rewriteHandler.c

/*-------------------------------------------------------------------------
 *
 * rewriteHandler.c
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.49 1999/07/13 21:17:35 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <string.h>
#include "postgres.h"
#include "miscadmin.h"
#include "utils/palloc.h"
#include "utils/elog.h"
#include "utils/rel.h"
#include "nodes/pg_list.h"
#include "nodes/primnodes.h"
#include "nodes/relation.h"

#include "parser/parsetree.h"	/* for parsetree manipulation */
#include "parser/parse_relation.h"
#include "nodes/parsenodes.h"

#include "parser/parse_node.h"
#include "parser/parse_target.h"

#include "parser/analyze.h"
#include "optimizer/clauses.h"
#include "optimizer/prep.h"

#include "rewrite/rewriteSupport.h"
#include "rewrite/rewriteHandler.h"
#include "rewrite/rewriteManip.h"
#include "rewrite/locks.h"

#include "commands/creatinh.h"
#include "access/heapam.h"

#include "utils/lsyscache.h"
#include "utils/syscache.h"
#include "utils/acl.h"
#include "catalog/pg_shadow.h"
#include "catalog/pg_type.h"


static RewriteInfo *gatherRewriteMeta(Query *parsetree,
				  Query *rule_action,
				  Node *rule_qual,
				  int rt_index,
				  CmdType event,
				  bool *instead_flag);
static bool rangeTableEntry_used(Node *node, int rt_index, int sublevels_up);
static bool attribute_used(Node *node, int rt_index, int attno, int sublevels_up);
static void modifyAggrefUplevel(Node *node);
static void modifyAggrefChangeVarnodes(Node **nodePtr, int rt_index, int new_index, int sublevels_up);
static void modifyAggrefDropQual(Node **nodePtr, Node *orignode, Expr *expr);
static SubLink *modifyAggrefMakeSublink(Expr *origexp, Query *parsetree);
static void modifyAggrefQual(Node **nodePtr, Query *parsetree);
static bool checkQueryHasAggs(Node *node);
static bool checkQueryHasAggs_walker(Node *node, void *context);
static bool checkQueryHasSubLink(Node *node);
static bool checkQueryHasSubLink_walker(Node *node, void *context);
static Query *fireRIRrules(Query *parsetree);
static Query *Except_Intersect_Rewrite(Query *parsetree);
static void check_targetlists_are_compatible(List *prev_target,
											 List *current_target);
static void create_intersect_list(Node *ptr, List **intersect_list);
static Node *intersect_tree_analyze(Node *tree, Node *first_select,
									Node *parsetree);

/*
 * gatherRewriteMeta -
 *	  Gather meta information about parsetree, and rule. Fix rule body
 *	  and qualifier so that they can be mixed with the parsetree and
 *	  maintain semantic validity
 */
static RewriteInfo *
gatherRewriteMeta(Query *parsetree,
				  Query *rule_action,
				  Node *rule_qual,
				  int rt_index,
				  CmdType event,
				  bool *instead_flag)
{
	RewriteInfo *info;
	int			rt_length;
	int			result_reln;

	info = (RewriteInfo *) palloc(sizeof(RewriteInfo));
	info->rt_index = rt_index;
	info->event = event;
	info->instead_flag = *instead_flag;
	info->rule_action = (Query *) copyObject(rule_action);
	info->rule_qual = (Node *) copyObject(rule_qual);
	if (info->rule_action == NULL)
		info->nothing = TRUE;
	else
	{
		info->nothing = FALSE;
		info->action = info->rule_action->commandType;
		info->current_varno = rt_index;
		info->rt = parsetree->rtable;
		rt_length = length(info->rt);
		info->rt = nconc(info->rt, copyObject(info->rule_action->rtable));

		info->new_varno = PRS2_NEW_VARNO + rt_length;
		OffsetVarNodes(info->rule_action->qual, rt_length, 0);
		OffsetVarNodes((Node *) info->rule_action->targetList, rt_length, 0);
		OffsetVarNodes(info->rule_qual, rt_length, 0);
		ChangeVarNodes((Node *) info->rule_action->qual,
					   PRS2_CURRENT_VARNO + rt_length, rt_index, 0);
		ChangeVarNodes((Node *) info->rule_action->targetList,
					   PRS2_CURRENT_VARNO + rt_length, rt_index, 0);
		ChangeVarNodes(info->rule_qual,
					   PRS2_CURRENT_VARNO + rt_length, rt_index, 0);

		/*
		 * bug here about replace CURRENT  -- sort of replace current is
		 * deprecated now so this code shouldn't really need to be so
		 * clutzy but.....
		 */
		if (info->action != CMD_SELECT)
		{						/* i.e update XXXXX */
			int			new_result_reln = 0;

			result_reln = info->rule_action->resultRelation;
			switch (result_reln)
			{
				case PRS2_CURRENT_VARNO:
					new_result_reln = rt_index;
					break;
				case PRS2_NEW_VARNO:	/* XXX */
				default:
					new_result_reln = result_reln + rt_length;
					break;
			}
			info->rule_action->resultRelation = new_result_reln;
		}
	}
	return info;
}


/*
 * rangeTableEntry_used -
 *	we need to process a RTE for RIR rules only if it is
 *	referenced somewhere in var nodes of the query.
 */
static bool
rangeTableEntry_used(Node *node, int rt_index, int sublevels_up)
{
	if (node == NULL)
		return FALSE;

	switch (nodeTag(node))
	{
		case T_TargetEntry:
			{
				TargetEntry *tle = (TargetEntry *) node;

				return rangeTableEntry_used(
											(Node *) (tle->expr),
											rt_index,
											sublevels_up);
			}
			break;

		case T_Aggref:
			{
				Aggref	   *aggref = (Aggref *) node;

				return rangeTableEntry_used(
											(Node *) (aggref->target),
											rt_index,
											sublevels_up);
			}
			break;

		case T_GroupClause:
			return FALSE;

		case T_Expr:
			{
				Expr	   *exp = (Expr *) node;

				return rangeTableEntry_used(
											(Node *) (exp->args),
											rt_index,
											sublevels_up);
			}
			break;

		case T_Iter:
			{
				Iter	   *iter = (Iter *) node;

				return rangeTableEntry_used(
											(Node *) (iter->iterexpr),
											rt_index,
											sublevels_up);
			}
			break;

		case T_ArrayRef:
			{
				ArrayRef   *ref = (ArrayRef *) node;

				if (rangeTableEntry_used(
										 (Node *) (ref->refupperindexpr),
										 rt_index,
										 sublevels_up))
					return TRUE;

				if (rangeTableEntry_used(
										 (Node *) (ref->reflowerindexpr),
										 rt_index,
										 sublevels_up))
					return TRUE;

				if (rangeTableEntry_used(
										 (Node *) (ref->refexpr),
										 rt_index,
										 sublevels_up))
					return TRUE;

				if (rangeTableEntry_used(
										 (Node *) (ref->refassgnexpr),
										 rt_index,
										 sublevels_up))
					return TRUE;

				return FALSE;
			}
			break;

		case T_Var:
			{
				Var		   *var = (Var *) node;

				if (var->varlevelsup == sublevels_up)
					return var->varno == rt_index;
				else
					return FALSE;
			}
			break;

		case T_Param:
			return FALSE;

		case T_Const:
			return FALSE;

		case T_List:
			{
				List	   *l;

				foreach(l, (List *) node)
				{
					if (rangeTableEntry_used(
											 (Node *) lfirst(l),
											 rt_index,
											 sublevels_up))
						return TRUE;
				}
				return FALSE;
			}
			break;

		case T_SubLink:
			{
				SubLink    *sub = (SubLink *) node;

				if (rangeTableEntry_used(
										 (Node *) (sub->lefthand),
										 rt_index,
										 sublevels_up))
					return TRUE;

				if (rangeTableEntry_used(
										 (Node *) (sub->subselect),
										 rt_index,
										 sublevels_up + 1))
					return TRUE;

				return FALSE;
			}
			break;

		case T_CaseExpr:
			{
				CaseExpr   *exp = (CaseExpr *) node;

				if (rangeTableEntry_used(
										 (Node *) (exp->args),
										 rt_index,
										 sublevels_up))
					return TRUE;

				if (rangeTableEntry_used(
										 (Node *) (exp->defresult),
										 rt_index,
										 sublevels_up))
					return TRUE;

				return FALSE;
			}
			break;

		case T_CaseWhen:
			{
				CaseWhen   *when = (CaseWhen *) node;

				if (rangeTableEntry_used(
										 (Node *) (when->expr),
										 rt_index,
										 sublevels_up))
					return TRUE;

				if (rangeTableEntry_used(
										 (Node *) (when->result),
										 rt_index,
										 sublevels_up))
					return TRUE;

				return FALSE;
			}
			break;

		case T_Query:
			{
				Query	   *qry = (Query *) node;

				if (rangeTableEntry_used(
										 (Node *) (qry->targetList),
										 rt_index,
										 sublevels_up))
					return TRUE;

				if (rangeTableEntry_used(
										 (Node *) (qry->qual),
										 rt_index,
										 sublevels_up))
					return TRUE;

				if (rangeTableEntry_used(
										 (Node *) (qry->havingQual),
										 rt_index,
										 sublevels_up))
					return TRUE;

				return FALSE;
			}
			break;

		default:
			elog(NOTICE, "unknown node tag %d in rangeTableEntry_used()", nodeTag(node));
			elog(NOTICE, "Node is: %s", nodeToString(node));
			break;


