/*-------------------------------------------------------------------------
 *
 * parse_expr.c
 *	  handle expressions in parser
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/parser/parse_expr.c,v 1.186 2005/11/18 23:08:00 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "catalog/pg_operator.h"
#include "catalog/pg_proc.h"
#include "commands/dbcommands.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/params.h"
#include "nodes/plannodes.h"
#include "parser/analyze.h"
#include "parser/gramparse.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "parser/parse_func.h"
#include "parser/parse_oper.h"
#include "parser/parse_relation.h"
#include "parser/parse_type.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"

bool		Transform_null_equals = false;

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 *transformFuncCall(ParseState *pstate, FuncCall *fn);
static Node *transformCaseExpr(ParseState *pstate, CaseExpr *c);
static Node *transformSubLink(ParseState *pstate, SubLink *sublink);
static Node *transformArrayExpr(ParseState *pstate, ArrayExpr *a);
static Node *transformRowExpr(ParseState *pstate, RowExpr *r);
static Node *transformCoalesceExpr(ParseState *pstate, CoalesceExpr *c);
static Node *transformMinMaxExpr(ParseState *pstate, MinMaxExpr *m);
static Node *transformBooleanTest(ParseState *pstate, BooleanTest *b);
static Node *transformColumnRef(ParseState *pstate, ColumnRef *cref);
static Node *transformWholeRowRef(ParseState *pstate, char *schemaname,
					 char *relname);
static Node *transformBooleanTest(ParseState *pstate, BooleanTest *b);
static Node *transformIndirection(ParseState *pstate, Node *basenode,
					 List *indirection);
static Node *typecast_expression(ParseState *pstate, Node *expr,
					TypeName *typename);
static Node *make_row_op(ParseState *pstate, List *opname,
			Node *ltree, Node *rtree);
static Node *make_row_distinct_op(ParseState *pstate, List *opname,
					 Node *ltree, Node *rtree);
static Expr *make_distinct_op(ParseState *pstate, List *opname,
				 Node *ltree, Node *rtree);


/*
 * 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".
 * 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)
{
	Node	   *result = NULL;

	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(val);
				if (con->typename != NULL)
					result = typecast_expression(pstate, result,
												 con->typename);
				break;
			}

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

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

		case T_TypeCast:
			{
				TypeCast   *tc = (TypeCast *) expr;
				Node	   *arg = transformExpr(pstate, tc->arg);

				result = typecast_expression(pstate, arg, tc->typename);
				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;
					default:
						elog(ERROR, "unrecognized A_Expr kind: %d", a->kind);
				}
				break;
			}

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

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

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

		case T_ArrayExpr:
			result = transformArrayExpr(pstate, (ArrayExpr *) 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_NullTest:
			{
				NullTest   *n = (NullTest *) expr;

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

		case T_BooleanTest:
			result = transformBooleanTest(pstate, (BooleanTest *) 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_ArrayRef:
		case T_FuncExpr:
		case T_OpExpr:
		case T_DistinctExpr:
		case T_ScalarArrayOpExpr:
		case T_NullIfExpr:
		case T_BoolExpr:
		case T_FieldSelect:
		case T_FieldStore:
		case T_RelabelType:
		case T_ConvertRowtypeExpr:
		case T_CaseTestExpr:
		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));
			break;
	}

	return result;
}

static Node *
transformIndirection(ParseState *pstate, Node *basenode, List *indirection)
{
	Node	   *result = basenode;
	List	   *subscripts = NIL;
	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
		{
			Assert(IsA(n, String));

			/* process subscripts before this field selection */
			if (subscripts)
				result = (Node *) transformArraySubscripts(pstate,
														   result,
														   exprType(result),
														   InvalidOid,
														   -1,
														   subscripts,
														   NULL);
			subscripts = NIL;

			result = ParseFuncOrColumn(pstate,
									   list_make1(n),
									   list_make1(result),
									   false, false, true);
		}
	}
	/* process trailing subscripts, if any */
	if (subscripts)
		result = (Node *) transformArraySubscripts(pstate,
												   result,
												   exprType(result),
												   InvalidOid,
												   -1,
												   subscripts,
												   NULL);

	return result;
}

static Node *
transformColumnRef(ParseState *pstate, ColumnRef *cref)
{
	int			numnames = list_length(cref->fields);
	Node	   *node;
	int			levels_up;

	/*----------
	 * 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 (numnames)
	{
		case 1:
			{
				char	   *name = strVal(linitial(cref->fields));

				/* Try to identify as an unqualified column */
				node = colNameToVar(pstate, name, false);

				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(name, "value") == 0)
					{
						node = (Node *) copyObject(pstate->p_value_substitute);
						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.*".
					 */
					if (refnameRangeTblEntry(pstate, NULL, name,
											 &levels_up) != NULL)
						node = transformWholeRowRef(pstate, NULL, name);
					else
						ereport(ERROR,
								(errcode(ERRCODE_UNDEFINED_COLUMN),
								 errmsg("column \"%s\" does not exist",
										name)));
				}
				break;
			}
		case 2:
			{
				char	   *name1 = strVal(linitial(cref->fields));
				char	   *name2 = strVal(lsecond(cref->fields));

