text: /*-------------------------------------------------------------------------
   *
   * rewriteHandler.c
   *		Primary module of query rewriter.
   *
   * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   * IDENTIFICATION
   *	  src/backend/rewrite/rewriteHandler.c
   *
   * NOTES
   *	  Some of the terms used in this file are of historic nature: "retrieve"
   *	  was the PostQUEL keyword for what today is SELECT. "RIR" stands for
   *	  "Retrieve-Instead-Retrieve", that is an ON SELECT DO INSTEAD SELECT rule
   *	  (which has to be unconditional and where only one rule can exist on each
   *	  relation).
   *
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include "access/sysattr.h"
  #include "catalog/pg_type.h"
  #include "commands/trigger.h"
  #include "foreign/fdwapi.h"
  #include "nodes/makefuncs.h"
  #include "nodes/nodeFuncs.h"
  #include "parser/analyze.h"
  #include "parser/parse_coerce.h"
  #include "parser/parsetree.h"
  #include "rewrite/rewriteDefine.h"
  #include "rewrite/rewriteHandler.h"
  #include "rewrite/rewriteManip.h"
  #include "rewrite/rowsecurity.h"
  #include "utils/builtins.h"
  #include "utils/lsyscache.h"
  #include "utils/rel.h"
  
  
  /* We use a list of these to detect recursion in RewriteQuery */
  typedef struct rewrite_event
  {
  	Oid			relation;		/* OID of relation having rules */
  	CmdType		event;			/* type of rule being fired */
  } rewrite_event;
  
  typedef struct acquireLocksOnSubLinks_context
  {
  	bool		for_execute;	/* AcquireRewriteLocks' forExecute param */
  } acquireLocksOnSubLinks_context;
  
  static bool acquireLocksOnSubLinks(Node *node,
  					   acquireLocksOnSubLinks_context *context);
  static Query *rewriteRuleAction(Query *parsetree,
  				  Query *rule_action,
  				  Node *rule_qual,
  				  int rt_index,
  				  CmdType event,
  				  bool *returning_flag);
  static List *adjustJoinTreeList(Query *parsetree, bool removert, int rt_index);
  static List *rewriteTargetListIU(List *targetList,
  					CmdType commandType,
  					Relation target_relation,
  					int result_rti,
  					List **attrno_list);
  static TargetEntry *process_matched_tle(TargetEntry *src_tle,
  					TargetEntry *prior_tle,
  					const char *attrName);
  static Node *get_assignment_input(Node *node);
  static void rewriteValuesRTE(RangeTblEntry *rte, Relation target_relation,
  				 List *attrnos);
  static void rewriteTargetListUD(Query *parsetree, RangeTblEntry *target_rte,
  					Relation target_relation);
  static void markQueryForLocking(Query *qry, Node *jtnode,
  					LockClauseStrength strength, LockWaitPolicy waitPolicy,
  					bool pushedDown);
  static List *matchLocks(CmdType event, RuleLock *rulelocks,
  		   int varno, Query *parsetree, bool *hasUpdate);
  static Query *fireRIRrules(Query *parsetree, List *activeRIRs,
  			 bool forUpdatePushedDown);
  static bool view_has_instead_trigger(Relation view, CmdType event);
  static Bitmapset *adjust_view_column_set(Bitmapset *cols, List *targetlist);
  
  
  /*
   * AcquireRewriteLocks -
   *	  Acquire suitable locks on all the relations mentioned in the Query.
   *	  These locks will ensure that the relation schemas don't change under us
   *	  while we are rewriting and planning the query.
   *
   * forExecute indicates that the query is about to be executed.
   * If so, we'll acquire RowExclusiveLock on the query's resultRelation,
   * RowShareLock on any relation accessed FOR [KEY] UPDATE/SHARE, and
   * AccessShareLock on all other relations mentioned.
   *
   * If forExecute is false, AccessShareLock is acquired on all relations.
   * This case is suitable for ruleutils.c, for example, where we only need
   * schema stability and we don't intend to actually modify any relations.
   *
   * forUpdatePushedDown indicates that a pushed-down FOR [KEY] UPDATE/SHARE
   * applies to the current subquery, requiring all rels to be opened with at
   * least RowShareLock.  This should always be false at the top of the
   * recursion.  This flag is ignored if forExecute is false.
   *
   * A secondary purpose of this routine is to fix up JOIN RTE references to
   * dropped columns (see details below).  Because the RTEs are modified in
   * place, it is generally appropriate for the caller of this routine to have
   * first done a copyObject() to make a writable copy of the querytree in the
   * current memory context.
   *
   * This processing can, and for efficiency's sake should, be skipped when the
   * querytree has just been built by the parser: parse analysis already got
   * all the same locks we'd get here, and the parser will have omitted dropped
   * columns from JOINs to begin with.  But we must do this whenever we are
   * dealing with a querytree produced earlier than the current command.
   *
   * About JOINs and dropped columns: although the parser never includes an
   * already-dropped column in a JOIN RTE's alias var list, it is possible for
   * such a list in a stored rule to include references to dropped columns.
   * (If the column is not explicitly referenced anywhere else in the query,
   * the dependency mechanism won't consider it used by the rule and so won't
   * prevent the column drop.)  To support get_rte_attribute_is_dropped(), we
   * replace join alias vars that reference dropped columns with null pointers.
   *
   * (In PostgreSQL 8.0, we did not do this processing but instead had
   * get_rte_attribute_is_dropped() recurse to detect dropped columns in joins.
   * That approach had horrible performance unfortunately; in particular
   * construction of a nested join was O(N^2) in the nesting depth.)
   */
  void
  AcquireRewriteLocks(Query *parsetree,
  					bool forExecute,
  					bool forUpdatePushedDown)
  {
  	ListCell   *l;
  	int			rt_index;
  	acquireLocksOnSubLinks_context context;
  