	}

	return FALSE;
}


/*
 * attribute_used -
 *	Check if a specific attribute number of a RTE is used
 *	somewhere in the query
 */
static bool
attribute_used(Node *node, int rt_index, int attno, int sublevels_up)
{
	if (node == NULL)
		return FALSE;

	switch (nodeTag(node))
	{
		case T_TargetEntry:
			{
				TargetEntry *tle = (TargetEntry *) node;

				return attribute_used(
									  (Node *) (tle->expr),
									  rt_index,
									  attno,
									  sublevels_up);
			}
			break;

		case T_Aggref:
			{
				Aggref	   *aggref = (Aggref *) node;

				return attribute_used(
									  (Node *) (aggref->target),
									  rt_index,
									  attno,
									  sublevels_up);
			}
			break;

		case T_GroupClause:
			return FALSE;

		case T_Expr:
			{
				Expr	   *exp = (Expr *) node;

				return attribute_used(
									  (Node *) (exp->args),
									  rt_index,
									  attno,
									  sublevels_up);
			}
			break;

		case T_Iter:
			{
				Iter	   *iter = (Iter *) node;

				return attribute_used(
									  (Node *) (iter->iterexpr),
									  rt_index,
									  attno,
									  sublevels_up);
			}
			break;

		case T_ArrayRef:
			{
				ArrayRef   *ref = (ArrayRef *) node;

				if (attribute_used(
								   (Node *) (ref->refupperindexpr),
								   rt_index,
								   attno,
								   sublevels_up))
					return TRUE;

				if (attribute_used(
								   (Node *) (ref->reflowerindexpr),
								   rt_index,
								   attno,
								   sublevels_up))
					return TRUE;

				if (attribute_used(
								   (Node *) (ref->refexpr),
								   rt_index,
								   attno,
								   sublevels_up))
					return TRUE;

				if (attribute_used(
								   (Node *) (ref->refassgnexpr),
								   rt_index,
								   attno,
								   sublevels_up))
					return TRUE;

				return FALSE;
			}
			break;

		case T_Var:
			{
				Var		   *var = (Var *) node;

				if (var->varlevelsup == sublevels_up)
					return var->varno == rt_index;
				else
					return FALSE;
			}
			break;

		case T_Param:
			return FALSE;

		case T_Const:
			return FALSE;

		case T_List:
			{
				List	   *l;

				foreach(l, (List *) node)
				{
					if (attribute_used(
									   (Node *) lfirst(l),
									   rt_index,
									   attno,
									   sublevels_up))
						return TRUE;
				}
				return FALSE;
			}
			break;

		case T_SubLink:
			{
				SubLink    *sub = (SubLink *) node;

				if (attribute_used(
								   (Node *) (sub->lefthand),
								   rt_index,
								   attno,
								   sublevels_up))
					return TRUE;

				if (attribute_used(
								   (Node *) (sub->subselect),
								   rt_index,
								   attno,
								   sublevels_up + 1))
					return TRUE;

				return FALSE;
			}
			break;

		case T_Query:
			{
				Query	   *qry = (Query *) node;

				if (attribute_used(
								   (Node *) (qry->targetList),
								   rt_index,
								   attno,
								   sublevels_up))
					return TRUE;

				if (attribute_used(
								   (Node *) (qry->qual),
								   rt_index,
								   attno,
								   sublevels_up))
					return TRUE;

				if (attribute_used(
								   (Node *) (qry->havingQual),
								   rt_index,
								   attno,
								   sublevels_up))
					return TRUE;

				return FALSE;
			}
			break;

		default:
			elog(NOTICE, "unknown node tag %d in attribute_used()", nodeTag(node));
			elog(NOTICE, "Node is: %s", nodeToString(node));
			break;


	}

	return FALSE;
}


/*
 * modifyAggrefUplevel -
 *	In the newly created sublink for an aggregate column used in
 *	the qualification, we must adjust the varlevelsup in all the
 *	var nodes.
 */
static void
modifyAggrefUplevel(Node *node)
{
	if (node == NULL)
		return;

	switch (nodeTag(node))
	{
		case T_TargetEntry:
			{
				TargetEntry *tle = (TargetEntry *) node;

				modifyAggrefUplevel(
									(Node *) (tle->expr));
			}
			break;

		case T_Aggref:
			{
				Aggref	   *aggref = (Aggref *) node;

				modifyAggrefUplevel(
									(Node *) (aggref->target));
			}
			break;

		case T_Expr:
			{
				Expr	   *exp = (Expr *) node;

				modifyAggrefUplevel(
									(Node *) (exp->args));
			}
			break;

		case T_Iter:
			{
				Iter	   *iter = (Iter *) node;

				modifyAggrefUplevel(
									(Node *) (iter->iterexpr));
			}
			break;

		case T_ArrayRef:
			{
				ArrayRef   *ref = (ArrayRef *) node;

				modifyAggrefUplevel(
									(Node *) (ref->refupperindexpr));
				modifyAggrefUplevel(
									(Node *) (ref->reflowerindexpr));
				modifyAggrefUplevel(
									(Node *) (ref->refexpr));
				modifyAggrefUplevel(
									(Node *) (ref->refassgnexpr));
			}
			break;

		case T_Var:
			{
				Var		   *var = (Var *) node;

				var->varlevelsup++;
			}
			break;

		case T_Param:
			break;

		case T_Const:
			break;

		case T_List:
			{
				List	   *l;

				foreach(l, (List *) node)
					modifyAggrefUplevel(
										(Node *) lfirst(l));
			}
			break;

		case T_SubLink:
			{
				SubLink    *sub = (SubLink *) node;

				modifyAggrefUplevel(
									(Node *) (sub->lefthand));

				modifyAggrefUplevel(
									(Node *) (sub->oper));

				modifyAggrefUplevel(
									(Node *) (sub->subselect));
			}
			break;

		case T_Query:
			{
				Query	   *qry = (Query *) node;

				modifyAggrefUplevel(
									(Node *) (qry->targetList));

				modifyAggrefUplevel(
									(Node *) (qry->qual));

				modifyAggrefUplevel(
									(Node *) (qry->havingQual));

			}
			break;

		default:
			elog(NOTICE, "unknown node tag %d in modifyAggrefUplevel()", nodeTag(node));
			elog(NOTICE, "Node is: %s", nodeToString(node));
			break;


	}
}


/*
 * modifyAggrefChangeVarnodes -
 *	Change the var nodes in a sublink created for an aggregate column
 *	used in the qualification that is subject of the aggregate
 *	function to point to the correct local RTE.
 */
static void
modifyAggrefChangeVarnodes(Node **nodePtr, int rt_index, int new_index, int sublevels_up)
{
	Node	   *node = *nodePtr;

	if (node == NULL)
		return;

	switch (nodeTag(node))
	{
		case T_TargetEntry:
			{
				TargetEntry *tle = (TargetEntry *) node;

				modifyAggrefChangeVarnodes(
										   (Node **) (&(tle->expr)),
										   rt_index,
										   new_index,
										   sublevels_up);
			}
			break;

		case T_Aggref:
			{
				Aggref	   *aggref = (Aggref *) node;

				modifyAggrefChangeVarnodes(
										   (Node **) (&(aggref->target)),
										   rt_index,
										   new_index,
										   sublevels_up);
			}
			break;

		case T_GroupClause:
			break;

		case T_Expr:
			{
				Expr	   *exp = (Expr *) node;

				modifyAggrefChangeVarnodes(
										   (Node **) (&(exp->args)),
										   rt_index,
										   new_index,
										   sublevels_up);
			}
			break;

		case T_Iter:
			{
				Iter	   *iter = (Iter *) node;

				modifyAggrefChangeVarnodes(
										   (Node **) (&(iter->iterexpr)),
										   rt_index,
										   new_index,
										   sublevels_up);
			}
			break;

		case T_ArrayRef:
			{
				ArrayRef   *ref = (ArrayRef *) node;

				modifyAggrefChangeVarnodes(
									 (Node **) (&(ref->refupperindexpr)),
										   rt_index,
										   new_index,
										   sublevels_up);
				modifyAggrefChangeVarnodes(
									 (Node **) (&(ref->reflowerindexpr)),
										   rt_index,
										   new_index,
										   sublevels_up);
				modifyAggrefChangeVarnodes(
										   (Node **) (&(ref->refexpr)),
										   rt_index,
										   new_index,
										   sublevels_up);
				modifyAggrefChangeVarnodes(
										(Node **) (&(ref->refassgnexpr)),
										   rt_index,
										   new_index,
										   sublevels_up);
			}
			break;

		case T_Var:
			{
				Var		   *var = (Var *) node;

				if (var->varlevelsup == sublevels_up &&
					var->varno == rt_index)
				{
					var = copyObject(var);
					var->varno = new_index;
					var->varnoold = new_index;
					var->varlevelsup = 0;

					*nodePtr = (Node *) var;
				}
			}
			break;

		case T_Param:
			break;

		case T_Const:
			break;

		case T_List:
			{
				List	   *l;

				foreach(l, (List *) node)
					modifyAggrefChangeVarnodes(
											   (Node **) (&lfirst(l)),
											   rt_index,
											   new_index,
											   sublevels_up);
			}
			break;

		case T_SubLink:
			{
				SubLink    *sub = (SubLink *) node;

				modifyAggrefChangeVarnodes(
										   (Node **) (&(sub->lefthand)),
										   rt_index,
										   new_index,
										   sublevels_up);

				modifyAggrefChangeVarnodes(
										   (Node **) (&(sub->oper)),
										   rt_index,
										   new_index,
										   sublevels_up);

				modifyAggrefChangeVarnodes(
										   (Node **) (&(sub->subselect)),
										   rt_index,
										   new_index,
										   sublevels_up + 1);
			}
			break;

		case T_Query:
			{
				Query	   *qry = (Query *) node;

				modifyAggrefChangeVarnodes(
										   (Node **) (&(qry->targetList)),
										   rt_index,
										   new_index,
										   sublevels_up);

				modifyAggrefChangeVarnodes(
										   (Node **) (&(qry->qual)),
										   rt_index,
										   new_index,
										   sublevels_up);

				modifyAggrefChangeVarnodes(
										   (Node **) (&(qry->havingQual)),
										   rt_index,
										   new_index,
										   sublevels_up);
			}
			break;

		default:
			elog(NOTICE, "unknown node tag %d in modifyAggrefChangeVarnodes()", nodeTag(node));
			elog(NOTICE, "Node is: %s", nodeToString(node));
			break;