				/* Whole-row reference? */
				if (strcmp(name2, "*") == 0)
				{
					node = transformWholeRowRef(pstate, NULL, name1);
					break;
				}

				/* Try to identify as a once-qualified column */
				node = qualifiedNameToVar(pstate, NULL, name1, name2, true);
				if (node == NULL)
				{
					/*
					 * Not known as a column of any range-table entry, so try
					 * it as a function call.  Here, we will create an
					 * implicit RTE for tables not already entered.
					 */
					node = transformWholeRowRef(pstate, NULL, name1);
					node = ParseFuncOrColumn(pstate,
											 list_make1(makeString(name2)),
											 list_make1(node),
											 false, false, true);
				}
				break;
			}
		case 3:
			{
				char	   *name1 = strVal(linitial(cref->fields));
				char	   *name2 = strVal(lsecond(cref->fields));
				char	   *name3 = strVal(lthird(cref->fields));

				/* Whole-row reference? */
				if (strcmp(name3, "*") == 0)
				{
					node = transformWholeRowRef(pstate, name1, name2);
					break;
				}

				/* Try to identify as a twice-qualified column */
				node = qualifiedNameToVar(pstate, name1, name2, name3, true);
				if (node == NULL)
				{
					/* Try it as a function call */
					node = transformWholeRowRef(pstate, name1, name2);
					node = ParseFuncOrColumn(pstate,
											 list_make1(makeString(name3)),
											 list_make1(node),
											 false, false, true);
				}
				break;
			}
		case 4:
			{
				char	   *name1 = strVal(linitial(cref->fields));
				char	   *name2 = strVal(lsecond(cref->fields));
				char	   *name3 = strVal(lthird(cref->fields));
				char	   *name4 = strVal(lfourth(cref->fields));

				/*
				 * We check the catalog name and then ignore it.
				 */
				if (strcmp(name1, get_database_name(MyDatabaseId)) != 0)
					ereport(ERROR,
							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
							 errmsg("cross-database references are not implemented: %s",
									NameListToString(cref->fields))));

				/* Whole-row reference? */
				if (strcmp(name4, "*") == 0)
				{
					node = transformWholeRowRef(pstate, name2, name3);
					break;
				}

				/* Try to identify as a twice-qualified column */
				node = qualifiedNameToVar(pstate, name2, name3, name4, true);
				if (node == NULL)
				{
					/* Try it as a function call */
					node = transformWholeRowRef(pstate, name2, name3);
					node = ParseFuncOrColumn(pstate,
											 list_make1(makeString(name4)),
											 list_make1(node),
											 false, false, true);
				}
				break;
			}
		default:
			ereport(ERROR,
					(errcode(ERRCODE_SYNTAX_ERROR),
				errmsg("improper qualified name (too many dotted names): %s",
					   NameListToString(cref->fields))));
			node = NULL;		/* keep compiler quiet */
			break;
	}

	return node;
}

static Node *
transformParamRef(ParseState *pstate, ParamRef *pref)
{
	int			paramno = pref->number;
	ParseState *toppstate;
	Param	   *param;

	/*
	 * Find topmost ParseState, which is where paramtype info lives.
	 */
	toppstate = pstate;
	while (toppstate->parentParseState != NULL)
		toppstate = toppstate->parentParseState;

	/* Check parameter number is in range */
	if (paramno <= 0)			/* probably can't happen? */
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_PARAMETER),
				 errmsg("there is no parameter $%d", paramno)));
	if (paramno > toppstate->p_numparams)
	{
		if (!toppstate->p_variableparams)
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_PARAMETER),
					 errmsg("there is no parameter $%d",
							paramno)));
		/* Okay to enlarge param array */
		if (toppstate->p_paramtypes)
			toppstate->p_paramtypes =
				(Oid *) repalloc(toppstate->p_paramtypes,
								 paramno * sizeof(Oid));
		else
			toppstate->p_paramtypes =
				(Oid *) palloc(paramno * sizeof(Oid));
		/* Zero out the previously-unreferenced slots */
		MemSet(toppstate->p_paramtypes + toppstate->p_numparams,
			   0,
			   (paramno - toppstate->p_numparams) * sizeof(Oid));
		toppstate->p_numparams = paramno;
	}
	if (toppstate->p_variableparams)
	{
		/* If not seen before, initialize to UNKNOWN type */
		if (toppstate->p_paramtypes[paramno - 1] == InvalidOid)
			toppstate->p_paramtypes[paramno - 1] = UNKNOWNOID;
	}

	param = makeNode(Param);
	param->paramkind = PARAM_NUM;
	param->paramid = (AttrNumber) paramno;
	param->paramtype = toppstate->p_paramtypes[paramno - 1];

	return (Node *) param;
}

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 (Transform_null_equals &&
		list_length(a->name) == 1 &&
		strcmp(strVal(linitial(a->name)), "=") == 0 &&
		(exprIsNullConstant(lexpr) || exprIsNullConstant(rexpr)))
	{
		NullTest   *n = makeNode(NullTest);

		n->nulltesttype = IS_NULL;

