmod = targetTypmod;

    /*
     * The actual target type is determined this way.  SQL allows char and
     * varchar as target types.  We allow anything that can be cast implicitly
     * from text.  This way, user-defined text-like data types automatically
     * fit in.
     */
    result = coerce_to_target_type(pstate, (Node *) xexpr,
                                   TEXTOID, targetType, targetTypmod,
                                   COERCION_IMPLICIT,
                                   COERCE_IMPLICIT_CAST,
                                   -1);
    if (result == NULL)
        ereport(ERROR,
                (errcode(ERRCODE_CANNOT_COERCE),
                 errmsg("cannot cast XMLSERIALIZE result to %s",
                        format_type_be(targetType)),
                 parser_errposition(pstate, xexpr->location)));
    return result;
}

static Node *
transformBooleanTest(ParseState *pstate, BooleanTest *b)
{
    const char *clausename;

    switch (b->booltesttype)
    {
        case IS_TRUE:
            clausename = "IS TRUE";
            break;
        case IS_NOT_TRUE:
            clausename = "IS NOT TRUE";
            break;
        case IS_FALSE:
            clausename = "IS FALSE";
            break;
        case IS_NOT_FALSE:
            clausename = "IS NOT FALSE";
            break;
        case IS_UNKNOWN:
            clausename = "IS UNKNOWN";
            break;
        case IS_NOT_UNKNOWN:
            clausename = "IS NOT UNKNOWN";
            break;
        default:
            elog(ERROR, "unrecognized booltesttype: %d",
                 (int) b->booltesttype);
            clausename = NULL;  /* keep compiler quiet */
    }

    b->arg = (Expr *) transformExprRecurse(pstate, (Node *) b->arg);

    b->arg = (Expr *) coerce_to_boolean(pstate,
                                        (Node *) b->arg,
                                        clausename);

    return (Node *) b;
}

static Node *
transformCurrentOfExpr(ParseState *pstate, CurrentOfExpr *cexpr)
{
    int         sublevels_up;

    /* CURRENT OF can only appear at top level of UPDATE/DELETE */
    Assert(pstate->p_target_rangetblentry != NULL);
    cexpr->cvarno = RTERangeTablePosn(pstate,
                                      pstate->p_target_rangetblentry,
                                      &sublevels_up);
    Assert(sublevels_up == 0);

    /*
     * Check to see if the cursor name matches a parameter of type REFCURSOR.
     * If so, replace the raw name reference with a parameter reference. (This
     * is a hack for the convenience of plpgsql.)
     */
    if (cexpr->cursor_name != NULL)     /* in case already transformed */
    {
        ColumnRef  *cref = makeNode(ColumnRef);
        Node       *node = NULL;

        /* Build an unqualified ColumnRef with the given name */
        cref->fields = list_make1(makeString(cexpr->cursor_name));
        cref->location = -1;

        /* See if there is a translation available from a parser hook */
        if (pstate->p_pre_columnref_hook != NULL)
            node = (*pstate->p_pre_columnref_hook) (pstate, cref);
        if (node == NULL && pstate->p_post_columnref_hook != NULL)
            node = (*pstate->p_post_columnref_hook) (pstate, cref, NULL);

        /*
         * XXX Should we throw an error if we get a translation that isn't a
         * refcursor Param?  For now it seems best to silently ignore false
         * matches.
         */
        if (node != NULL && IsA(node, Param))
        {
            Param      *p = (Param *) node;

            if (p->paramkind == PARAM_EXTERN &&
                p->paramtype == REFCURSOROID)
            {
                /* Matches, so convert CURRENT OF to a param reference */
                cexpr->cursor_name = NULL;
                cexpr->cursor_param = p->paramid;
            }
        }
    }

    return (Node *) cexpr;
}

/*
 * Construct a whole-row reference to represent the notation "relation.*".
 */
static Node *
transformWholeRowRef(ParseState *pstate, RangeTblEntry *rte, int location)
{
    Var        *result;
    int         vnum;
    int         sublevels_up;

    /* Find the RTE's rangetable location */
    vnum = RTERangeTablePosn(pstate, rte, &sublevels_up);

    /*
     * Build the appropriate referencing node.  Note that if the RTE is a
     * function returning scalar, we create just a plain reference to the
     * function value, not a composite containing a single column.  This is
     * pretty inconsistent at first sight, but it's what we've done
     * historically.  One argument for it is that "rel" and "rel.*" mean the
     * same thing for composite relations, so why not for scalar functions...
     */
    result = makeWholeRowVar(rte, vnum, sublevels_up, true);

    /* location is not filled in by makeWholeRowVar */
    result->location = location;