	}
}


/*
 * modifyAggrefDropQual -
 *	remove the pure aggref clase from a qualification
 */
static void
modifyAggrefDropQual(Node **nodePtr, Node *orignode, Expr *expr)
{
	Node	   *node = *nodePtr;

	if (node == NULL)
		return;

	switch (nodeTag(node))
	{
		case T_Var:
			break;

		case T_Aggref:
			{
				Aggref	   *aggref = (Aggref *) node;
				Aggref	   *oaggref = (Aggref *) orignode;

				modifyAggrefDropQual(
									 (Node **) (&(aggref->target)),
									 (Node *) (oaggref->target),
									 expr);
			}
			break;

		case T_Param:
			break;

		case T_Const:
			break;

		case T_GroupClause:
			break;

		case T_Expr:
			{
				Expr	   *this_expr = (Expr *) node;
				Expr	   *orig_expr = (Expr *) orignode;

				if (orig_expr == expr)
				{
					Const	   *ctrue;

					if (expr->typeOid != BOOLOID)
						elog(ERROR,
							 "aggregate expression in qualification isn't of type bool");
					ctrue = makeNode(Const);
					ctrue->consttype = BOOLOID;
					ctrue->constlen = 1;
					ctrue->constisnull = FALSE;
					ctrue->constvalue = (Datum) TRUE;
					ctrue->constbyval = TRUE;

					*nodePtr = (Node *) ctrue;
				}
				else
					modifyAggrefDropQual(
										 (Node **) (&(this_expr->args)),
										 (Node *) (orig_expr->args),
										 expr);
			}
			break;

		case T_Iter:
			{
				Iter	   *iter = (Iter *) node;
				Iter	   *oiter = (Iter *) orignode;

				modifyAggrefDropQual(
									 (Node **) (&(iter->iterexpr)),
									 (Node *) (oiter->iterexpr),
									 expr);
			}
			break;

		case T_ArrayRef:
			{
				ArrayRef   *ref = (ArrayRef *) node;
				ArrayRef   *oref = (ArrayRef *) orignode;

				modifyAggrefDropQual(
									 (Node **) (&(ref->refupperindexpr)),
									 (Node *) (oref->refupperindexpr),
									 expr);
				modifyAggrefDropQual(
									 (Node **) (&(ref->reflowerindexpr)),
									 (Node *) (oref->reflowerindexpr),
									 expr);
				modifyAggrefDropQual(
									 (Node **) (&(ref->refexpr)),
									 (Node *) (oref->refexpr),
									 expr);
				modifyAggrefDropQual(
									 (Node **) (&(ref->refassgnexpr)),
									 (Node *) (oref->refassgnexpr),
									 expr);
			}
			break;

		case T_List:
			{
				List	   *l;
				List	   *ol = (List *) orignode;
				int			li = 0;

				foreach(l, (List *) node)
				{
					modifyAggrefDropQual(
										 (Node **) (&(lfirst(l))),
										 (Node *) nth(li, ol),
										 expr);
					li++;
				}
			}
			break;

		case T_SubLink:
			{
				SubLink    *sub = (SubLink *) node;
				SubLink    *osub = (SubLink *) orignode;

				modifyAggrefDropQual(
									 (Node **) (&(sub->subselect)),
									 (Node *) (osub->subselect),
									 expr);
			}
			break;

		case T_Query:
			{
				Query	   *qry = (Query *) node;
				Query	   *oqry = (Query *) orignode;

				modifyAggrefDropQual(
									 (Node **) (&(qry->qual)),
									 (Node *) (oqry->qual),
									 expr);

				modifyAggrefDropQual(
									 (Node **) (&(qry->havingQual)),
									 (Node *) (oqry->havingQual),
									 expr);
			}
			break;

		default:
			elog(NOTICE, "unknown node tag %d in modifyAggrefDropQual()", nodeTag(node));
			elog(NOTICE, "Node is: %s", nodeToString(node));
			break;


	}
}


/*
 * modifyAggrefMakeSublink -
 *	Create a sublink node for a qualification expression that
 *	uses an aggregate column of a view
 */
static SubLink *
modifyAggrefMakeSublink(Expr *origexp, Query *parsetree)
{
	SubLink    *sublink;
	Query	   *subquery;
	Node	   *subqual;
	RangeTblEntry *rte;
	Aggref	   *aggref;
	Var		   *target;
	TargetEntry *tle;
	Resdom	   *resdom;
	Expr	   *exp = copyObject(origexp);

	if (nodeTag(nth(0, exp->args)) == T_Aggref)
	{
		if (nodeTag(nth(1, exp->args)) == T_Aggref)
			elog(ERROR, "rewrite: comparision of 2 aggregate columns not supported");
		else
			elog(ERROR, "rewrite: aggregate column of view must be at rigth side in qual");
	}

	aggref = (Aggref *) nth(1, exp->args);
	target = (Var *) (aggref->target);
	rte = (RangeTblEntry *) nth(target->varno - 1, parsetree->rtable);
	tle = makeNode(TargetEntry);
	resdom = makeNode(Resdom);

	aggref->usenulls = TRUE;

	resdom->resno = 1;
	resdom->restype = ((Oper *) (exp->oper))->opresulttype;
	resdom->restypmod = -1;
	resdom->resname = pstrdup("<noname>");
	resdom->reskey = 0;
	resdom->reskeyop = 0;
	resdom->resjunk = false;

	tle->resdom = resdom;
	tle->expr = (Node *) aggref;

	subqual = copyObject(parsetree->qual);
	modifyAggrefDropQual((Node **) &subqual, (Node *) parsetree->qual, origexp);

	sublink = makeNode(SubLink);
	sublink->subLinkType = EXPR_SUBLINK;
	sublink->useor = FALSE;
	sublink->lefthand = lappend(NIL, copyObject(lfirst(exp->args)));
	sublink->oper = lappend(NIL, copyObject(exp));
	sublink->subselect = NULL;

	subquery = makeNode(Query);
	sublink->subselect = (Node *) subquery;

	subquery->commandType = CMD_SELECT;
	subquery->utilityStmt = NULL;
	subquery->resultRelation = 0;
	subquery->into = NULL;
	subquery->isPortal = FALSE;
	subquery->isBinary = FALSE;
	subquery->isTemp = FALSE;
	subquery->unionall = FALSE;
	subquery->uniqueFlag = NULL;
	subquery->sortClause = NULL;
	subquery->rtable = lappend(NIL, rte);
	subquery->targetList = lappend(NIL, tle);
	subquery->qual = subqual;
	subquery->groupClause = NIL;
	subquery->havingQual = NULL;
	subquery->hasAggs = TRUE;
	subquery->hasSubLinks = FALSE;
	subquery->unionClause = NULL;


	modifyAggrefUplevel((Node *) sublink);

	modifyAggrefChangeVarnodes((Node **) &(sublink->lefthand), target->varno,
							   1, target->varlevelsup);
	modifyAggrefChangeVarnodes((Node **) &(sublink->oper), target->varno,
							   1, target->varlevelsup);
	modifyAggrefChangeVarnodes((Node **) &(sublink->subselect), target->varno,
							   1, target->varlevelsup);

	return sublink;
}


/*
 * modifyAggrefQual -
 *	Search for qualification expressions that contain aggregate
 *	functions and substiture them by sublinks. These expressions
 *	originally come from qualifications that use aggregate columns
 *	of a view.
 */
static void
modifyAggrefQual(Node **nodePtr, Query *parsetree)
{
	Node	   *node = *nodePtr;

	if (node == NULL)
		return;

	switch (nodeTag(node))
	{
		case T_Var:
			break;

		case T_Param:
			break;

		case T_Const:
			break;

		case T_GroupClause:
			break;

		case T_Expr:
			{
				Expr	   *exp = (Expr *) node;
				SubLink    *sub;


				if (length(exp->args) != 2)
				{
					modifyAggrefQual(
									 (Node **) (&(exp->args)),
									 parsetree);
					break;
				}

				if (nodeTag(nth(0, exp->args)) != T_Aggref &&
					nodeTag(nth(1, exp->args)) != T_Aggref)
				{

					modifyAggrefQual(
									 (Node **) (&(exp->args)),
									 parsetree);
					break;
				}

				sub = modifyAggrefMakeSublink(exp,
											  parsetree);

				*nodePtr = (Node *) sub;
				parsetree->hasSubLinks = TRUE;
			}
			break;

		case T_CaseExpr:
			{

				/*
				 * We're calling recursively, and this routine knows how
				 * to handle lists so let it do the work to handle the
				 * WHEN clauses...
				 */
				modifyAggrefQual(
								 (Node **) (&(((CaseExpr *) node)->args)),
								 parsetree);

				modifyAggrefQual(
						   (Node **) (&(((CaseExpr *) node)->defresult)),
								 parsetree);
			}
			break;

		case T_CaseWhen:
			{
				modifyAggrefQual(
								 (Node **) (&(((CaseWhen *) node)->expr)),
								 parsetree);

				modifyAggrefQual(
							  (Node **) (&(((CaseWhen *) node)->result)),
								 parsetree);
			}
			break;

		case T_Iter:
			{
				Iter	   *iter = (Iter *) node;

				modifyAggrefQual(
								 (Node **) (&(iter->iterexpr)),
								 parsetree);
			}
			break;

		case T_ArrayRef:
			{
				ArrayRef   *ref = (ArrayRef *) node;

				modifyAggrefQual(
								 (Node **) (&(ref->refupperindexpr)),
								 parsetree);
				modifyAggrefQual(
								 (Node **) (&(ref->reflowerindexpr)),
								 parsetree);
				modifyAggrefQual(
								 (Node **) (&(ref->refexpr)),
								 parsetree);
				modifyAggrefQual(
								 (Node **) (&(ref->refassgnexpr)),
								 parsetree);
			}
			break;

		case T_List:
			{
				List	   *l;

				foreach(l, (List *) node)
					modifyAggrefQual(
									 (Node **) (&(lfirst(l))),
									 parsetree);
			}
			break;

		case T_SubLink:
			{
				SubLink    *sub = (SubLink *) node;

				modifyAggrefQual(
								 (Node **) (&(sub->subselect)),
								 (Query *) (sub->subselect));
			}
			break;

		case T_Query:
			{
				Query	   *qry = (Query *) node;

				modifyAggrefQual(
								 (Node **) (&(qry->qual)),
								 parsetree);

				modifyAggrefQual(
								 (Node **) (&(qry->havingQual)),
								 parsetree);
			}
			break;

		default:
			elog(NOTICE, "unknown node tag %d in modifyAggrefQual()", nodeTag(node));
			elog(NOTICE, "Node is: %s", nodeToString(node));
			break;