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

		result = transformExpr(pstate, (Node *) n);
	}
	else if (lexpr && IsA(lexpr, RowExpr) &&
			 rexpr && IsA(rexpr, SubLink) &&
			 ((SubLink *) rexpr)->subLinkType == EXPR_SUBLINK)
	{
		/*
		 * Convert "row op subselect" into a MULTIEXPR 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 = MULTIEXPR_SUBLINK;
		s->lefthand = ((RowExpr *) lexpr)->args;
		s->operName = a->name;
		result = transformExpr(pstate, (Node *) s);
	}
	else if (lexpr && IsA(lexpr, RowExpr) &&
			 rexpr && IsA(rexpr, RowExpr))
	{
		/* "row op row" */
		result = make_row_op(pstate, a->name, lexpr, rexpr);
	}
	else
	{
		/* Ordinary scalar operator */
		lexpr = transformExpr(pstate, lexpr);
		rexpr = transformExpr(pstate, rexpr);

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

	return result;
}

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

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

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

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

	return (Node *) makeBoolExpr(NOT_EXPR,
								 list_make1(rexpr));
}

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

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

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

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

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

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

		return (Node *) make_distinct_op(pstate,
										 a->name,
										 lexpr,
										 rexpr);
	}
}

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

	result = (Node *) make_op(pstate,
							  a->name,
							  lexpr,
							  rexpr);
	if (((OpExpr *) result)->opresulttype != BOOLOID)
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("NULLIF requires = operator to yield boolean")));

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

	return result;
}

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

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

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

	n = makeNode(A_Const);
	n->val.type = T_String;
	n->val.val.str = (matched ? "t" : "f");
	n->typename = SystemTypeName("bool");

	return transformExpr(pstate, (Node *) n);
}

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

	/*
	 * Transform the list of arguments.  We use a shallow list copy and then
	 * transform-in-place to avoid O(N^2) behavior from repeated lappend's.
	 *
	 * XXX: repeated lappend() would no longer result in O(n^2) behavior; worth
	 * reconsidering this design?
	 */
	targs = list_copy(fn->args);
	foreach(args, targs)
	{
		lfirst(args) = transformExpr(pstate,
									 (Node *) lfirst(args));
	}

	return ParseFuncOrColumn(pstate,
							 fn->funcname,
							 targs,
							 fn->agg_star,
							 fn->agg_distinct,
							 false);
}

static Node *
transformCaseExpr(ParseState *pstate, CaseExpr *c)
{
	CaseExpr   *newc;
	Node	   *arg;
	CaseTestExpr *placeholder;
	List	   *newargs;
	List	   *typeids;
	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 = transformExpr(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");

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

	newc->arg = (Expr *) arg;

	/* transform the list of arguments */
	newargs = NIL;
	typeids = 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);
		}
		neww->expr = (Expr *) transformExpr(pstate, warg);

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

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

		newargs = lappend(newargs, neww);
		typeids = lappend_oid(typeids, exprType((Node *) 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;
		defresult = (Node *) n;
	}
	newc->defresult = (Expr *) transformExpr(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
	 */
	typeids = lcons_oid(exprType((Node *) newc->defresult), typeids);

	ptype = select_common_type(typeids, "CASE");
	Assert(OidIsValid(ptype));
	newc->casetype = ptype;

	/* 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");
	}

	return (Node *) newc;
}

static Node *
transformSubLink(ParseState *pstate, SubLink *sublink)
{
	List	   *qtrees;
	Query	   *qtree;
	Node	   *result = (Node *) sublink;

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

	pstate->p_hasSubLinks = true;
	qtrees = parse_sub_analyze(sublink->subselect, pstate);
	if (list_length(qtrees) != 1)
		elog(ERROR, "bad query in sub-select");
	qtree = (Query *) linitial(qtrees);
	if (qtree->commandType != CMD_SELECT ||
		qtree->resultRelation != 0)
		elog(ERROR, "bad query in sub-select");
	sublink->subselect = (Node *) qtree;

	if (sublink->subLinkType == EXISTS_SUBLINK)
	{
		/*
		 * EXISTS needs no lefthand or combining operator.	These fields
		 * should be NIL already, but make sure.
		 */
		sublink->lefthand = NIL;
		sublink->operName = NIL;
		sublink->operOids = NIL;
		sublink->useOr = FALSE;
	}
	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")));
		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")));
		}