    /* mark relation as requiring whole-row SELECT access */
    markVarForSelectPriv(pstate, result, rte);

    return (Node *) result;
}

/*
 * Handle an explicit CAST construct.
 *
 * Transform the argument, then look up the type name and apply any necessary
 * coercion function(s).
 */
static Node *
transformTypeCast(ParseState *pstate, TypeCast *tc)
{
    Node       *result;
    Node       *expr = transformExprRecurse(pstate, tc->arg);
    Oid         inputType = exprType(expr);
    Oid         targetType;
    int32       targetTypmod;
    int         location;

    typenameTypeIdAndMod(pstate, tc->typeName, &targetType, &targetTypmod);

    if (inputType == InvalidOid)
        return expr;            /* do nothing if NULL input */

    /*
     * Location of the coercion is preferentially the location of the :: or
     * CAST symbol, but if there is none then use the location of the type
     * name (this can happen in TypeName 'string' syntax, for instance).
     */
    location = tc->location;
    if (location < 0)
        location = tc->typeName->location;

    result = coerce_to_target_type(pstate, expr, inputType,
                                   targetType, targetTypmod,
                                   COERCION_EXPLICIT,
                                   COERCE_EXPLICIT_CAST,
                                   location);
    if (result == NULL)
        ereport(ERROR,
                (errcode(ERRCODE_CANNOT_COERCE),
                 errmsg("cannot cast type %s to %s",
                        format_type_be(inputType),
                        format_type_be(targetType)),
                 parser_coercion_errposition(pstate, location, expr)));

    return result;
}

/*
 * Handle an explicit COLLATE clause.
 *
 * Transform the argument, and look up the collation name.
 */
static Node *
transformCollateClause(ParseState *pstate, CollateClause *c)
{
    CollateExpr *newc;
    Oid         argtype;

    newc = makeNode(CollateExpr);
    newc->arg = (Expr *) transformExprRecurse(pstate, c->arg);

    argtype = exprType((Node *) newc->arg);

    /*
     * The unknown type is not collatable, but coerce_type() takes care of it
     * separately, so we'll let it go here.
     */
    if (!type_is_collatable(argtype) && argtype != UNKNOWNOID)
        ereport(ERROR,
                (errcode(ERRCODE_DATATYPE_MISMATCH),
                 errmsg("collations are not supported by type %s",
                        format_type_be(argtype)),
                 parser_errposition(pstate, c->location)));

    newc->collOid = LookupCollation(pstate, c->collname, c->location);
    newc->location = c->location;

    return (Node *) newc;
}

/*
 * Transform a "row compare-op row" construct
 *
 * The inputs are lists of already-transformed expressions.
 * As with coerce_type, pstate may be NULL if no special unknown-Param
 * processing is wanted.
 *
 * The output may be a single OpExpr, an AND or OR combination of OpExprs,
 * or a RowCompareExpr.  In all cases it is guaranteed to return boolean.
 * The AND, OR, and RowCompareExpr cases further imply things about the
 * behavior of the operators (ie, they behave as =, <>, or < <= > >=).
 */
static Node *
make_row_comparison_op(ParseState *pstate, List *opname,
                       List *largs, List *rargs, int location)
{
    RowCompareExpr *rcexpr;
    RowCompareType rctype;
    List       *opexprs;
    List       *opnos;
    List       *opfamilies;
    ListCell   *l,
               *r;
    List      **opinfo_lists;
    Bitmapset  *strats;
    int         nopers;
    int         i;

    nopers = list_length(largs);
    if (nopers != list_length(rargs))
        ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                 errmsg("unequal number of entries in row expressions"),
                 parser_errposition(pstate, location)));

    /*
     * We can't compare zero-length rows because there is no principled basis
     * for figuring out what the operator is.
     */
    if (nopers == 0)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot compare rows of zero length"),
                 parser_errposition(pstate, location)));

    /*
     * Identify all the pairwise operators, using make_op so that behavior is
     * the same as in the simple scalar case.
     */
    opexprs = NIL;
    forboth(l, largs, r, rargs)
    {
        Node       *larg = (Node *) lfirst(l);
        Node       *rarg = (Node *) lfirst(r);
        OpExpr     *cmp;

        cmp = (OpExpr *) make_op(pstate, opname, larg, rarg, location);
        Assert(IsA(cmp, OpExpr));

        /*
         * We don't use coerce_to_boolean here because we insist on the
         * operator yielding boolean directly, not via coercion.  If it
         * doesn't yield bool it won't be in any index opfamilies...
         */
        if (cmp->opresulttype != BOOLOID)
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                   errmsg("row comparison operator must yield type boolean, "
                          "not type %s",
                          format_type_be(cmp->opresulttype)),
                     parser_errposition(pstate, location)));
        if (expression_returns_set((Node *) cmp))
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("row comparison operator must not return a set"),
                     parser_errposition(pstate, location)));
        opexprs = lappend(opexprs, cmp);
    }