	}
}


/*
 * checkQueryHasAggs -
 *	Queries marked hasAggs might not have them any longer after
 *	rewriting. Check it.
 */
static bool
checkQueryHasAggs(Node *node)
{
	return checkQueryHasAggs_walker(node, NULL);
}

static bool
checkQueryHasAggs_walker(Node *node, void *context)
{
	if (node == NULL)
		return false;
	if (IsA(node, Aggref))
		return true;			/* abort the tree traversal and return true */
	return expression_tree_walker(node, checkQueryHasAggs_walker, context);
}

/*
 * checkQueryHasSubLink -
 *	Queries marked hasSubLinks might not have them any longer after
 *	rewriting. Check it.
 */
static bool
checkQueryHasSubLink(Node *node)
{
	return checkQueryHasSubLink_walker(node, NULL);
}

static bool
checkQueryHasSubLink_walker(Node *node, void *context)
{
	if (node == NULL)
		return false;
	if (IsA(node, SubLink))
		return true;			/* abort the tree traversal and return true */
	/* Note: we assume the tree has not yet been rewritten by subselect.c,
	 * therefore we will find bare SubLink nodes and not SUBPLAN nodes.
	 */
	return expression_tree_walker(node, checkQueryHasSubLink_walker, context);
}


static Node *
FindMatchingTLEntry(List *tlist, char *e_attname)
{
	List	   *i;

	foreach(i, tlist)
	{
		TargetEntry *tle = lfirst(i);
		char	   *resname;

		resname = tle->resdom->resname;
		if (!strcmp(e_attname, resname))
			return (tle->expr);
	}
	return NULL;
}


static Node *
make_null(Oid type)
{
	Const	   *c = makeNode(Const);

	c->consttype = type;
	c->constlen = get_typlen(type);
	c->constvalue = PointerGetDatum(NULL);
	c->constisnull = true;
	c->constbyval = get_typbyval(type);
	return (Node *) c;
}


static void
apply_RIR_adjust_sublevel(Node *node, int sublevels_up)
{
	if (node == NULL)
		return;

	switch (nodeTag(node))
	{
		case T_TargetEntry:
			{
				TargetEntry *tle = (TargetEntry *) node;

				apply_RIR_adjust_sublevel(
										  (Node *) (tle->expr),
										  sublevels_up);
			}
			break;

		case T_Aggref:
			{
				Aggref	   *aggref = (Aggref *) node;

				apply_RIR_adjust_sublevel(
										  (Node *) (aggref->target),
										  sublevels_up);
			}
			break;

		case T_GroupClause:
			break;

		case T_Expr:
			{
				Expr	   *exp = (Expr *) node;

				apply_RIR_adjust_sublevel(
										  (Node *) (exp->args),
										  sublevels_up);
			}
			break;

		case T_Iter:
			{
				Iter	   *iter = (Iter *) node;

				apply_RIR_adjust_sublevel(
										  (Node *) (iter->iterexpr),
										  sublevels_up);
			}
			break;

		case T_ArrayRef:
			{
				ArrayRef   *ref = (ArrayRef *) node;

				apply_RIR_adjust_sublevel(
										  (Node *) (ref->refupperindexpr),
										  sublevels_up);

				apply_RIR_adjust_sublevel(
										  (Node *) (ref->reflowerindexpr),
										  sublevels_up);

				apply_RIR_adjust_sublevel(
										  (Node *) (ref->refexpr),
										  sublevels_up);

				apply_RIR_adjust_sublevel(
										  (Node *) (ref->refassgnexpr),
										  sublevels_up);
			}
			break;

		case T_Var:
			{
				Var		   *var = (Var *) node;

				var->varlevelsup = sublevels_up;
			}
			break;

		case T_Param:
			break;

		case T_Const:
			break;

		case T_List:
			{
				List	   *l;

				foreach(l, (List *) node)
				{
					apply_RIR_adjust_sublevel(
											  (Node *) lfirst(l),
											  sublevels_up);
				}
			}
			break;

		case T_CaseExpr:
			{
				CaseExpr   *exp = (CaseExpr *) node;

				apply_RIR_adjust_sublevel(
										  (Node *) (exp->args),
										  sublevels_up);

				apply_RIR_adjust_sublevel(
										  (Node *) (exp->defresult),
										  sublevels_up);
			}
			break;

		case T_CaseWhen:
			{
				CaseWhen   *exp = (CaseWhen *) node;

				apply_RIR_adjust_sublevel(
										  (Node *) (exp->expr),
										  sublevels_up);

				apply_RIR_adjust_sublevel(
										  (Node *) (exp->result),
										  sublevels_up);
			}
			break;

		default:
			elog(NOTICE, "unknown node tag %d in attribute_used()", nodeTag(node));
			elog(NOTICE, "Node is: %s", nodeToString(node));
			break;


	}
}


static void
apply_RIR_view(Node **nodePtr, int rt_index, RangeTblEntry *rte, List *tlist, int *modified, int sublevels_up)
{
	Node	   *node = *nodePtr;

	if (node == NULL)
		return;

	switch (nodeTag(node))
	{
		case T_TargetEntry:
			{
				TargetEntry *tle = (TargetEntry *) node;

				apply_RIR_view(
							   (Node **) (&(tle->expr)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);
			}
			break;

		case T_Aggref:
			{
				Aggref	   *aggref = (Aggref *) node;

				apply_RIR_view(
							   (Node **) (&(aggref->target)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);
			}
			break;

		case T_GroupClause:
			break;

		case T_Expr:
			{
				Expr	   *exp = (Expr *) node;

				apply_RIR_view(
							   (Node **) (&(exp->args)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);
			}
			break;

		case T_Iter:
			{
				Iter	   *iter = (Iter *) node;

				apply_RIR_view(
							   (Node **) (&(iter->iterexpr)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);
			}
			break;

		case T_ArrayRef:
			{
				ArrayRef   *ref = (ArrayRef *) node;

				apply_RIR_view(
							   (Node **) (&(ref->refupperindexpr)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);
				apply_RIR_view(
							   (Node **) (&(ref->reflowerindexpr)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);
				apply_RIR_view(
							   (Node **) (&(ref->refexpr)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);
				apply_RIR_view(
							   (Node **) (&(ref->refassgnexpr)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);
			}
			break;

		case T_Var:
			{
				Var		   *var = (Var *) node;

				if (var->varlevelsup == sublevels_up &&
					var->varno == rt_index)
				{
					Node	   *exp;

					if (var->varattno < 0)
						elog(ERROR, "system column %s not available - %s is a view", get_attname(rte->relid, var->varattno), rte->relname);
					exp = FindMatchingTLEntry(
											  tlist,
											  get_attname(rte->relid,
														  var->varattno));

					if (exp == NULL)
					{
						*nodePtr = make_null(var->vartype);
						return;
					}

					exp = copyObject(exp);
					if (var->varlevelsup > 0)
						apply_RIR_adjust_sublevel(exp, var->varlevelsup);
					*nodePtr = exp;
					*modified = TRUE;
				}
			}
			break;

		case T_Param:
			break;

		case T_Const:
			break;

		case T_List:
			{
				List	   *l;

				foreach(l, (List *) node)
					apply_RIR_view(
								   (Node **) (&(lfirst(l))),
								   rt_index,
								   rte,
								   tlist,
								   modified,
								   sublevels_up);
			}
			break;

		case T_SubLink:
			{
				SubLink    *sub = (SubLink *) node;
				List	   *tmp_lefthand,
						   *tmp_oper;

				apply_RIR_view(
							   (Node **) (&(sub->lefthand)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);

				apply_RIR_view(
							   (Node **) (&(sub->subselect)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up + 1);

				tmp_lefthand = sub->lefthand;
				foreach(tmp_oper, sub->oper)
				{
					lfirst(((Expr *) lfirst(tmp_oper))->args) =
						lfirst(tmp_lefthand);
					tmp_lefthand = lnext(tmp_lefthand);
				}
			}
			break;

		case T_Query:
			{
				Query	   *qry = (Query *) node;

				apply_RIR_view(
							   (Node **) (&(qry->targetList)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);

				apply_RIR_view(
							   (Node **) (&(qry->qual)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);

				apply_RIR_view(
							   (Node **) (&(qry->havingQual)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);
			}
			break;

		case T_CaseExpr:
			{
				CaseExpr   *exp = (CaseExpr *) node;

				apply_RIR_view(
							   (Node **) (&(exp->args)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);

				apply_RIR_view(
							   (Node **) (&(exp->defresult)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);
			}
			break;

		case T_CaseWhen:
			{
				CaseWhen   *exp = (CaseWhen *) node;

				apply_RIR_view(
							   (Node **) (&(exp->expr)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);

				apply_RIR_view(
							   (Node **) (&(exp->result)),
							   rt_index,
							   rte,
							   tlist,
							   modified,
							   sublevels_up);
			}
			break;

		default:
			elog(NOTICE, "unknown node tag %d in apply_RIR_view()", nodeTag(node));
			elog(NOTICE, "Node is: %s", nodeToString(node));
			break;
	}
}

extern void CheckSelectForUpdate(Query *rule_action);	/* in analyze.c */

static void
ApplyRetrieveRule(Query *parsetree,
				  RewriteRule *rule,
				  int rt_index,
				  int relation_level,
				  Relation relation,
				  int *modified)
{
	Query	   *rule_action = NULL;
	Node	   *rule_qual;
	List	   *rtable,
			   *rt,
			   *l;
	int			nothing,
				rt_length;
	int			badsql = FALSE;

	rule_qual = rule->qual;
	if (rule->actions)
	{
		if (length(rule->actions) > 1)	/* ??? because we don't handle
										 * rules with more than one
										 * action? -ay */

			return;
		rule_action = copyObject(lfirst(rule->actions));
		nothing = FALSE;
	}
	else
		nothing = TRUE;

	rtable = copyObject(parsetree->rtable);
	foreach(rt, rtable)
	{
		RangeTblEntry *rte = lfirst(rt);

