/*-------------------------------------------------------------------------
 *
 * parse_expr.c
 *	  handle expressions in parser
 *
 * Portions Copyright (c) 1996-2011, 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_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 *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".
 * 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(pstate, val, con->location);
				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_A_ArrayExpr:
			result = transformArrayExpr(pstate, (A_ArrayExpr *) expr,
										InvalidOid, InvalidOid, -1);
			break;

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

				if (tc->typeName->collnames)
					ereport(ERROR,
							(errcode(ERRCODE_SYNTAX_ERROR),
							 errmsg("COLLATE clause not allowed in cast target"),
							 parser_errposition(pstate, tc->typeName->location)));

				/*
				 * 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);
				}
				break;
			}

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

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

				na->arg = (Expr *) transformExpr(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 *) transformExpr(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_ScalarArrayOpExpr:
		case T_NullIfExpr:
		case T_BoolExpr:
		case T_FieldSelect:
		case T_FieldStore:
		case T_RelabelType:
		case T_CoerceViaIO:
		case T_ArrayCoerceExpr:
		case T_ConvertRowtypeExpr:
		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));
			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),
														   exprCollation(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),
												   exprCollation(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:
				if (relname)
					ereport(ERROR,
							(errcode(ERRCODE_UNDEFINED_COLUMN),
							 errmsg("column %s.%s does not exist",
									relname, colname),
							 parser_errposition(pstate, cref->location)));

				else
					ereport(ERROR,
							(errcode(ERRCODE_UNDEFINED_COLUMN),
							 errmsg("column \"%s\" does not exist",
									colname),
							 parser_errposition(pstate, 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 (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 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 = transformExpr(pstate, (Node *) s);
	}
	else if (lexpr && IsA(lexpr, RowExpr) &&
			 rexpr && IsA(rexpr, RowExpr))
	{
		/* "row op row" */
		lexpr = transformExpr(pstate, lexpr);
		rexpr = transformExpr(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 = transformExpr(pstate, lexpr);
		rexpr = transformExpr(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 = 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),
								 a->location);
}

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),
								 a->location);
}

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),
								 a->location);
}

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,
										 a->location);
}

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,
										 a->location);
}

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

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

	/*
	 * 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 a list of type names. Will result
	 * in a boolean constant node.
	 */
	Node	   *lexpr = transformExpr(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 = transformExpr(pstate, a->lexpr);
	haveRowExpr = (lexpr && IsA(lexpr, RowExpr));
	rexprs = rvars = rnonvars = NIL;
	foreach(l, (List *) a->rexpr)
	{
		Node	   *rexpr = transformExpr(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;
			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, transformExpr(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 = 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);
		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 *) 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);
		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 *) 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
	 */
	resultexprs = lcons(newc->defresult, resultexprs);

	ptype = select_common_type(pstate, resultexprs, "CASE", NULL);
	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");
	}

	newc->casecollation = select_common_collation(pstate, resultexprs, true);

	newc->location = c->location;

	return (Node *) newc;
}

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

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

	pstate->p_hasSubLinks = true;
	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");
	if (qtree->intoClause)
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("subquery cannot have SELECT INTO"),
				 parser_errposition(pstate,
								 exprLocation((Node *) qtree->intoClause))));

	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 = transformExpr(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->paramcollation = 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 = transformExpr(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;
	newa->element_typeid = element_type;
	newa->elements = newcoercedelems;
	newa->location = a->location;

	return (Node *) newa;
}

static Node *
transformRowExpr(ParseState *pstate, RowExpr *r)
{
	RowExpr    *newr = makeNode(RowExpr);

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

	/* Barring later casting, we consider the type RECORD */
	newr->row_typeid = RECORDOID;
	newr->row_format = COERCE_IMPLICIT_CAST;
	newr->colnames = NIL;		/* ROW() has anonymous columns */
	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 = transformExpr(pstate, e);
		newargs = lappend(newargs, newe);
	}

	newc->coalescetype = select_common_type(pstate, newargs, "COALESCE", NULL);

	/* 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->coalescecollation = select_common_collation(pstate, newcoercedargs, true);
	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 = transformExpr(pstate, e);
		newargs = lappend(newargs, newe);
	}

	newm->minmaxtype = select_common_type(pstate, newargs, funcname, NULL);
	newm->collid = select_common_collation(pstate, newargs, false);

	/* 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 = makeNode(XmlExpr);
	ListCell   *lc;
	int			i;

	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->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 = transformExpr(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 = transformExpr(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,
											 transformExpr(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 *) transformExpr(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 */
	result = makeWholeRowVar(rte, vnum, sublevels_up);

	/* 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 = transformExpr(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)
{
	CollateClause *newc;
	Oid		argtype;

	newc = makeNode(CollateClause);
	newc->arg = (Expr *) transformExpr(pstate, (Node *) 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_SYNTAX_ERROR),
				 errmsg("collations are not supported by type %s",
						format_type_be(argtype))));

	newc->collOid = LookupCollation(pstate, c->collnames, c->location);
	newc->collnames = c->collnames;
	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;
	List	   *collids;
	ListCell   *l,
			   *r;
	List	  **opfamily_lists;
	List	  **opstrat_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.
	 */
	opfamily_lists = (List **) palloc(nopers * sizeof(List *));
	opstrat_lists = (List **) palloc(nopers * sizeof(List *));
	strats = NULL;
	i = 0;
	foreach(l, opexprs)
	{
		Oid			opno = ((OpExpr *) lfirst(l))->opno;
		Bitmapset  *this_strats;
		ListCell   *j;

		get_op_btree_interpretation(opno,
									&opfamily_lists[i], &opstrat_lists[i]);

		/*
		 * convert strategy number list to a Bitmapset to make the
		 * intersection calculation easy.
		 */
		this_strats = NULL;
		foreach(j, opstrat_lists[i])
		{
			this_strats = bms_add_member(this_strats, lfirst_int(j));
		}
		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;

		forboth(l, opfamily_lists[i], r, opstrat_lists[i])
		{
			int			opstrat = lfirst_int(r);

			if (opstrat == rctype)
			{
				opfamily = lfirst_oid(l);
				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;
	collids = NIL;
	largs = NIL;
	rargs = NIL;
	foreach(l, opexprs)
	{
		OpExpr	   *cmp = (OpExpr *) lfirst(l);

		opnos = lappend_oid(opnos, cmp->opno);
		collids = lappend_oid(collids, cmp->collid);
		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->collids = collids;
	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;
}