  	context.for_execute = forExecute;
  
  	/*
  	 * First, process RTEs of the current query level.
  	 */
  	rt_index = 0;
  	foreach(l, parsetree->rtable)
  	{
  		RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
  		Relation	rel;
  		LOCKMODE	lockmode;
  		List	   *newaliasvars;
  		Index		curinputvarno;
  		RangeTblEntry *curinputrte;
  		ListCell   *ll;
  
  		++rt_index;
  		switch (rte->rtekind)
  		{
  			case RTE_RELATION:
  
  				/*
  				 * Grab the appropriate lock type for the relation, and do not
  				 * release it until end of transaction. This protects the
  				 * rewriter and planner against schema changes mid-query.
  				 *
  				 * Assuming forExecute is true, this logic must match what the
  				 * executor will do, else we risk lock-upgrade deadlocks.
  				 */
  				if (!forExecute)
  					lockmode = AccessShareLock;
  				else if (rt_index == parsetree->resultRelation)
  					lockmode = RowExclusiveLock;
  				else if (forUpdatePushedDown ||
  						 get_parse_rowmark(parsetree, rt_index) != NULL)
  					lockmode = RowShareLock;
  				else
  					lockmode = AccessShareLock;
  
  				rel = heap_open(rte->relid, lockmode);
  
  				/*
  				 * While we have the relation open, update the RTE's relkind,
  				 * just in case it changed since this rule was made.
  				 */
  				rte->relkind = rel->rd_rel->relkind;
  
  				heap_close(rel, NoLock);
  				break;
  
  			case RTE_JOIN:
  
  				/*
  				 * Scan the join's alias var list to see if any columns have
  				 * been dropped, and if so replace those Vars with null
  				 * pointers.
  				 *
  				 * Since a join has only two inputs, we can expect to see
  				 * multiple references to the same input RTE; optimize away
  				 * multiple fetches.
  				 */
  				newaliasvars = NIL;
  				curinputvarno = 0;
  				curinputrte = NULL;
  				foreach(ll, rte->joinaliasvars)
  				{
  					Var		   *aliasitem = (Var *) lfirst(ll);
  					Var		   *aliasvar = aliasitem;
  
  					/* Look through any implicit coercion */
  					aliasvar = (Var *) strip_implicit_coercions((Node *) aliasvar);
  
  					/*
  					 * If the list item isn't a simple Var, then it must
  					 * represent a merged column, ie a USING column, and so it
  					 * couldn't possibly be dropped, since it's referenced in
  					 * the join clause.  (Conceivably it could also be a null
  					 * pointer already?  But that's OK too.)
  					 */
  					if (aliasvar && IsA(aliasvar, Var))
  					{
  						/*
  						 * The elements of an alias list have to refer to
  						 * earlier RTEs of the same rtable, because that's the
  						 * order the planner builds things in.  So we already
  						 * processed the referenced RTE, and so it's safe to
  						 * use get_rte_attribute_is_dropped on it. (This might
  						 * not hold after rewriting or planning, but it's OK
  						 * to assume here.)
  						 */
  						Assert(aliasvar->varlevelsup == 0);
  						if (aliasvar->varno != curinputvarno)
  						{
  							curinputvarno = aliasvar->varno;
  							if (curinputvarno >= rt_index)
  								elog(ERROR, "unexpected varno %d in JOIN RTE %d",
  									 curinputvarno, rt_index);
  							curinputrte = rt_fetch(curinputvarno,
  												   parsetree->rtable);
  						}
  						if (get_rte_attribute_is_dropped(curinputrte,
  														 aliasvar->varattno))
  						{
  							/* Replace the join alias item with a NULL */
  							aliasitem = NULL;
  						}
  					}
  					newaliasvars = lappend(newaliasvars, aliasitem);
  				}
  				rte->joinaliasvars = newaliasvars;
  				break;
  
  			case RTE_SUBQUERY:
  