		/*
		 * this is to prevent add_missing_vars_to_base_rels() from adding
		 * a bogus entry to the new target list.
		 */
		rte->inFromCl = false;
	}
	rt_length = length(rtable);

	rtable = nconc(rtable, copyObject(rule_action->rtable));
	parsetree->rtable = rtable;

	/* FOR UPDATE of view... */
	foreach(l, parsetree->rowMark)
	{
		if (((RowMark *) lfirst(l))->rti == rt_index)
			break;
	}
	if (l != NULL)				/* oh, hell -:) */
	{
		RowMark    *newrm;
		Index		rti = 1;
		List	   *l2;

		CheckSelectForUpdate(rule_action);

		/*
		 * We believe that rt_index is VIEW - nothing should be marked for
		 * VIEW, but ACL check must be done. As for real tables of VIEW -
		 * their rows must be marked, but we have to skip ACL check for
		 * them.
		 */
		((RowMark *) lfirst(l))->info &= ~ROW_MARK_FOR_UPDATE;
		foreach(l2, rule_action->rtable)
		{

			/*
			 * RTable of VIEW has two entries of VIEW itself - we use
			 * relid to skip them.
			 */
			if (relation->rd_id != ((RangeTblEntry *) lfirst(l2))->relid)
			{
				newrm = makeNode(RowMark);
				newrm->rti = rti + rt_length;
				newrm->info = ROW_MARK_FOR_UPDATE;
				lnext(l) = lcons(newrm, lnext(l));
				l = lnext(l);
			}
			rti++;
		}
	}

	rule_action->rtable = rtable;
	OffsetVarNodes((Node *) rule_qual, rt_length, 0);
	OffsetVarNodes((Node *) rule_action, rt_length, 0);

	ChangeVarNodes((Node *) rule_qual,
				   PRS2_CURRENT_VARNO + rt_length, rt_index, 0);
	ChangeVarNodes((Node *) rule_action,
				   PRS2_CURRENT_VARNO + rt_length, rt_index, 0);

	if (relation_level)
	{
		apply_RIR_view((Node **) &parsetree, rt_index,
					   (RangeTblEntry *) nth(rt_index - 1, rtable),
					   rule_action->targetList, modified, 0);
		apply_RIR_view((Node **) &rule_action, rt_index,
					   (RangeTblEntry *) nth(rt_index - 1, rtable),
					   rule_action->targetList, modified, 0);
	}
	else
	{
		HandleRIRAttributeRule(parsetree, rtable, rule_action->targetList,
							   rt_index, rule->attrno, modified, &badsql);
	}
	if (*modified && !badsql)
	{
		AddQual(parsetree, rule_action->qual);
		AddGroupClause(parsetree, rule_action->groupClause,
					   rule_action->targetList);
		AddHavingQual(parsetree, rule_action->havingQual);
		parsetree->hasAggs = (rule_action->hasAggs || parsetree->hasAggs);
		parsetree->hasSubLinks = (rule_action->hasSubLinks || parsetree->hasSubLinks);
	}
}


static void
fireRIRonSubselect(Node *node)
{
	if (node == NULL)
		return;

	switch (nodeTag(node))
	{
		case T_TargetEntry:
			{
				TargetEntry *tle = (TargetEntry *) node;

				fireRIRonSubselect(
								   (Node *) (tle->expr));
			}
			break;

		case T_Aggref:
			{
				Aggref	   *aggref = (Aggref *) node;

				fireRIRonSubselect(
								   (Node *) (aggref->target));
			}
			break;

		case T_GroupClause:
			break;

		case T_Expr:
			{
				Expr	   *exp = (Expr *) node;

				fireRIRonSubselect(
								   (Node *) (exp->args));
			}
			break;

		case T_Iter:
			{
				Iter	   *iter = (Iter *) node;

				fireRIRonSubselect(
								   (Node *) (iter->iterexpr));
			}
			break;

		case T_ArrayRef:
			{
				ArrayRef   *ref = (ArrayRef *) node;

				fireRIRonSubselect(
								   (Node *) (ref->refupperindexpr));
				fireRIRonSubselect(
								   (Node *) (ref->reflowerindexpr));
				fireRIRonSubselect(
								   (Node *) (ref->refexpr));
				fireRIRonSubselect(
								   (Node *) (ref->refassgnexpr));
			}
			break;

		case T_Var:
			break;

		case T_Param:
			break;

		case T_Const:
			break;

		case T_List:
			{
				List	   *l;

				foreach(l, (List *) node)
					fireRIRonSubselect(
									   (Node *) (lfirst(l)));
			}
			break;

		case T_SubLink:
			{
				SubLink    *sub = (SubLink *) node;
				Query	   *qry;

				fireRIRonSubselect(
								   (Node *) (sub->lefthand));

				qry = fireRIRrules((Query *) (sub->subselect));

				fireRIRonSubselect(
								   (Node *) qry);

				sub->subselect = (Node *) qry;
			}
			break;

		case T_CaseExpr:
			{
				CaseExpr   *exp = (CaseExpr *) node;

				fireRIRonSubselect(
								   (Node *) (exp->args));

				fireRIRonSubselect(
								   (Node *) (exp->defresult));
			}
			break;

		case T_CaseWhen:
			{
				CaseWhen   *exp = (CaseWhen *) node;

				fireRIRonSubselect(
								   (Node *) (exp->expr));

				fireRIRonSubselect(
								   (Node *) (exp->result));
			}
			break;

		case T_Query:
			{
				Query	   *qry = (Query *) node;

				fireRIRonSubselect(
								   (Node *) (qry->targetList));

				fireRIRonSubselect(
								   (Node *) (qry->qual));

				fireRIRonSubselect(
								   (Node *) (qry->havingQual));
			}
			break;

		default:
			elog(NOTICE, "unknown node tag %d in fireRIRonSubselect()", nodeTag(node));
			elog(NOTICE, "Node is: %s", nodeToString(node));
			break;


	}
}


/*
 * fireRIRrules -
 *	Apply all RIR rules on each rangetable entry in a query
 */
static Query *
fireRIRrules(Query *parsetree)
{
	int			rt_index;
	RangeTblEntry *rte;
	Relation	rel;
	List	   *locks;
	RuleLock   *rules;
	RewriteRule *rule;
	RewriteRule RIRonly;
	int			modified;
	int			i;
	List	   *l;

	rt_index = 0;
	while (rt_index < length(parsetree->rtable))
	{
		++rt_index;

		rte = nth(rt_index - 1, parsetree->rtable);

		if (!rangeTableEntry_used((Node *) parsetree, rt_index, 0))
		{

			/*
			 * Unused range table entries must not be marked as coming
			 * from a clause. Otherwise the planner will generate joins
			 * over relations that in fact shouldn't be scanned at all and
			 * the result will contain duplicates
			 *
			 * Jan
			 *
			 */
			rte->inFromCl = FALSE;
			continue;
		}

		rel = heap_openr(rte->relname);
		if (rel->rd_rules == NULL)
		{
			heap_close(rel);
			continue;
		}

		rules = rel->rd_rules;
		locks = NIL;

		/*
		 * Collect the RIR rules that we must apply
		 */
		for (i = 0; i < rules->numLocks; i++)
		{
			rule = rules->rules[i];
			if (rule->event != CMD_SELECT)
				continue;

			if (rule->attrno > 0 &&
				!attribute_used((Node *) parsetree,
								rt_index,
								rule->attrno, 0))
				continue;

			locks = lappend(locks, rule);
		}

		/*
		 * Check permissions
		 */
		checkLockPerms(locks, parsetree, rt_index);

		/*
		 * Now apply them
		 */
		foreach(l, locks)
		{
			rule = lfirst(l);

			RIRonly.event = rule->event;
			RIRonly.attrno = rule->attrno;
			RIRonly.qual = rule->qual;
			RIRonly.actions = rule->actions;