		/*
		 * EXPR and ARRAY need no lefthand or combining operator. These fields
		 * should be NIL already, but make sure.
		 */
		sublink->lefthand = NIL;
		sublink->operName = NIL;
		sublink->operOids = NIL;
		sublink->useOr = FALSE;
	}
	else
	{
		/* ALL, ANY, or MULTIEXPR: generate operator list */
		List	   *left_list = sublink->lefthand;
		List	   *right_list = qtree->targetList;
		int			row_length = list_length(left_list);
		bool		needNot = false;
		List	   *op = sublink->operName;
		char	   *opname = strVal(llast(op));
		ListCell   *l;
		ListCell   *ll_item;

		/* transform lefthand expressions */
		foreach(l, left_list)
			lfirst(l) = transformExpr(pstate, lfirst(l));

		/*
		 * If the expression is "<> ALL" (with unqualified opname) then
		 * convert it to "NOT IN".	This is a hack to improve efficiency of
		 * expressions output by pre-7.4 Postgres.
		 */
		if (sublink->subLinkType == ALL_SUBLINK &&
			list_length(op) == 1 && strcmp(opname, "<>") == 0)
		{
			sublink->subLinkType = ANY_SUBLINK;
			opname = pstrdup("=");
			op = list_make1(makeString(opname));
			sublink->operName = op;
			needNot = true;
		}

		/* Set useOr if op is "<>" (possibly qualified) */
		if (strcmp(opname, "<>") == 0)
			sublink->useOr = TRUE;
		else
			sublink->useOr = FALSE;

		/* Combining operators other than =/<> is dubious... */
		if (row_length != 1 &&
			strcmp(opname, "=") != 0 &&
			strcmp(opname, "<>") != 0)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("row comparison cannot use operator %s",
							opname)));

		/*
		 * To build the list of combining operator OIDs, we must scan
		 * subquery's targetlist to find values that will be matched against
		 * lefthand values.  We need to ignore resjunk targets, so doing the
		 * outer iteration over right_list is easier than doing it over
		 * left_list.
		 */
		sublink->operOids = NIL;

		ll_item = list_head(left_list);
		foreach(l, right_list)
		{
			TargetEntry *tent = (TargetEntry *) lfirst(l);
			Node	   *lexpr;
			Operator	optup;
			Form_pg_operator opform;

			if (tent->resjunk)
				continue;

			if (ll_item == NULL)
				ereport(ERROR,
						(errcode(ERRCODE_SYNTAX_ERROR),
						 errmsg("subquery has too many columns")));
			lexpr = lfirst(ll_item);
			ll_item = lnext(ll_item);

			/*
			 * It's OK to use oper() not compatible_oper() here, because
			 * make_subplan() will insert type coercion calls if needed.
			 */
			optup = oper(op,
						 exprType(lexpr),
						 exprType((Node *) tent->expr),
						 false);
			opform = (Form_pg_operator) GETSTRUCT(optup);

			if (opform->oprresult != BOOLOID)
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
				  errmsg("operator %s must return type boolean, not type %s",
						 opname,
						 format_type_be(opform->oprresult)),
						 errhint("The operator of a quantified predicate subquery must return type boolean.")));

			if (get_func_retset(opform->oprcode))
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("operator %s must not return a set",
								opname),
						 errhint("The operator of a quantified predicate subquery must return type boolean.")));

			sublink->operOids = lappend_oid(sublink->operOids,
											oprid(optup));

			ReleaseSysCache(optup);
		}
		if (ll_item != NULL)
			ereport(ERROR,
					(errcode(ERRCODE_SYNTAX_ERROR),
					 errmsg("subquery has too few columns")));

		if (needNot)
		{
			result = coerce_to_boolean(pstate, result, "NOT");
			result = (Node *) makeBoolExpr(NOT_EXPR,
										   list_make1(result));
		}
	}

	return result;
}

static Node *
transformArrayExpr(ParseState *pstate, ArrayExpr *a)
{
	ArrayExpr  *newa = makeNode(ArrayExpr);
	List	   *newelems = NIL;
	List	   *newcoercedelems = NIL;
	List	   *typeids = NIL;
	ListCell   *element;
	Oid			array_type;
	Oid			element_type;

	/* Transform the element expressions */
	foreach(element, a->elements)
	{
		Node	   *e = (Node *) lfirst(element);
		Node	   *newe;

		newe = transformExpr(pstate, e);
		newelems = lappend(newelems, newe);
		typeids = lappend_oid(typeids, exprType(newe));
	}

	/* Select a common type for the elements */
	element_type = select_common_type(typeids, "ARRAY");

	/* Coerce arguments to common type if necessary */
	foreach(element, newelems)
	{
		Node	   *e = (Node *) lfirst(element);
		Node	   *newe;

		newe = coerce_to_common_type(pstate, e,
									 element_type,
									 "ARRAY");
		newcoercedelems = lappend(newcoercedelems, newe);
	}