  				/*
  				 * The subquery RTE itself is all right, but we have to
  				 * recurse to process the represented subquery.
  				 */
  				AcquireRewriteLocks(rte->subquery,
  									forExecute,
  									(forUpdatePushedDown ||
  							get_parse_rowmark(parsetree, rt_index) != NULL));
  				break;
  
  			default:
  				/* ignore other types of RTEs */
  				break;
  		}
  	}
  
  	/* Recurse into subqueries in WITH */
  	foreach(l, parsetree->cteList)
  	{
  		CommonTableExpr *cte = (CommonTableExpr *) lfirst(l);
  
  		AcquireRewriteLocks((Query *) cte->ctequery, forExecute, false);
  	}
  
  	/*
  	 * Recurse into sublink subqueries, too.  But we already did the ones in
  	 * the rtable and cteList.
  	 */
  	if (parsetree->hasSubLinks)
  		query_tree_walker(parsetree, acquireLocksOnSubLinks, &context,
  						  QTW_IGNORE_RC_SUBQUERIES);
  }
  
  /*
   * Walker to find sublink subqueries for AcquireRewriteLocks
   */
  static bool
  acquireLocksOnSubLinks(Node *node, acquireLocksOnSubLinks_context *context)
  {
  	if (node == NULL)
  		return false;
  	if (IsA(node, SubLink))
  	{
  		SubLink    *sub = (SubLink *) node;
  
  		/* Do what we came for */
  		AcquireRewriteLocks((Query *) sub->subselect,
  							context->for_execute,
  							false);
  		/* Fall through to process lefthand args of SubLink */
  	}
  
  	/*
  	 * Do NOT recurse into Query nodes, because AcquireRewriteLocks already
  	 * processed subselects of subselects for us.
  	 */
  	return expression_tree_walker(node, acquireLocksOnSubLinks, context);
  }
  
  
  /*
   * rewriteRuleAction -
   *	  Rewrite the rule action with appropriate qualifiers (taken from
   *	  the triggering query).
   *
   * Input arguments:
   *	parsetree - original query
   *	rule_action - one action (query) of a rule
   *	rule_qual - WHERE condition of rule, or NULL if unconditional
   *	rt_index - RT index of result relation in original query
   *	event - type of rule event
   * Output arguments:
   *	*returning_flag - set TRUE if we rewrite RETURNING clause in rule_action
   *					(must be initialized to FALSE)
   * Return value:
   *	rewritten form of rule_action
   */
  static Query *
  rewriteRuleAction(Query *parsetree,
  				  Query *rule_action,
  				  Node *rule_qual,
  				  int rt_index,
  				  CmdType event,
  				  bool *returning_flag)
  {
  	int			current_varno,
  				new_varno;
  	int			rt_length;
  	Query	   *sub_action;
  	Query	  **sub_action_ptr;
  	acquireLocksOnSubLinks_context context;
  
  	context.for_execute = true;
  
  	/*
  	 * Make modifiable copies of rule action and qual (what we're passed are
  	 * the stored versions in the relcache; don't touch 'em!).
  	 */
  	rule_action = (Query *) copyObject(rule_action);
  	rule_qual = (Node *) copyObject(rule_qual);
  
  	/*
  	 * Acquire necessary locks and fix any deleted JOIN RTE entries.
  	 */
  	AcquireRewriteLocks(rule_action, true, false);
  	(void) acquireLocksOnSubLinks(rule_qual, &context);
  
  	current_varno = rt_index;
  	rt_length = list_length(parsetree->rtable);
  	new_varno = PRS2_NEW_VARNO + rt_length;
  
  	/*
  	 * Adjust rule action and qual to offset its varnos, so that we can merge
  	 * its rtable with the main parsetree's rtable.
  	 *
  	 * If the rule action is an INSERT...SELECT, the OLD/NEW rtable entries
  	 * will be in the SELECT part, and we have to modify that rather than the
  	 * top-level INSERT (kluge!).
  	 */
  	sub_action = getInsertSelectQuery(rule_action, &sub_action_ptr);
  
  	OffsetVarNodes((Node *) sub_action, rt_length, 0);
  	OffsetVarNodes(rule_qual, rt_length, 0);
  	/* but references to OLD should point at original rt_index */
  	ChangeVarNodes((Node *) sub_action,
  				   PRS2_OLD_VARNO + rt_length, rt_index, 0);
  	ChangeVarNodes(rule_qual,
  				   PRS2_OLD_VARNO + rt_length, rt_index, 0);
  