    /*
     * If rows are length 1, just return the single operator.  In this case we
     * don't insist on identifying btree semantics for the operator (but we
     * still require it to return boolean).
     */
    if (nopers == 1)
        return (Node *) linitial(opexprs);

    /*
     * Now we must determine which row comparison semantics (= <> < <= > >=)
     * apply to this set of operators.  We look for btree opfamilies
     * containing the operators, and see which interpretations (strategy
     * numbers) exist for each operator.
     */
    opinfo_lists = (List **) palloc(nopers * sizeof(List *));
    strats = NULL;
    i = 0;
    foreach(l, opexprs)
    {
        Oid         opno = ((OpExpr *) lfirst(l))->opno;
        Bitmapset  *this_strats;
        ListCell   *j;

        opinfo_lists[i] = get_op_btree_interpretation(opno);

        /*
         * convert strategy numbers into a Bitmapset to make the intersection
         * calculation easy.
         */
        this_strats = NULL;
        foreach(j, opinfo_lists[i])
        {
            OpBtreeInterpretation *opinfo = lfirst(j);

            this_strats = bms_add_member(this_strats, opinfo->strategy);
        }
        if (i == 0)
            strats = this_strats;
        else
            strats = bms_int_members(strats, this_strats);
        i++;
    }

    /*
     * If there are multiple common interpretations, we may use any one of
     * them ... this coding arbitrarily picks the lowest btree strategy
     * number.
     */
    i = bms_first_member(strats);
    if (i < 0)
    {
        /* No common interpretation, so fail */
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("could not determine interpretation of row comparison operator %s",
                        strVal(llast(opname))),
                 errhint("Row comparison operators must be associated with btree operator families."),
                 parser_errposition(pstate, location)));
    }
    rctype = (RowCompareType) i;

    /*
     * For = and <> cases, we just combine the pairwise operators with AND or
     * OR respectively.
     *
     * Note: this is presently the only place where the parser generates
     * BoolExpr with more than two arguments.  Should be OK since the rest of
     * the system thinks BoolExpr is N-argument anyway.
     */
    if (rctype == ROWCOMPARE_EQ)
        return (Node *) makeBoolExpr(AND_EXPR, opexprs, location);
    if (rctype == ROWCOMPARE_NE)
        return (Node *) makeBoolExpr(OR_EXPR, opexprs, location);

    /*
     * Otherwise we need to choose exactly which opfamily to associate with
     * each operator.
     */
    opfamilies = NIL;
    for (i = 0; i < nopers; i++)
    {
        Oid         opfamily = InvalidOid;
        ListCell   *j;

        foreach(j, opinfo_lists[i])
        {
            OpBtreeInterpretation *opinfo = lfirst(j);

            if (opinfo->strategy == rctype)
            {
                opfamily = opinfo->opfamily_id;
                break;
            }
        }
        if (OidIsValid(opfamily))
            opfamilies = lappend_oid(opfamilies, opfamily);
        else    /* should not happen */
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("could not determine interpretation of row comparison operator %s",
                            strVal(llast(opname))),
               errdetail("There are multiple equally-plausible candidates."),
                     parser_errposition(pstate, location)));
    }

    /*
     * Now deconstruct the OpExprs and create a RowCompareExpr.
     *
     * Note: can't just reuse the passed largs/rargs lists, because of
     * possibility that make_op inserted coercion operations.
     */
    opnos = NIL;
    largs = NIL;
    rargs = NIL;
    foreach(l, opexprs)
    {
        OpExpr     *cmp = (OpExpr *) lfirst(l);

        opnos = lappend_oid(opnos, cmp->opno);
        largs = lappend(largs, linitial(cmp->args));
        rargs = lappend(rargs, lsecond(cmp->args));
    }

    rcexpr = makeNode(RowCompareExpr);
    rcexpr->rctype = rctype;
    rcexpr->opnos = opnos;
    rcexpr->opfamilies = opfamilies;
    rcexpr->inputcollids = NIL; /* assign_expr_collations will fix this */
    rcexpr->largs = largs;
    rcexpr->rargs = rargs;

    return (Node *) rcexpr;
}

/*
 * Transform a "row IS DISTINCT FROM row" construct
 *
 * The input RowExprs are already transformed
 */
static Node *
make_row_distinct_op(ParseState *pstate, List *opname,
                     RowExpr *lrow, RowExpr *rrow,
                     int location)
{
    Node       *result = NULL;
    List       *largs = lrow->args;
    List       *rargs = rrow->args;
    ListCell   *l,
               *r;