	/* Do we have an array type to use? */
	array_type = get_array_type(element_type);
	if (array_type != InvalidOid)
	{
		/* Elements are presumably of scalar type */
		newa->multidims = false;
	}
	else
	{
		/* Must be nested array expressions */
		newa->multidims = true;

		array_type = element_type;
		element_type = get_element_type(array_type);
		if (!OidIsValid(element_type))
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_OBJECT),
					 errmsg("could not find array type for data type %s",
							format_type_be(array_type))));
	}

	newa->array_typeid = array_type;
	newa->element_typeid = element_type;
	newa->elements = newcoercedelems;

	return (Node *) newa;
}

static Node *
transformRowExpr(ParseState *pstate, RowExpr *r)
{
	RowExpr    *newr = makeNode(RowExpr);
	List	   *newargs = NIL;
	ListCell   *arg;

	/* Transform the field expressions */
	foreach(arg, r->args)
	{
		Node	   *e = (Node *) lfirst(arg);
		Node	   *newe;

		newe = transformExpr(pstate, e);
		newargs = lappend(newargs, newe);
	}
	newr->args = newargs;

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

	return (Node *) newr;
}

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

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

		newe = transformExpr(pstate, e);
		newargs = lappend(newargs, newe);
		typeids = lappend_oid(typeids, exprType(newe));
	}

	newc->coalescetype = select_common_type(typeids, "COALESCE");

	/* 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;
	return (Node *) newc;
}

static Node *
transformMinMaxExpr(ParseState *pstate, MinMaxExpr *m)
{
	MinMaxExpr *newm = makeNode(MinMaxExpr);
	List	   *newargs = NIL;
	List	   *newcoercedargs = NIL;
	List	   *typeids = NIL;
	ListCell   *args;

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

		newe = transformExpr(pstate, e);
		newargs = lappend(newargs, newe);
		typeids = lappend_oid(typeids, exprType(newe));
	}

	newm->minmaxtype = select_common_type(typeids, "GREATEST/LEAST");

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

		newe = coerce_to_common_type(pstate, e,
									 newm->minmaxtype,
									 "GREATEST/LEAST");
		newcoercedargs = lappend(newcoercedargs, newe);
	}

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

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 *) transformExpr(pstate, (Node *) b->arg);

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

	return (Node *) b;
}

/*
 * Construct a whole-row reference to represent the notation "relation.*".
 *
 * A whole-row reference is a Var with varno set to the correct range
 * table entry, and varattno == 0 to signal that it references the whole
 * tuple.  (Use of zero here is unclean, since it could easily be confused
 * with error cases, but it's not worth changing now.)  The vartype indicates
 * a rowtype; either a named composite type, or RECORD.
 */
static Node *
transformWholeRowRef(ParseState *pstate, char *schemaname, char *relname)
{
	Node	   *result;
	RangeTblEntry *rte;
	int			vnum;
	int			sublevels_up;
	Oid			toid;

	/* Look up the referenced RTE, creating it if needed */

	rte = refnameRangeTblEntry(pstate, schemaname, relname,
							   &sublevels_up);

	if (rte == NULL)
		rte = addImplicitRTE(pstate, makeRangeVar(schemaname, relname));

	vnum = RTERangeTablePosn(pstate, rte, &sublevels_up);

	/* Build the appropriate referencing node */

	switch (rte->rtekind)
	{
		case RTE_RELATION:
			/* relation: the rowtype is a named composite type */
			toid = get_rel_type_id(rte->relid);
			if (!OidIsValid(toid))
				elog(ERROR, "could not find type OID for relation %u",
					 rte->relid);
			result = (Node *) makeVar(vnum,
									  InvalidAttrNumber,
									  toid,
									  -1,
									  sublevels_up);
			break;
		case RTE_FUNCTION:
			toid = exprType(rte->funcexpr);
			if (toid == RECORDOID || get_typtype(toid) == 'c')
			{
				/* func returns composite; same as relation case */
				result = (Node *) makeVar(vnum,
										  InvalidAttrNumber,
										  toid,
										  -1,
										  sublevels_up);
			}
			else
			{
				/*
				 * func returns scalar; instead of making a whole-row Var,
				 * just reference the function's scalar output.  (XXX this
				 * seems a tad inconsistent, especially if "f.*" was
				 * explicitly written ...)
				 */
				result = (Node *) makeVar(vnum,
										  1,
										  toid,
										  -1,
										  sublevels_up);
			}
			break;
		default:

			/*
			 * RTE is a join or subselect.	We represent this as a whole-row
			 * Var of RECORD type.	(Note that in most cases the Var will be
			 * expanded to a RowExpr during planning, but that is not our
			 * concern here.)
			 */
			result = (Node *) makeVar(vnum,
									  InvalidAttrNumber,
									  RECORDOID,
									  -1,
									  sublevels_up);
			break;
	}

	return result;
}

/*
 *	exprType -
 *	  returns the Oid of the type of the expression. (Used for typechecking.)
 */
Oid
exprType(Node *expr)
{
	Oid			type;

	if (!expr)
		return InvalidOid;