  	/*
  	 * Generate expanded rtable consisting of main parsetree's rtable plus
  	 * rule action's rtable; this becomes the complete rtable for the rule
  	 * action.  Some of the entries may be unused after we finish rewriting,
  	 * but we leave them all in place for two reasons:
  	 *
  	 * We'd have a much harder job to adjust the query's varnos if we
  	 * selectively removed RT entries.
  	 *
  	 * If the rule is INSTEAD, then the original query won't be executed at
  	 * all, and so its rtable must be preserved so that the executor will do
  	 * the correct permissions checks on it.
  	 *
  	 * RT entries that are not referenced in the completed jointree will be
  	 * ignored by the planner, so they do not affect query semantics.  But any
  	 * permissions checks specified in them will be applied during executor
  	 * startup (see ExecCheckRTEPerms()).  This allows us to check that the
  	 * caller has, say, insert-permission on a view, when the view is not
  	 * semantically referenced at all in the resulting query.
  	 *
  	 * When a rule is not INSTEAD, the permissions checks done on its copied
  	 * RT entries will be redundant with those done during execution of the
  	 * original query, but we don't bother to treat that case differently.
  	 *
  	 * NOTE: because planner will destructively alter rtable, we must ensure
  	 * that rule action's rtable is separate and shares no substructure with
  	 * the main rtable.  Hence do a deep copy here.
  	 */
  	sub_action->rtable = list_concat((List *) copyObject(parsetree->rtable),
  									 sub_action->rtable);
  
  	/*
  	 * There could have been some SubLinks in parsetree's rtable, in which
  	 * case we'd better mark the sub_action correctly.
  	 */
  	if (parsetree->hasSubLinks && !sub_action->hasSubLinks)
  	{
  		ListCell   *lc;
  
  		foreach(lc, parsetree->rtable)
  		{
  			RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);
  
  			switch (rte->rtekind)
  			{
  				case RTE_RELATION:
  					sub_action->hasSubLinks =
  						checkExprHasSubLink((Node *) rte->tablesample);
  					break;
  				case RTE_FUNCTION:
  					sub_action->hasSubLinks =
  						checkExprHasSubLink((Node *) rte->functions);
  					break;
  				case RTE_VALUES:
  					sub_action->hasSubLinks =
  						checkExprHasSubLink((Node *) rte->values_lists);
  					break;
  				default:
  					/* other RTE types don't contain bare expressions */
  					break;
  			}
  			if (sub_action->hasSubLinks)
  				break;			/* no need to keep scanning rtable */
  		}
  	}
  
  	/*
  	 * Also, we might have absorbed some RTEs with RLS conditions into the
  	 * sub_action.  If so, mark it as hasRowSecurity, whether or not those
  	 * RTEs will be referenced after we finish rewriting.  (Note: currently
  	 * this is a no-op because RLS conditions aren't added till later, but it
  	 * seems like good future-proofing to do this anyway.)
  	 */
  	sub_action->hasRowSecurity |= parsetree->hasRowSecurity;
  
  	/*
  	 * Each rule action's jointree should be the main parsetree's jointree
  	 * plus that rule's jointree, but usually *without* the original rtindex
  	 * that we're replacing (if present, which it won't be for INSERT). Note
  	 * that if the rule action refers to OLD, its jointree will add a
  	 * reference to rt_index.  If the rule action doesn't refer to OLD, but
  	 * either the rule_qual or the user query quals do, then we need to keep
  	 * the original rtindex in the jointree to provide data for the quals.  We
  	 * don't want the original rtindex to be joined twice, however, so avoid
  	 * keeping it if the rule action mentions it.
  	 *
  	 * As above, the action's jointree must not share substructure with the
  	 * main parsetree's.
  	 */
  	if (sub_action->commandType != CMD_UTILITY)
  	{
  		bool		keeporig;
  		List	   *newjointree;
  
  		Assert(sub_action->jointree != NULL);
  		keeporig = (!rangeTableEntry_used((Node *) sub_action->jointree,
  										  rt_index, 0)) &&
  			(rangeTableEntry_used(rule_qual, rt_index, 0) ||
  			 rangeTableEntry_used(parsetree->jointree->quals, rt_index, 0));
  		newjointree = adjustJoinTreeList(parsetree, !keeporig, rt_index);
  		if (newjointree != NIL)
  		{
  			/*
  			 * If sub_action is a setop, manipulating its jointree will do no
  			 * good at all, because the jointree is dummy.  (Perhaps someday
  			 * we could push the joining and quals down to the member
  			 * statements of the setop?)
  			 */
  			if (sub_action->setOperations != NULL)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("conditional UNION/INTERSECT/EXCEPT statements are not implemented")));
  
  			sub_action->jointree->fromlist =
  				list_concat(newjointree, sub_action->jointree->fromlist);
  
  			/*
  			 * There could have been some SubLinks in newjointree, in which
  			 * case we'd better mark the sub_action correctly.
  			 */
  			if (parsetree->hasSubLinks && !sub_action->hasSubLinks)
  				sub_action->hasSubLinks =
  					checkExprHasSubLink((Node *) newjointree);
  		}
  	}
  
  	/*
  	 * If the original query has any CTEs, copy them into the rule action. But
  	 * we don't need them for a utility action.
  	 */
  	if (parsetree->cteList != NIL && sub_action->commandType != CMD_UTILITY)
  	{
  		ListCell   *lc;
  