			ApplyRetrieveRule(parsetree,
							  &RIRonly,
							  rt_index,
							  RIRonly.attrno == -1,
							  rel,
							  &modified);
		}

		heap_close(rel);
	}

	fireRIRonSubselect((Node *) parsetree);
	modifyAggrefQual((Node **) &(parsetree->qual), parsetree);

	return parsetree;
}


/*
 * idea is to fire regular rules first, then qualified instead
 * rules and unqualified instead rules last. Any lemming is counted for.
 */
static List *
orderRules(List *locks)
{
	List	   *regular = NIL;
	List	   *instead_rules = NIL;
	List	   *instead_qualified = NIL;
	List	   *i;

	foreach(i, locks)
	{
		RewriteRule *rule_lock = (RewriteRule *) lfirst(i);

		if (rule_lock->isInstead)
		{
			if (rule_lock->qual == NULL)
				instead_rules = lappend(instead_rules, rule_lock);
			else
				instead_qualified = lappend(instead_qualified, rule_lock);
		}
		else
			regular = lappend(regular, rule_lock);
	}
	regular = nconc(regular, instead_qualified);
	return nconc(regular, instead_rules);
}



static Query *
CopyAndAddQual(Query *parsetree,
			   List *actions,
			   Node *rule_qual,
			   int rt_index,
			   CmdType event)
{
	Query	   *new_tree = (Query *) copyObject(parsetree);
	Node	   *new_qual = NULL;
	Query	   *rule_action = NULL;

	if (actions)
		rule_action = lfirst(actions);
	if (rule_qual != NULL)
		new_qual = (Node *) copyObject(rule_qual);
	if (rule_action != NULL)
	{
		List	   *rtable;
		int			rt_length;

		rtable = new_tree->rtable;
		rt_length = length(rtable);
		rtable = nconc(rtable, copyObject(rule_action->rtable));
		new_tree->rtable = rtable;
		OffsetVarNodes(new_qual, rt_length, 0);
		ChangeVarNodes(new_qual, PRS2_CURRENT_VARNO + rt_length, rt_index, 0);
	}
	/* XXX -- where current doesn't work for instead nothing.... yet */
	AddNotQual(new_tree, new_qual);

	return new_tree;
}



/*
 *	fireRules -
 *	   Iterate through rule locks applying rules.
 *	   All rules create their own parsetrees. Instead rules
 *	   with rule qualification save the original parsetree
 *	   and add their negated qualification to it. Real instead
 *	   rules finally throw away the original parsetree.
 *
 *	   remember: reality is for dead birds -- glass
 *
 */
static List *
fireRules(Query *parsetree,
		  int rt_index,
		  CmdType event,
		  bool *instead_flag,
		  List *locks,
		  List **qual_products)
{
	RewriteInfo *info;
	List	   *results = NIL;
	List	   *i;

	/* choose rule to fire from list of rules */
	if (locks == NIL)
		return NIL;

	locks = orderRules(locks);	/* real instead rules last */
	foreach(i, locks)
	{
		RewriteRule *rule_lock = (RewriteRule *) lfirst(i);
		Node	   *qual,
				   *event_qual;
		List	   *actions;
		List	   *r;

		/*
		 * Instead rules change the resultRelation of the query. So the
		 * permission checks on the initial resultRelation would never be
		 * done (this is normally done in the executor deep down). So we
		 * must do it here. The result relations resulting from earlier
		 * rewrites are already checked against the rules eventrelation
		 * owner (during matchLocks) and have the skipAcl flag set.
		 */
		if (rule_lock->isInstead &&
			parsetree->commandType != CMD_SELECT)
		{
			RangeTblEntry *rte;
			int32		acl_rc;
			int32		reqperm;

			switch (parsetree->commandType)
			{
				case CMD_INSERT:
					reqperm = ACL_AP;
					break;
				default:
					reqperm = ACL_WR;
					break;
			}

			rte = (RangeTblEntry *) nth(parsetree->resultRelation - 1,
										parsetree->rtable);
			if (!rte->skipAcl)
			{
				acl_rc = pg_aclcheck(rte->relname,
									 GetPgUserName(), reqperm);
				if (acl_rc != ACLCHECK_OK)
				{
					elog(ERROR, "%s: %s",
						 rte->relname,
						 aclcheck_error_strings[acl_rc]);
				}
			}
		}

		/* multiple rule action time */
		*instead_flag = rule_lock->isInstead;
		event_qual = rule_lock->qual;
		actions = rule_lock->actions;
		if (event_qual != NULL && *instead_flag)
		{
			Query	   *qual_product;
			RewriteInfo qual_info;

			/* ----------
			 * If there are instead rules with qualifications,
			 * the original query is still performed. But all
			 * the negated rule qualifications of the instead
			 * rules are added so it does it's actions only
			 * in cases where the rule quals of all instead
			 * rules are false. Think of it as the default
			 * action in a case. We save this in *qual_products
			 * so deepRewriteQuery() can add it to the query
			 * list after we mangled it up enough.
			 * ----------
			 */
			if (*qual_products == NIL)
				qual_product = parsetree;
			else
				qual_product = (Query *) nth(0, *qual_products);

			qual_info.event = qual_product->commandType;
			qual_info.new_varno = length(qual_product->rtable) + 2;
			qual_product = CopyAndAddQual(qual_product,
										  actions,
										  event_qual,
										  rt_index,
										  event);

			qual_info.rule_action = qual_product;

			if (event == CMD_INSERT || event == CMD_UPDATE)
				FixNew(&qual_info, qual_product);

			*qual_products = lappend(NIL, qual_product);
		}

		foreach(r, actions)
		{
			Query	   *rule_action = lfirst(r);
			Node	   *rule_qual = copyObject(event_qual);

			if (rule_action->commandType == CMD_NOTHING)
				continue;

			/*--------------------------------------------------
			 * We copy the qualifications of the parsetree
			 * to the action and vice versa. So force
			 * hasSubLinks if one of them has it.
			 *
			 * As of 6.4 only parsetree qualifications can
			 * have sublinks. If this changes, we must make
			 * this a node lookup at the end of rewriting.
			 *
			 * Jan
			 *--------------------------------------------------
			 */
			if (parsetree->hasSubLinks && !rule_action->hasSubLinks)
			{
				rule_action = copyObject(rule_action);
				rule_action->hasSubLinks = TRUE;
			}
			if (!parsetree->hasSubLinks && rule_action->hasSubLinks)
				parsetree->hasSubLinks = TRUE;

			/*--------------------------------------------------
			 * Step 1:
			 *	  Rewrite current.attribute or current to tuple variable
			 *	  this appears to be done in parser?
			 *--------------------------------------------------
			 */
			info = gatherRewriteMeta(parsetree, rule_action, rule_qual,
									 rt_index, event, instead_flag);

			/* handle escapable cases, or those handled by other code */
			if (info->nothing)
			{
				if (*instead_flag)
					return NIL;
				else
					continue;
			}

			if (info->action == info->event &&
				info->event == CMD_SELECT)
				continue;

			/*
			 * Event Qualification forces copying of parsetree and
			 * splitting into two queries one w/rule_qual, one w/NOT
			 * rule_qual. Also add user query qual onto rule action
			 */
			qual = parsetree->qual;
			AddQual(info->rule_action, qual);

			if (info->rule_qual != NULL)
				AddQual(info->rule_action, info->rule_qual);

			/*--------------------------------------------------
			 * Step 2:
			 *	  Rewrite new.attribute w/ right hand side of target-list
			 *	  entry for appropriate field name in insert/update
			 *--------------------------------------------------
			 */
			if ((info->event == CMD_INSERT) || (info->event == CMD_UPDATE))
				FixNew(info, parsetree);

			/*--------------------------------------------------
			 * Step 3:
			 *	  rewriting due to retrieve rules
			 *--------------------------------------------------
			 */
			info->rule_action->rtable = info->rt;

			/*
			 * ProcessRetrieveQuery(info->rule_action, info->rt,
			 * &orig_instead_flag, TRUE);
			 */

			/*--------------------------------------------------
			 * Step 4
			 *	  Simplify? hey, no algorithm for simplification... let
			 *	  the planner do it.
			 *--------------------------------------------------
			 */
			results = lappend(results, info->rule_action);

			pfree(info);
		}

		/* ----------
		 * If this was an unqualified instead rule,
		 * throw away an eventually saved 'default' parsetree
		 * ----------
		 */
		if (event_qual == NULL && *instead_flag)
			*qual_products = NIL;
	}
	return results;
}



static List *
RewriteQuery(Query *parsetree, bool *instead_flag, List **qual_products)
{
	CmdType		event;
	List	   *product_queries = NIL;
	int			result_relation = 0;
	RangeTblEntry *rt_entry;
	Relation	rt_entry_relation = NULL;
	RuleLock   *rt_entry_locks = NULL;

	Assert(parsetree != NULL);

	event = parsetree->commandType;

	/*
	 * SELECT rules are handled later when we have all the queries that
	 * should get executed
	 */
	if (event == CMD_SELECT)
		return NIL;

	/*
	 * Utilities aren't rewritten at all - why is this here?
	 */
	if (event == CMD_UTILITY)
		return NIL;

	/*
	 * only for a delete may the targetlist be NULL
	 */
	if (event != CMD_DELETE)
		Assert(parsetree->targetList != NULL);

	result_relation = parsetree->resultRelation;

	/*
	 * the statement is an update, insert or delete - fire rules on it.
	 */
	rt_entry = rt_fetch(result_relation, parsetree->rtable);
	rt_entry_relation = heap_openr(rt_entry->relname);
	rt_entry_locks = rt_entry_relation->rd_rules;
	heap_close(rt_entry_relation);

	if (rt_entry_locks != NULL)
	{
		List	   *locks = matchLocks(event, rt_entry_locks, result_relation, parsetree);

		product_queries = fireRules(parsetree,
									result_relation,
									event,
									instead_flag,
									locks,
									qual_products);
	}

	return product_queries;

}


/*
 * to avoid infinite recursion, we restrict the number of times a query
 * can be rewritten. Detecting cycles is left for the reader as an excercise.
 */
#ifndef REWRITE_INVOKE_MAX
#define REWRITE_INVOKE_MAX		10
#endif

static int	numQueryRewriteInvoked = 0;

/*
 * deepRewriteQuery -
 *	  rewrites the query and apply the rules again on the queries rewritten
 */
static List *
deepRewriteQuery(Query *parsetree)
{
	List	   *n;
	List	   *rewritten = NIL;
	List	   *result = NIL;
	bool		instead;
	List	   *qual_products = NIL;



	if (++numQueryRewriteInvoked > REWRITE_INVOKE_MAX)
	{
		elog(ERROR, "query rewritten %d times, may contain cycles",
			 numQueryRewriteInvoked - 1);
	}

	instead = FALSE;
	result = RewriteQuery(parsetree, &instead, &qual_products);

	foreach(n, result)
	{
		Query	   *pt = lfirst(n);
		List	   *newstuff = NIL;

		newstuff = deepRewriteQuery(pt);
		if (newstuff != NIL)
			rewritten = nconc(rewritten, newstuff);
	}