	switch (nodeTag(expr))
	{
		case T_Var:
			type = ((Var *) expr)->vartype;
			break;
		case T_Const:
			type = ((Const *) expr)->consttype;
			break;
		case T_Param:
			type = ((Param *) expr)->paramtype;
			break;
		case T_Aggref:
			type = ((Aggref *) expr)->aggtype;
			break;
		case T_ArrayRef:
			type = ((ArrayRef *) expr)->refrestype;
			break;
		case T_FuncExpr:
			type = ((FuncExpr *) expr)->funcresulttype;
			break;
		case T_OpExpr:
			type = ((OpExpr *) expr)->opresulttype;
			break;
		case T_DistinctExpr:
			type = ((DistinctExpr *) expr)->opresulttype;
			break;
		case T_ScalarArrayOpExpr:
			type = BOOLOID;
			break;
		case T_BoolExpr:
			type = BOOLOID;
			break;
		case T_SubLink:
			{
				SubLink    *sublink = (SubLink *) expr;

				if (sublink->subLinkType == EXPR_SUBLINK ||
					sublink->subLinkType == ARRAY_SUBLINK)
				{
					/* get the type of the subselect's first target column */
					Query	   *qtree = (Query *) sublink->subselect;
					TargetEntry *tent;

					if (!qtree || !IsA(qtree, Query))
						elog(ERROR, "cannot get type for untransformed sublink");
					tent = (TargetEntry *) linitial(qtree->targetList);
					Assert(IsA(tent, TargetEntry));
					Assert(!tent->resjunk);
					type = exprType((Node *) tent->expr);
					if (sublink->subLinkType == ARRAY_SUBLINK)
					{
						type = get_array_type(type);
						if (!OidIsValid(type))
							ereport(ERROR,
									(errcode(ERRCODE_UNDEFINED_OBJECT),
									 errmsg("could not find array type for data type %s",
							format_type_be(exprType((Node *) tent->expr)))));
					}
				}
				else
				{
					/* for all other sublink types, result is boolean */
					type = BOOLOID;
				}
			}
			break;
		case T_SubPlan:
			{
				/*
				 * Although the parser does not ever deal with already-planned
				 * expression trees, we support SubPlan nodes in this routine
				 * for the convenience of ruleutils.c.
				 */
				SubPlan    *subplan = (SubPlan *) expr;

				if (subplan->subLinkType == EXPR_SUBLINK ||
					subplan->subLinkType == ARRAY_SUBLINK)
				{
					/* get the type of the subselect's first target column */
					TargetEntry *tent;

					tent = (TargetEntry *) linitial(subplan->plan->targetlist);
					Assert(IsA(tent, TargetEntry));
					Assert(!tent->resjunk);
					type = exprType((Node *) tent->expr);
					if (subplan->subLinkType == ARRAY_SUBLINK)
					{
						type = get_array_type(type);
						if (!OidIsValid(type))
							ereport(ERROR,
									(errcode(ERRCODE_UNDEFINED_OBJECT),
									 errmsg("could not find array type for data type %s",
							format_type_be(exprType((Node *) tent->expr)))));
					}
				}
				else
				{
					/* for all other subplan types, result is boolean */
					type = BOOLOID;
				}
			}
			break;
		case T_FieldSelect:
			type = ((FieldSelect *) expr)->resulttype;
			break;
		case T_FieldStore:
			type = ((FieldStore *) expr)->resulttype;
			break;
		case T_RelabelType:
			type = ((RelabelType *) expr)->resulttype;
			break;
		case T_ConvertRowtypeExpr:
			type = ((ConvertRowtypeExpr *) expr)->resulttype;
			break;
		case T_CaseExpr:
			type = ((CaseExpr *) expr)->casetype;
			break;
		case T_CaseWhen:
			type = exprType((Node *) ((CaseWhen *) expr)->result);
			break;
		case T_CaseTestExpr:
			type = ((CaseTestExpr *) expr)->typeId;
			break;
		case T_ArrayExpr:
			type = ((ArrayExpr *) expr)->array_typeid;
			break;
		case T_RowExpr:
			type = ((RowExpr *) expr)->row_typeid;
			break;
		case T_CoalesceExpr:
			type = ((CoalesceExpr *) expr)->coalescetype;
			break;
		case T_MinMaxExpr:
			type = ((MinMaxExpr *) expr)->minmaxtype;
			break;
		case T_NullIfExpr:
			type = exprType((Node *) linitial(((NullIfExpr *) expr)->args));
			break;
		case T_NullTest:
			type = BOOLOID;
			break;
		case T_BooleanTest:
			type = BOOLOID;
			break;
		case T_CoerceToDomain:
			type = ((CoerceToDomain *) expr)->resulttype;
			break;
		case T_CoerceToDomainValue:
			type = ((CoerceToDomainValue *) expr)->typeId;
			break;
		case T_SetToDefault:
			type = ((SetToDefault *) expr)->typeId;
			break;
		default:
			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(expr));
			type = InvalidOid;	/* keep compiler quiet */
			break;
	}
	return type;
}