  		/*
  		 * Annoying implementation restriction: because CTEs are identified by
  		 * name within a cteList, we can't merge a CTE from the original query
  		 * if it has the same name as any CTE in the rule action.
  		 *
  		 * This could possibly be fixed by using some sort of internally
  		 * generated ID, instead of names, to link CTE RTEs to their CTEs.
  		 */
  		foreach(lc, parsetree->cteList)
  		{
  			CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);
  			ListCell   *lc2;
  
  			foreach(lc2, sub_action->cteList)
  			{
  				CommonTableExpr *cte2 = (CommonTableExpr *) lfirst(lc2);
  
  				if (strcmp(cte->ctename, cte2->ctename) == 0)
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  							 errmsg("WITH query name \"%s\" appears in both a rule action and the query being rewritten",
  									cte->ctename)));
  			}
  		}
  
  		/* OK, it's safe to combine the CTE lists */
  		sub_action->cteList = list_concat(sub_action->cteList,
  										  copyObject(parsetree->cteList));
  	}
  
  	/*
  	 * 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
  	 */
  	AddQual(sub_action, rule_qual);
  
  	AddQual(sub_action, parsetree->jointree->quals);
  
  	/*
  	 * Rewrite new.attribute with right hand side of target-list entry for
  	 * appropriate field name in insert/update.
  	 *
  	 * KLUGE ALERT: since ReplaceVarsFromTargetList returns a mutated copy, we
  	 * can't just apply it to sub_action; we have to remember to update the
  	 * sublink inside rule_action, too.
  	 */
  	if ((event == CMD_INSERT || event == CMD_UPDATE) &&
  		sub_action->commandType != CMD_UTILITY)
  	{
  		sub_action = (Query *)
  			ReplaceVarsFromTargetList((Node *) sub_action,
  									  new_varno,
  									  0,
  									  rt_fetch(new_varno, sub_action->rtable),
  									  parsetree->targetList,
  									  (event == CMD_UPDATE) ?
  									  REPLACEVARS_CHANGE_VARNO :
  									  REPLACEVARS_SUBSTITUTE_NULL,
  									  current_varno,
  									  NULL);
  		if (sub_action_ptr)
  			*sub_action_ptr = sub_action;
  		else
  			rule_action = sub_action;
  	}
  
  	/*
  	 * If rule_action has a RETURNING clause, then either throw it away if the
  	 * triggering query has no RETURNING clause, or rewrite it to emit what
  	 * the triggering query's RETURNING clause asks for.  Throw an error if
  	 * more than one rule has a RETURNING clause.
  	 */
  	if (!parsetree->returningList)
  		rule_action->returningList = NIL;
  	else if (rule_action->returningList)
  	{
  		if (*returning_flag)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				   errmsg("cannot have RETURNING lists in multiple rules")));
  		*returning_flag = true;
  		rule_action->returningList = (List *)
  			ReplaceVarsFromTargetList((Node *) parsetree->returningList,
  									  parsetree->resultRelation,
  									  0,
  									  rt_fetch(parsetree->resultRelation,
  											   parsetree->rtable),
  									  rule_action->returningList,
  									  REPLACEVARS_REPORT_ERROR,
  									  0,
  									  &rule_action->hasSubLinks);
  
  		/*
  		 * There could have been some SubLinks in parsetree's returningList,
  		 * in which case we'd better mark the rule_action correctly.
  		 */
  		if (parsetree->hasSubLinks && !rule_action->hasSubLinks)
  			rule_action->hasSubLinks =
  				checkExprHasSubLink((Node *) rule_action->returningList);
  	}
  
  	return rule_action;
  }
  
  /*
   * Copy the query's jointree list, and optionally attempt to remove any
   * occurrence of the given rt_index as a top-level join item (we do not look
   * for it within join items; this is OK because we are only expecting to find
   * it as an UPDATE or DELETE target relation, which will be at the top level
   * of the join).  Returns modified jointree list --- this is a separate copy
   * sharing no nodes with the original.
   */
  static List *
  adjustJoinTreeList(Query *parsetree, bool removert, int rt_index)
  {
  	List	   *newjointree = copyObject(parsetree->jointree->fromlist);
  	ListCell   *l;
  
  	if (removert)
  	{
  		foreach(l, newjointree)
  		{
  			RangeTblRef *rtr = lfirst(l);
  
  			if (IsA(rtr, RangeTblRef) &&
  				rtr->rtindex == rt_index)
  			{
  				newjointree = list_delete_ptr(newjointree, rtr);
  
  				/*
  				 * foreach is safe because we exit loop after list_delete...
  				 */
  				break;
  			}
  		}
  	}
  	return newjointree;
  }
  