	/* ----------
	 * qual_products are the original query with the negated
	 * rule qualification of an instead rule
	 * ----------
	 */
	if (qual_products != NIL)
		rewritten = nconc(rewritten, qual_products);

	/* ----------
	 * The original query is appended last if not instead
	 * because update and delete rule actions might not do
	 * anything if they are invoked after the update or
	 * delete is performed. The command counter increment
	 * between the query execution makes the deleted (and
	 * maybe the updated) tuples disappear so the scans
	 * for them in the rule actions cannot find them.
	 * ----------
	 */
	if (!instead)
		rewritten = lappend(rewritten, parsetree);

	return rewritten;
}


/*
 * QueryOneRewrite -
 *	  rewrite one query
 */
static List *
QueryRewriteOne(Query *parsetree)
{
	numQueryRewriteInvoked = 0;

	/*
	 * take a deep breath and apply all the rewrite rules - ay
	 */
	return deepRewriteQuery(parsetree);
}


/* ----------
 * RewritePreprocessQuery -
 *	adjust details in the parsetree, the rule system
 *	depends on
 * ----------
 */
static void
RewritePreprocessQuery(Query *parsetree)
{
	/* ----------
	 * if the query has a resultRelation, reassign the
	 * result domain numbers to the attribute numbers in the
	 * target relation. FixNew() depends on it when replacing
	 * *new* references in a rule action by the expressions
	 * from the rewritten query.
	 * resjunk targets are somewhat arbitrarily given a resno of 0;
	 * this is to prevent FixNew() from matching them to var nodes.
	 * ----------
	 */
	if (parsetree->resultRelation > 0)
	{
		RangeTblEntry *rte;
		Relation	rd;
		List	   *tl;

		rte = (RangeTblEntry *) nth(parsetree->resultRelation - 1,
									parsetree->rtable);
		rd = heap_openr(rte->relname);

		foreach(tl, parsetree->targetList)
		{
			TargetEntry *tle = (TargetEntry *) lfirst(tl);

			if (! tle->resdom->resjunk)
				tle->resdom->resno = attnameAttNum(rd, tle->resdom->resname);
			else
				tle->resdom->resno = 0;
		}

		heap_close(rd);
	}
}


/*
 * BasicQueryRewrite -
 *	  rewrite one query via query rewrite system, possibly returning 0
 *	  or many queries
 */
static List *
BasicQueryRewrite(Query *parsetree)
{
	List	   *querylist;
	List	   *results = NIL;
	List	   *l;
	Query	   *query;

	/*
	 * Step 1
	 *
	 * There still seems something broken with the resdom numbers so we
	 * reassign them first.
	 */
	RewritePreprocessQuery(parsetree);

	/*
	 * Step 2
	 *
	 * Apply all non-SELECT rules possibly getting 0 or many queries
	 */
	querylist = QueryRewriteOne(parsetree);

	/*
	 * Step 3
	 *
	 * Apply all the RIR rules on each query
	 */
	foreach(l, querylist)
	{
		query = fireRIRrules((Query *) lfirst(l));

		/*
		 * If the query was marked having aggregates, check if this is
		 * still true after rewriting. This check must get expanded when
		 * someday aggregates can appear somewhere else than in the
		 * targetlist or the having qual.
		 */
		if (query->hasAggs)
			query->hasAggs = checkQueryHasAggs((Node *) (query->targetList))
				| checkQueryHasAggs((Node *) (query->havingQual));
		query->hasSubLinks = checkQueryHasSubLink((Node *) (query->qual))
			| checkQueryHasSubLink((Node *) (query->havingQual));
		results = lappend(results, query);
	}
	return results;
}

/*
 * QueryRewrite -
 *	  Primary entry point to the query rewriter.
 *	  Rewrite one query via query rewrite system, possibly returning 0
 *	  or many queries.
 *
 * NOTE: The code in QueryRewrite was formerly in pg_parse_and_plan(), and was
 * moved here so that it would be invoked during EXPLAIN.  The division of
 * labor between this routine and BasicQueryRewrite is not obviously correct
 * ... at least not to me ... tgl 5/99.
 */
List *
QueryRewrite(Query *parsetree)
{
	List	   *rewritten,
			   *rewritten_item;

	/*
	 * Rewrite Union, Intersect and Except Queries to normal Union Queries
	 * using IN and NOT IN subselects
	 */
	if (parsetree->intersectClause)
		parsetree = Except_Intersect_Rewrite(parsetree);

	/* Rewrite basic queries (retrieve, append, delete, replace) */
	rewritten = BasicQueryRewrite(parsetree);

	/*
	 * Rewrite the UNIONS.
	 */
	foreach(rewritten_item, rewritten)
	{
		Query	   *qry = (Query *) lfirst(rewritten_item);
		List	   *union_result = NIL;
		List	   *union_item;

		foreach(union_item, qry->unionClause)
		{
			union_result = nconc(union_result,
						BasicQueryRewrite((Query *) lfirst(union_item)));
		}
		qry->unionClause = union_result;
	}

	return rewritten;
}

/* This function takes two targetlists as arguments and checks if the
 * targetlists are compatible (i.e. both select for the same number of
 * attributes and the types are compatible */
static void
check_targetlists_are_compatible(List *prev_target, List *current_target)
{
	List	   *tl,
			   *next_target;
	int			prev_len = 0,
				next_len = 0;

	foreach(tl, prev_target)
		if (!((TargetEntry *) lfirst(tl))->resdom->resjunk)
		prev_len++;

	foreach(next_target, current_target)
		if (!((TargetEntry *) lfirst(next_target))->resdom->resjunk)
		next_len++;

	if (prev_len != next_len)
		elog(ERROR, "Each UNION | EXCEPT | INTERSECT query must have the same number of columns.");

	foreach(next_target, current_target)
	{
		Oid			itype;
		Oid			otype;

		otype = ((TargetEntry *) lfirst(prev_target))->resdom->restype;
		itype = ((TargetEntry *) lfirst(next_target))->resdom->restype;

		/* one or both is a NULL column? then don't convert... */
		if (otype == InvalidOid)
		{
			/* propagate a known type forward, if available */
			if (itype != InvalidOid)
				((TargetEntry *) lfirst(prev_target))->resdom->restype = itype;
#ifdef NOT_USED
			else
			{
				((TargetEntry *) lfirst(prev_target))->resdom->restype = UNKNOWNOID;
				((TargetEntry *) lfirst(next_target))->resdom->restype = UNKNOWNOID;
			}
#endif
		}
		else if (itype == InvalidOid)
		{
		}
		/* they don't match in type? then convert... */
		else if (itype != otype)
		{
			Node	   *expr;

			expr = ((TargetEntry *) lfirst(next_target))->expr;
			expr = CoerceTargetExpr(NULL, expr, itype, otype);
			if (expr == NULL)
			{
				elog(ERROR, "Unable to transform %s to %s"
					 "\n\tEach UNION | EXCEPT | INTERSECT clause must have compatible target types",
					 typeidTypeName(itype),
					 typeidTypeName(otype));
			}
			((TargetEntry *) lfirst(next_target))->expr = expr;
			((TargetEntry *) lfirst(next_target))->resdom->restype = otype;
		}

		/* both are UNKNOWN? then evaluate as text... */
		else if (itype == UNKNOWNOID)
		{
			((TargetEntry *) lfirst(next_target))->resdom->restype = TEXTOID;
			((TargetEntry *) lfirst(prev_target))->resdom->restype = TEXTOID;
		}
		prev_target = lnext(prev_target);
	}
}

/* Rewrites UNION INTERSECT and EXCEPT queries to semantiacally equivalent
 * queries that use IN and NOT IN subselects.
 *
 * The operator tree is attached to 'intersectClause' (see rule
 * 'SelectStmt' in gram.y) of the 'parsetree' given as an
 * argument. First we remember some clauses (the sortClause, the
 * unique flag etc.)  Then we translate the operator tree to DNF
 * (disjunctive normal form) by 'cnfify'. (Note that 'cnfify' produces
 * CNF but as we exchanged ANDs with ORs in function A_Expr_to_Expr()
 * earlier we get DNF after exchanging ANDs and ORs again in the
 * result.) Now we create a new query by evaluating the new operator
 * tree which is in DNF now. For every AND we create an entry in the
 * union list and for every OR we create an IN subselect. (NOT IN
 * subselects are created for OR NOT nodes). The first entry of the
 * union list is handed back but before that the remembered clauses
 * (sortClause etc) are attached to the new top Node (Note that the
 * new top Node can differ from the parsetree given as argument because of
 * the translation to DNF. That's why we have to remember the sortClause or
 * unique flag!) */
static Query *
Except_Intersect_Rewrite(Query *parsetree)
{

	SubLink    *n;
	Query	   *result,
			   *intersect_node;
	List	   *elist,
			   *intersect_list = NIL,
			   *intersect,
			   *intersectClause;
	List	   *union_list = NIL,
			   *sortClause;
	List	   *left_expr,
			   *right_expr,
			   *resnames = NIL;
	char	   *op,
			   *uniqueFlag,
			   *into;
	bool		isBinary,
				isPortal,
				isTemp;
	CmdType		commandType = CMD_SELECT;
	List	   *rtable_insert = NIL;

	List	   *prev_target = NIL;