/*
 *	exprTypmod -
 *	  returns the type-specific attrmod of the expression, if it can be
 *	  determined.  In most cases, it can't and we return -1.
 */
int32
exprTypmod(Node *expr)
{
	if (!expr)
		return -1;

	switch (nodeTag(expr))
	{
		case T_Var:
			return ((Var *) expr)->vartypmod;
		case T_Const:
			{
				/* Be smart about string constants... */
				Const	   *con = (Const *) expr;

				switch (con->consttype)
				{
					case BPCHAROID:
						if (!con->constisnull)
						{
							int32		len = VARSIZE(DatumGetPointer(con->constvalue)) - VARHDRSZ;

							/* if multi-byte, take len and find # characters */
							if (pg_database_encoding_max_length() > 1)
								len = pg_mbstrlen_with_len(VARDATA(DatumGetPointer(con->constvalue)), len);
							return len + VARHDRSZ;
						}
						break;
					default:
						break;
				}
			}
			break;
		case T_FuncExpr:
			{
				int32		coercedTypmod;

				/* Be smart about length-coercion functions... */
				if (exprIsLengthCoercion(expr, &coercedTypmod))
					return coercedTypmod;
			}
			break;
		case T_FieldSelect:
			return ((FieldSelect *) expr)->resulttypmod;
		case T_RelabelType:
			return ((RelabelType *) expr)->resulttypmod;
		case T_CaseExpr:
			{
				/*
				 * If all the alternatives agree on type/typmod, return that
				 * typmod, else use -1
				 */
				CaseExpr   *cexpr = (CaseExpr *) expr;
				Oid			casetype = cexpr->casetype;
				int32		typmod;
				ListCell   *arg;

				if (!cexpr->defresult)
					return -1;
				if (exprType((Node *) cexpr->defresult) != casetype)
					return -1;
				typmod = exprTypmod((Node *) cexpr->defresult);
				if (typmod < 0)
					return -1;	/* no point in trying harder */
				foreach(arg, cexpr->args)
				{
					CaseWhen   *w = (CaseWhen *) lfirst(arg);

					Assert(IsA(w, CaseWhen));
					if (exprType((Node *) w->result) != casetype)
						return -1;
					if (exprTypmod((Node *) w->result) != typmod)
						return -1;
				}
				return typmod;
			}
			break;
		case T_CaseTestExpr:
			return ((CaseTestExpr *) expr)->typeMod;
		case T_CoalesceExpr:
			{
				/*
				 * If all the alternatives agree on type/typmod, return that
				 * typmod, else use -1
				 */
				CoalesceExpr *cexpr = (CoalesceExpr *) expr;
				Oid			coalescetype = cexpr->coalescetype;
				int32		typmod;
				ListCell   *arg;

				if (exprType((Node *) linitial(cexpr->args)) != coalescetype)
					return -1;
				typmod = exprTypmod((Node *) linitial(cexpr->args));
				if (typmod < 0)
					return -1;	/* no point in trying harder */
				for_each_cell(arg, lnext(list_head(cexpr->args)))
				{
					Node	   *e = (Node *) lfirst(arg);

					if (exprType(e) != coalescetype)
						return -1;
					if (exprTypmod(e) != typmod)
						return -1;
				}
				return typmod;
			}
			break;
		case T_MinMaxExpr:
			{
				/*
				 * If all the alternatives agree on type/typmod, return that
				 * typmod, else use -1
				 */
				MinMaxExpr *mexpr = (MinMaxExpr *) expr;
				Oid			minmaxtype = mexpr->minmaxtype;
				int32		typmod;
				ListCell   *arg;

				if (exprType((Node *) linitial(mexpr->args)) != minmaxtype)
					return -1;
				typmod = exprTypmod((Node *) linitial(mexpr->args));
				if (typmod < 0)
					return -1;	/* no point in trying harder */
				for_each_cell(arg, lnext(list_head(mexpr->args)))
				{
					Node	   *e = (Node *) lfirst(arg);

					if (exprType(e) != minmaxtype)
						return -1;
					if (exprTypmod(e) != typmod)
						return -1;
				}
				return typmod;
			}
			break;
		case T_NullIfExpr:
			{
				NullIfExpr *nexpr = (NullIfExpr *) expr;

				return exprTypmod((Node *) linitial(nexpr->args));
			}
			break;
		case T_CoerceToDomain:
			return ((CoerceToDomain *) expr)->resulttypmod;
		case T_CoerceToDomainValue:
			return ((CoerceToDomainValue *) expr)->typeMod;
		case T_SetToDefault:
			return ((SetToDefault *) expr)->typeMod;
		default:
			break;
	}
	return -1;
}

/*
 * exprIsLengthCoercion
 *		Detect whether an expression tree is an application of a datatype's
 *		typmod-coercion function.  Optionally extract the result's typmod.
 *
 * If coercedTypmod is not NULL, the typmod is stored there if the expression
 * is a length-coercion function, else -1 is stored there.
 *
 * Note that a combined type-and-length coercion will be treated as a
 * length coercion by this routine.
 */
bool
exprIsLengthCoercion(Node *expr, int32 *coercedTypmod)
{
	FuncExpr   *func;
	int			nargs;
	Const	   *second_arg;

	if (coercedTypmod != NULL)
		*coercedTypmod = -1;	/* default result on failure */