  
  /*
   * rewriteTargetListIU - rewrite INSERT/UPDATE targetlist into standard form
   *
   * This has the following responsibilities:
   *
   * 1. For an INSERT, add tlist entries to compute default values for any
   * attributes that have defaults and are not assigned to in the given tlist.
   * (We do not insert anything for default-less attributes, however.  The
   * planner will later insert NULLs for them, but there's no reason to slow
   * down rewriter processing with extra tlist nodes.)  Also, for both INSERT
   * and UPDATE, replace explicit DEFAULT specifications with column default
   * expressions.
   *
   * 2. For an UPDATE on a trigger-updatable view, add tlist entries for any
   * unassigned-to attributes, assigning them their old values.  These will
   * later get expanded to the output values of the view.  (This is equivalent
   * to what the planner's expand_targetlist() will do for UPDATE on a regular
   * table, but it's more convenient to do it here while we still have easy
   * access to the view's original RT index.)  This is only necessary for
   * trigger-updatable views, for which the view remains the result relation of
   * the query.  For auto-updatable views we must not do this, since it might
   * add assignments to non-updatable view columns.  For rule-updatable views it
   * is unnecessary extra work, since the query will be rewritten with a
   * different result relation which will be processed when we recurse via
   * RewriteQuery.
   *
   * 3. Merge multiple entries for the same target attribute, or declare error
   * if we can't.  Multiple entries are only allowed for INSERT/UPDATE of
   * portions of an array or record field, for example
   *			UPDATE table SET foo[2] = 42, foo[4] = 43;
   * We can merge such operations into a single assignment op.  Essentially,
   * the expression we want to produce in this case is like
   *		foo = array_set_element(array_set_element(foo, 2, 42), 4, 43)
   *
   * 4. Sort the tlist into standard order: non-junk fields in order by resno,
   * then junk fields (these in no particular order).
   *
   * We must do items 1,2,3 before firing rewrite rules, else rewritten
   * references to NEW.foo will produce wrong or incomplete results.  Item 4
   * is not needed for rewriting, but will be needed by the planner, and we
   * can do it essentially for free while handling the other items.
   *
   * If attrno_list isn't NULL, we return an additional output besides the
   * rewritten targetlist: an integer list of the assigned-to attnums, in
   * order of the original tlist's non-junk entries.  This is needed for
   * processing VALUES RTEs.
   */
  static List *
  rewriteTargetListIU(List *targetList,
  					CmdType commandType,
  					Relation target_relation,
  					int result_rti,
  					List **attrno_list)
  {
  	TargetEntry **new_tles;
  	List	   *new_tlist = NIL;
  	List	   *junk_tlist = NIL;
  	Form_pg_attribute att_tup;
  	int			attrno,
  				next_junk_attrno,
  				numattrs;
  	ListCell   *temp;
  
  	if (attrno_list)			/* initialize optional result list */
  		*attrno_list = NIL;
  
  	/*
  	 * We process the normal (non-junk) attributes by scanning the input tlist
  	 * once and transferring TLEs into an array, then scanning the array to
  	 * build an output tlist.  This avoids O(N^2) behavior for large numbers
  	 * of attributes.
  	 *
  	 * Junk attributes are tossed into a separate list during the same tlist
  	 * scan, then appended to the reconstructed tlist.
  	 */
  	numattrs = RelationGetNumberOfAttributes(target_relation);
  	new_tles = (TargetEntry **) palloc0(numattrs * sizeof(TargetEntry *));
  	next_junk_attrno = numattrs + 1;
  
  	foreach(temp, targetList)
  	{
  		TargetEntry *old_tle = (TargetEntry *) lfirst(temp);
  
  		if (!old_tle->resjunk)
  		{
  			/* Normal attr: stash it into new_tles[] */
  			attrno = old_tle->resno;
  			if (attrno < 1 || attrno > numattrs)
  				elog(ERROR, "bogus resno %d in targetlist", attrno);
  			att_tup = target_relation->rd_att->attrs[attrno - 1];
  
  			/* put attrno into attrno_list even if it's dropped */
  			if (attrno_list)
  				*attrno_list = lappend_int(*attrno_list, attrno);
  
  			/* We can (and must) ignore deleted attributes */
  			if (att_tup->attisdropped)
  				continue;
  
  			/* Merge with any prior assignment to same attribute */
  			new_tles[attrno - 1] =
  				process_matched_tle(old_tle,
  									new_tles[attrno - 1],
  									NameStr(att_tup->attname));
  		}
  		else
  		{
  			/*
  			 * Copy all resjunk tlist entries to junk_tlist, and assign them
  			 * resnos above the last real resno.
  			 *
  			 * Typical junk entries include ORDER BY or GROUP BY expressions
  			 * (are these actually possible in an INSERT or UPDATE?), system
  			 * attribute references, etc.
  			 */
  