	/*
	 * Remember the Resnames of the given parsetree's targetlist (these
	 * are the resnames of the first Select Statement of the query
	 * formulated by the user and he wants the columns named by these
	 * strings. The transformation to DNF can cause another Select
	 * Statment to be the top one which uses other names for its columns.
	 * Therefore we remeber the original names and attach them to the
	 * targetlist of the new topmost Node at the end of this function
	 */
	foreach(elist, parsetree->targetList)
	{
		TargetEntry *tent = (TargetEntry *) lfirst(elist);

		resnames = lappend(resnames, tent->resdom->resname);
	}

	/*
	 * If the Statement is an INSERT INTO ... (SELECT...) statement using
	 * UNIONs, INTERSECTs or EXCEPTs and the transformation to DNF makes
	 * another Node to the top node we have to transform the new top node
	 * to an INSERT node and the original INSERT node to a SELECT node
	 */
	if (parsetree->commandType == CMD_INSERT)
	{
		parsetree->commandType = CMD_SELECT;
		commandType = CMD_INSERT;
		parsetree->resultRelation = 0;

		/*
		 * The result relation ( = the one to insert into) has to be
		 * attached to the rtable list of the new top node
		 */
		rtable_insert = nth(length(parsetree->rtable) - 1, parsetree->rtable);
	}

	/*
	 * Save some items, to be able to attach them to the resulting top
	 * node at the end of the function
	 */
	sortClause = parsetree->sortClause;
	uniqueFlag = parsetree->uniqueFlag;
	into = parsetree->into;
	isBinary = parsetree->isBinary;
	isPortal = parsetree->isPortal;
	isTemp = parsetree->isTemp;

	/*
	 * The operator tree attached to parsetree->intersectClause is still
	 * 'raw' ( = the leaf nodes are still SelectStmt nodes instead of
	 * Query nodes) So step through the tree and transform the nodes using
	 * parse_analyze().
	 *
	 * The parsetree (given as an argument to Except_Intersect_Rewrite()) has
	 * already been transformed and transforming it again would cause
	 * troubles.  So we give the 'raw' version (of the cooked parsetree)
	 * to the function to prevent an additional transformation. Instead we
	 * hand back the 'cooked' version also given as an argument to
	 * intersect_tree_analyze()
	 */
	intersectClause =
		(List *) intersect_tree_analyze((Node *) parsetree->intersectClause,
								 (Node *) lfirst(parsetree->unionClause),
										(Node *) parsetree);

	/* intersectClause is no longer needed so set it to NIL */
	parsetree->intersectClause = NIL;

	/*
	 * unionClause will be needed later on but the list it delivered is no
	 * longer needed, so set it to NIL
	 */
	parsetree->unionClause = NIL;

	/*
	 * Transform the operator tree to DNF (remember ANDs and ORs have been
	 * exchanged, that's why we get DNF by using cnfify)
	 *
	 * After the call, explicit ANDs are removed and all AND operands are
	 * simply items in the intersectClause list
	 */
	intersectClause = cnfify((Expr *) intersectClause, true);

	/*
	 * For every entry of the intersectClause list we generate one entry
	 * in the union_list
	 */
	foreach(intersect, intersectClause)
	{

		/*
		 * for every OR we create an IN subselect and for every OR NOT we
		 * create a NOT IN subselect, so first extract all the Select
		 * Query nodes from the tree (that contains only OR or OR NOTs any
		 * more because we did a transformation to DNF
		 *
		 * There must be at least one node that is not negated (i.e. just OR
		 * and not OR NOT) and this node will be the first in the list
		 * returned
		 */
		intersect_list = NIL;
		create_intersect_list((Node *) lfirst(intersect), &intersect_list);

		/*
		 * This one will become the Select Query node, all other nodes are
		 * transformed into subselects under this node!
		 */
		intersect_node = (Query *) lfirst(intersect_list);
		intersect_list = lnext(intersect_list);

		/*
		 * Check if all Select Statements use the same number of
		 * attributes and if all corresponding attributes are of the same
		 * type
		 */
		if (prev_target)
			check_targetlists_are_compatible(prev_target, intersect_node->targetList);
		prev_target = intersect_node->targetList;
		/* End of check for corresponding targetlists */

		/*
		 * Transform all nodes remaining into subselects and add them to
		 * the qualifications of the Select Query node
		 */
		while (intersect_list != NIL)
		{

			n = makeNode(SubLink);

			/* Here we got an OR so transform it to an IN subselect */
			if (IsA(lfirst(intersect_list), Query))
			{

				/*
				 * Check if all Select Statements use the same number of
				 * attributes and if all corresponding attributes are of
				 * the same type
				 */
				check_targetlists_are_compatible(prev_target,
						 ((Query *) lfirst(intersect_list))->targetList);
				/* End of check for corresponding targetlists */

				n->subselect = lfirst(intersect_list);
				op = "=";
				n->subLinkType = ANY_SUBLINK;
				n->useor = false;
			}

			/*
			 * Here we got an OR NOT node so transform it to a NOT IN
			 * subselect
			 */
			else
			{

				/*
				 * Check if all Select Statements use the same number of
				 * attributes and if all corresponding attributes are of
				 * the same type
				 */
				check_targetlists_are_compatible(prev_target,
												 ((Query *) lfirst(((Expr *) lfirst(intersect_list))->args))->targetList);
				/* End of check for corresponding targetlists */

				n->subselect = (Node *) lfirst(((Expr *) lfirst(intersect_list))->args);
				op = "<>";
				n->subLinkType = ALL_SUBLINK;
				n->useor = true;
			}

			/*
			 * Prepare the lefthand side of the Sublinks: All the entries
			 * of the targetlist must be (IN) or must not be (NOT IN) the
			 * subselect
			 */
			foreach(elist, intersect_node->targetList)
			{
				Node	   *expr = lfirst(elist);
				TargetEntry *tent = (TargetEntry *) expr;

				n->lefthand = lappend(n->lefthand, tent->expr);
			}

			/*
			 * The first arguments of oper also have to be created for the
			 * sublink (they are the same as the lefthand side!)
			 */
			left_expr = n->lefthand;
			right_expr = ((Query *) (n->subselect))->targetList;

			foreach(elist, left_expr)
			{
				Node	   *lexpr = lfirst(elist);
				Node	   *rexpr = lfirst(right_expr);
				TargetEntry *tent = (TargetEntry *) rexpr;
				Expr	   *op_expr;

				op_expr = make_op(op, lexpr, tent->expr);

				n->oper = lappend(n->oper, op_expr);
				right_expr = lnext(right_expr);
			}

			/*
			 * If the Select Query node has aggregates in use add all the
			 * subselects to the HAVING qual else to the WHERE qual
			 */
			if (intersect_node->hasAggs == false)
				AddQual(intersect_node, (Node *) n);
			else
				AddHavingQual(intersect_node, (Node *) n);

			/* Now we got sublinks */
			intersect_node->hasSubLinks = true;
			intersect_list = lnext(intersect_list);
		}
		intersect_node->intersectClause = NIL;
		union_list = lappend(union_list, intersect_node);
	}

	/* The first entry to union_list is our new top node */
	result = (Query *) lfirst(union_list);
	/* attach the rest to unionClause */
	result->unionClause = lnext(union_list);
	/* Attach all the items remembered in the beginning of the function */
	result->sortClause = sortClause;
	result->uniqueFlag = uniqueFlag;
	result->into = into;
	result->isPortal = isPortal;
	result->isBinary = isBinary;
	result->isTemp = isTemp;

	/*
	 * The relation to insert into is attached to the range table of the
	 * new top node
	 */
	if (commandType == CMD_INSERT)
	{
		result->rtable = lappend(result->rtable, rtable_insert);
		result->resultRelation = length(result->rtable);
		result->commandType = commandType;
	}

	/*
	 * The resnames of the originally first SelectStatement are attached
	 * to the new first SelectStatement
	 */
	foreach(elist, result->targetList)
	{
		TargetEntry *tent = (TargetEntry *) lfirst(elist);

		tent->resdom->resname = lfirst(resnames);
		resnames = lnext(resnames);
	}
	return result;
}

/* Create a list of nodes that are either Query nodes of NOT Expr
 * nodes followed by a Query node. The tree given in ptr contains at
 * least one non negated Query node. This node is attached to the
 * beginning of the list */

static void
create_intersect_list(Node *ptr, List **intersect_list)
{
	List	   *arg;

	if (IsA(ptr, Query))
	{
		/* The non negated node is attached at the beginning (lcons) */
		*intersect_list = lcons(ptr, *intersect_list);
		return;
	}

	if (IsA(ptr, Expr))
	{
		if (((Expr *) ptr)->opType == NOT_EXPR)
		{
			/* negated nodes are appended to the end (lappend) */
			*intersect_list = lappend(*intersect_list, ptr);
			return;
		}
		else
		{
			foreach(arg, ((Expr *) ptr)->args)
				create_intersect_list(lfirst(arg), intersect_list);
			return;
		}
		return;
	}
}

/* The nodes given in 'tree' are still 'raw' so 'cook' them using parse_analyze().
 * The node given in first_select has already been cooked, so don't transform
 * it again but return a pointer to the previously cooked version given in 'parsetree'
 * instead. */
static Node *
intersect_tree_analyze(Node *tree, Node *first_select, Node *parsetree)
{
	Node	   *result = (Node *) NIL;
	List	   *arg;

	if (IsA(tree, SelectStmt))
	{

		/*
		 * If we get to the tree given in first_select return parsetree
		 * instead of performing parse_analyze()
		 */
		if (tree == first_select)
			result = parsetree;
		else
		{
			/* transform the 'raw' nodes to 'cooked' Query nodes */
			List	   *qtree = parse_analyze(lcons(tree, NIL), NULL);

			result = (Node *) lfirst(qtree);
		}
	}

	if (IsA(tree, Expr))
	{
		/* Call recursively for every argument of the node */
		foreach(arg, ((Expr *) tree)->args)
			lfirst(arg) = intersect_tree_analyze(lfirst(arg), first_select, parsetree);
		result = tree;
	}
	return result;
}