    if (list_length(largs) != list_length(rargs))
        ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                 errmsg("unequal number of entries in row expressions"),
                 parser_errposition(pstate, location)));

    forboth(l, largs, r, rargs)
    {
        Node       *larg = (Node *) lfirst(l);
        Node       *rarg = (Node *) lfirst(r);
        Node       *cmp;

        cmp = (Node *) make_distinct_op(pstate, opname, larg, rarg, location);
        if (result == NULL)
            result = cmp;
        else
            result = (Node *) makeBoolExpr(OR_EXPR,
                                           list_make2(result, cmp),
                                           location);
    }

    if (result == NULL)
    {
        /* zero-length rows?  Generate constant FALSE */
        result = makeBoolConst(false, false);
    }

    return result;
}

/*
 * make the node for an IS DISTINCT FROM operator
 */
static Expr *
make_distinct_op(ParseState *pstate, List *opname, Node *ltree, Node *rtree,
                 int location)
{
    Expr       *result;

    result = make_op(pstate, opname, ltree, rtree, location);
    if (((OpExpr *) result)->opresulttype != BOOLOID)
        ereport(ERROR,
                (errcode(ERRCODE_DATATYPE_MISMATCH),
             errmsg("IS DISTINCT FROM requires = operator to yield boolean"),
                 parser_errposition(pstate, location)));

    /*
     * We rely on DistinctExpr and OpExpr being same struct
     */
    NodeSetTag(result, T_DistinctExpr);

    return result;
}

/*
 * Produce a string identifying an expression by kind.
 *
 * Note: when practical, use a simple SQL keyword for the result.  If that
 * doesn't work well, check call sites to see whether custom error message
 * strings are required.
 */
const char *
ParseExprKindName(ParseExprKind exprKind)
{
    switch (exprKind)
    {
        case EXPR_KIND_NONE:
            return "invalid expression context";
        case EXPR_KIND_OTHER:
            return "extension expression";
        case EXPR_KIND_JOIN_ON:
            return "JOIN/ON";
        case EXPR_KIND_JOIN_USING:
            return "JOIN/USING";
        case EXPR_KIND_FROM_SUBSELECT:
            return "sub-SELECT in FROM";
        case EXPR_KIND_FROM_FUNCTION:
            return "function in FROM";
        case EXPR_KIND_WHERE:
            return "WHERE";
        case EXPR_KIND_HAVING:
            return "HAVING";
        case EXPR_KIND_WINDOW_PARTITION:
            return "window PARTITION BY";
        case EXPR_KIND_WINDOW_ORDER:
            return "window ORDER BY";
        case EXPR_KIND_WINDOW_FRAME_RANGE:
            return "window RANGE";
        case EXPR_KIND_WINDOW_FRAME_ROWS:
            return "window ROWS";
        case EXPR_KIND_SELECT_TARGET:
            return "SELECT";
        case EXPR_KIND_INSERT_TARGET:
            return "INSERT";
        case EXPR_KIND_UPDATE_SOURCE:
        case EXPR_KIND_UPDATE_TARGET:
            return "UPDATE";
        case EXPR_KIND_GROUP_BY:
            return "GROUP BY";
        case EXPR_KIND_ORDER_BY:
            return "ORDER BY";
        case EXPR_KIND_DISTINCT_ON:
            return "DISTINCT ON";
        case EXPR_KIND_LIMIT:
            return "LIMIT";
        case EXPR_KIND_OFFSET:
            return "OFFSET";
        case EXPR_KIND_RETURNING:
            return "RETURNING";
        case EXPR_KIND_VALUES:
            return "VALUES";
        case EXPR_KIND_CHECK_CONSTRAINT:
        case EXPR_KIND_DOMAIN_CHECK:
            return "CHECK";
        case EXPR_KIND_COLUMN_DEFAULT:
        case EXPR_KIND_FUNCTION_DEFAULT:
            return "DEFAULT";
        case EXPR_KIND_INDEX_EXPRESSION:
            return "index expression";
        case EXPR_KIND_INDEX_PREDICATE:
            return "index predicate";
        case EXPR_KIND_ALTER_COL_TRANSFORM:
            return "USING";
        case EXPR_KIND_EXECUTE_PARAMETER:
            return "EXECUTE";
        case EXPR_KIND_TRIGGER_WHEN:
            return "WHEN";

            /*
             * There is intentionally no default: case here, so that the
             * compiler will warn if we add a new ParseExprKind without
             * extending this switch.  If we do see an unrecognized value at
             * runtime, we'll fall through to the "unrecognized" return.
             */
    }
    return "unrecognized expression kind";
}