  			/* Get the resno right, but don't copy unnecessarily */
  			if (old_tle->resno != next_junk_attrno)
  			{
  				old_tle = flatCopyTargetEntry(old_tle);
  				old_tle->resno = next_junk_attrno;
  			}
  			junk_tlist = lappend(junk_tlist, old_tle);
  			next_junk_attrno++;
  		}
  	}
  
  	for (attrno = 1; attrno <= numattrs; attrno++)
  	{
  		TargetEntry *new_tle = new_tles[attrno - 1];
  
  		att_tup = target_relation->rd_att->attrs[attrno - 1];
  
  		/* We can (and must) ignore deleted attributes */
  		if (att_tup->attisdropped)
  			continue;
  
  		/*
  		 * Handle the two cases where we need to insert a default expression:
  		 * it's an INSERT and there's no tlist entry for the column, or the
  		 * tlist entry is a DEFAULT placeholder node.
  		 */
  		if ((new_tle == NULL && commandType == CMD_INSERT) ||
  			(new_tle && new_tle->expr && IsA(new_tle->expr, SetToDefault)))
  		{
  			Node	   *new_expr;
  
  			new_expr = build_column_default(target_relation, attrno);
  
  			/*
  			 * If there is no default (ie, default is effectively NULL), we
  			 * can omit the tlist entry in the INSERT case, since the planner
  			 * can insert a NULL for itself, and there's no point in spending
  			 * any more rewriter cycles on the entry.  But in the UPDATE case
  			 * we've got to explicitly set the column to NULL.
  			 */
  			if (!new_expr)
  			{
  				if (commandType == CMD_INSERT)
  					new_tle = NULL;
  				else
  				{
  					new_expr = (Node *) makeConst(att_tup->atttypid,
  												  -1,
  												  att_tup->attcollation,
  												  att_tup->attlen,
  												  (Datum) 0,
  												  true, /* isnull */
  												  att_tup->attbyval);
  					/* this is to catch a NOT NULL domain constraint */
  					new_expr = coerce_to_domain(new_expr,
  												InvalidOid, -1,
  												att_tup->atttypid,
  												COERCE_IMPLICIT_CAST,
  												-1,
  												false,
  												false);
  				}
  			}
  
  			if (new_expr)
  				new_tle = makeTargetEntry((Expr *) new_expr,
  										  attrno,
  										  pstrdup(NameStr(att_tup->attname)),
  										  false);
  		}
  
  		/*
  		 * For an UPDATE on a trigger-updatable view, provide a dummy entry
  		 * whenever there is no explicit assignment.
  		 */
  		if (new_tle == NULL && commandType == CMD_UPDATE &&
  			target_relation->rd_rel->relkind == RELKIND_VIEW &&
  			view_has_instead_trigger(target_relation, CMD_UPDATE))
  		{
  			Node	   *new_expr;
  
  			new_expr = (Node *) makeVar(result_rti,
  										attrno,
  										att_tup->atttypid,
  										att_tup->atttypmod,
  										att_tup->attcollation,
  										0);
  
  			new_tle = makeTargetEntry((Expr *) new_expr,
  									  attrno,
  									  pstrdup(NameStr(att_tup->attname)),
  									  false);
  		}
  
  		if (new_tle)
  			new_tlist = lappend(new_tlist, new_tle);
  	}
  
  	pfree(new_tles);
  
  	return list_concat(new_tlist, junk_tlist);
  }
  
  
  /*
   * Convert a matched TLE from the original tlist into a correct new TLE.
   *
   * This routine detects and handles multiple assignments to the same target
   * attribute.  (The attribute name is needed only for error messages.)
   */
  static TargetEntry *
  process_matched_tle(TargetEntry *src_tle,
  					TargetEntry *prior_tle,
  					const char *attrName)
  {
  	TargetEntry *result;
  	Node	   *src_expr;
  	Node	   *prior_expr;
  	Node	   *src_input;
  	Node	   *prior_input;
  	Node	   *priorbottom;
  	Node	   *newexpr;
  
  	if (prior_tle == NULL)
  	{
  		/*
  		 * Normal case where this is the first assignment to the attribute.
  		 */
  		return src_tle;
  	}
  
  	/*----------
  	 * Multiple assignments to same attribute.  Allow only if all are
  	 * FieldStore or ArrayRef assignment operations.  This is a bit
  	 * tricky because what we may actually be looking at is a nest of
  	 * such nodes; consider
  	 *		UPDATE tab SET col.fld1.subfld1 = x, col.fld2.subfld2 = y
  	 * The two expressions produced by the parser will look like
  	 *		FieldStore(col, fld1, FieldStore(placeholder, subfld1, x))
  	 *		FieldStore(col, fld2, FieldStore(placeholder, subfld2, y))
  	 * However, we can ignore the substructure and just consider the top
  	 * FieldStore or ArrayRef from each assignment, because it works to
  	 * combine these as
  	 *		FieldStore(FieldStore(col, fld1,
  	 *							  FieldStore(placeholder, subfld1, x)),
  	 *				   fld2, FieldStore(placeholder, subfld2, y))
  	 * Note the leftmost expression goes on the inside so that the
  	 * assignments appear to occur left-to-right.
  	 *
  	 * For FieldStore, instead of nesting we can generate a single
  	 * FieldStore with multiple target fields.  We must nest when
  	 * ArrayRefs are involved though.
  	 *----------
  	 */
  	src_expr = (Node *) src_tle->expr;
  	prior_expr = (Node *) prior_tle->expr;
  	src_input = get_assignment_input(src_expr);
  	prior_input = get_assignment_input(prior_expr);
  	if (src_input == NULL ||
  		prior_input == NULL ||
  		exprType(src_expr) != exprType(prior_expr))
  		ereport(ERROR,
  				(errcode(ERRCODE_SYNTAX_ERROR),
  				 errmsg("multiple assignments to same column \"%s\"",
  						attrName)));
  