	/* Is it a function-call at all? */
	if (expr == NULL || !IsA(expr, FuncExpr))
		return false;
	func = (FuncExpr *) expr;

	/*
	 * If it didn't come from a coercion context, reject.
	 */
	if (func->funcformat != COERCE_EXPLICIT_CAST &&
		func->funcformat != COERCE_IMPLICIT_CAST)
		return false;

	/*
	 * If it's not a two-argument or three-argument function with the second
	 * argument being an int4 constant, it can't have been created from a
	 * length coercion (it must be a type coercion, instead).
	 */
	nargs = list_length(func->args);
	if (nargs < 2 || nargs > 3)
		return false;

	second_arg = (Const *) lsecond(func->args);
	if (!IsA(second_arg, Const) ||
		second_arg->consttype != INT4OID ||
		second_arg->constisnull)
		return false;

	/*
	 * OK, it is indeed a length-coercion function.
	 */
	if (coercedTypmod != NULL)
		*coercedTypmod = DatumGetInt32(second_arg->constvalue);

	return true;
}

/*
 * Handle an explicit CAST construct.
 *
 * The given expr has already been transformed, but we need to lookup
 * the type name and then apply any necessary coercion function(s).
 */
static Node *
typecast_expression(ParseState *pstate, Node *expr, TypeName *typename)
{
	Oid			inputType = exprType(expr);
	Oid			targetType;

	targetType = typenameTypeId(typename);

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

	expr = coerce_to_target_type(pstate, expr, inputType,
								 targetType, typename->typmod,
								 COERCION_EXPLICIT,
								 COERCE_EXPLICIT_CAST);
	if (expr == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_CANNOT_COERCE),
				 errmsg("cannot cast type %s to %s",
						format_type_be(inputType),
						format_type_be(targetType))));

	return expr;
}

/*
 * Transform a "row op row" construct
 */
static Node *
make_row_op(ParseState *pstate, List *opname, Node *ltree, Node *rtree)
{
	Node	   *result = NULL;
	RowExpr    *lrow,
			   *rrow;
	List	   *largs,
			   *rargs;
	ListCell   *l,
			   *r;
	char	   *oprname;
	BoolExprType boolop;

	/* Inputs are untransformed RowExprs */
	lrow = (RowExpr *) transformExpr(pstate, ltree);
	rrow = (RowExpr *) transformExpr(pstate, rtree);
	Assert(IsA(lrow, RowExpr));
	Assert(IsA(rrow, RowExpr));
	largs = lrow->args;
	rargs = rrow->args;

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

	/*
	 * XXX it's really wrong to generate a simple AND combination for < <= >
	 * >=.	We probably need to invent a new runtime node type to handle those
	 * correctly.  For the moment, though, keep on doing this ...
	 */
	oprname = strVal(llast(opname));

	if ((strcmp(oprname, "=") == 0) ||
		(strcmp(oprname, "<") == 0) ||
		(strcmp(oprname, "<=") == 0) ||
		(strcmp(oprname, ">") == 0) ||
		(strcmp(oprname, ">=") == 0))
		boolop = AND_EXPR;
	else if (strcmp(oprname, "<>") == 0)
		boolop = OR_EXPR;
	else
	{
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("operator %s is not supported for row expressions",
						oprname)));
		boolop = 0;				/* keep compiler quiet */
	}

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

		cmp = (Node *) make_op(pstate, opname, larg, rarg);
		cmp = coerce_to_boolean(pstate, cmp, "row comparison");
		if (result == NULL)
			result = cmp;
		else
			result = (Node *) makeBoolExpr(boolop,
										   list_make2(result, cmp));
	}

	if (result == NULL)
	{
		/* zero-length rows?  Generate constant TRUE or FALSE */
		if (boolop == AND_EXPR)
			result = makeBoolConst(true, false);
		else
			result = makeBoolConst(false, false);
	}

	return result;
}

/*
 * Transform a "row IS DISTINCT FROM row" construct
 */
static Node *
make_row_distinct_op(ParseState *pstate, List *opname,
					 Node *ltree, Node *rtree)
{
	Node	   *result = NULL;
	RowExpr    *lrow,
			   *rrow;
	List	   *largs,
			   *rargs;
	ListCell   *l,
			   *r;

	/* Inputs are untransformed RowExprs */
	lrow = (RowExpr *) transformExpr(pstate, ltree);
	rrow = (RowExpr *) transformExpr(pstate, rtree);
	Assert(IsA(lrow, RowExpr));
	Assert(IsA(rrow, RowExpr));
	largs = lrow->args;
	rargs = rrow->args;

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

	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);
		if (result == NULL)
			result = cmp;
		else
			result = (Node *) makeBoolExpr(OR_EXPR,
										   list_make2(result, cmp));
	}

	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)
{
	Expr	   *result;

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

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

	return result;
}