  	/*
  	 * Prior TLE could be a nest of assignments if we do this more than once.
  	 */
  	priorbottom = prior_input;
  	for (;;)
  	{
  		Node	   *newbottom = get_assignment_input(priorbottom);
  
  		if (newbottom == NULL)
  			break;				/* found the original Var reference */
  		priorbottom = newbottom;
  	}
  	if (!equal(priorbottom, src_input))
  		ereport(ERROR,
  				(errcode(ERRCODE_SYNTAX_ERROR),
  				 errmsg("multiple assignments to same column \"%s\"",
  						attrName)));
  
  	/*
  	 * Looks OK to nest 'em.
  	 */
  	if (IsA(src_expr, FieldStore))
  	{
  		FieldStore *fstore = makeNode(FieldStore);
  
  		if (IsA(prior_expr, FieldStore))
  		{
  			/* combine the two */
  			memcpy(fstore, prior_expr, sizeof(FieldStore));
  			fstore->newvals =
  				list_concat(list_copy(((FieldStore *) prior_expr)->newvals),
  							list_copy(((FieldStore *) src_expr)->newvals));
  			fstore->fieldnums =
  				list_concat(list_copy(((FieldStore *) prior_expr)->fieldnums),
  							list_copy(((FieldStore *) src_expr)->fieldnums));
  		}
  		else
  		{
  			/* general case, just nest 'em */
  			memcpy(fstore, src_expr, sizeof(FieldStore));
  			fstore->arg = (Expr *) prior_expr;
  		}
  		newexpr = (Node *) fstore;
  	}
  	else if (IsA(src_expr, ArrayRef))
  	{
  		ArrayRef   *aref = makeNode(ArrayRef);
  
  		memcpy(aref, src_expr, sizeof(ArrayRef));
  		aref->refexpr = (Expr *) prior_expr;
  		newexpr = (Node *) aref;
  	}
  	else
  	{
  		elog(ERROR, "cannot happen");
  		newexpr = NULL;
  	}
  
  	result = flatCopyTargetEntry(src_tle);
  	result->expr = (Expr *) newexpr;
  	return result;
  }
  
  /*
   * If node is an assignment node, return its input; else return NULL
   */
  static Node *
  get_assignment_input(Node *node)
  {
  	if (node == NULL)
  		return NULL;
  	if (IsA(node, FieldStore))
  	{
  		FieldStore *fstore = (FieldStore *) node;
  
  		return (Node *) fstore->arg;
  	}
  	else if (IsA(node, ArrayRef))
  	{
  		ArrayRef   *aref = (ArrayRef *) node;
  
  		if (aref->refassgnexpr == NULL)
  			return NULL;
  		return (Node *) aref->refexpr;
  	}
  	return NULL;
  }
  
  /*
   * Make an expression tree for the default value for a column.
   *
   * If there is no default, return a NULL instead.
   */
  Node *
  build_column_default(Relation rel, int attrno)
  {
  	TupleDesc	rd_att = rel->rd_att;
  	Form_pg_attribute att_tup = rd_att->attrs[attrno - 1];
  	Oid			atttype = att_tup->atttypid;
  	int32		atttypmod = att_tup->atttypmod;
  	Node	   *expr = NULL;
  	Oid			exprtype;
  
  	/*
  	 * Scan to see if relation has a default for this column.
  	 */
  	if (rd_att->constr && rd_att->constr->num_defval > 0)
  	{
  		AttrDefault *defval = rd_att->constr->defval;
  		int			ndef = rd_att->constr->num_defval;
  
  		while (--ndef >= 0)
  		{
  			if (attrno == defval[ndef].adnum)
  			{
  				/*
  				 * Found it, convert string representation to node tree.
  				 */
  				expr = stringToNode(defval[ndef].adbin);
  				break;
  			}
  		}
  	}
  
  	if (expr == NULL)
  	{
  		/*
  		 * No per-column default, so look for a default for the type itself.
  		 */
  		expr = get_typdefault(atttype);
  	}
  
  	if (expr == NULL)
  		return NULL;			/* No default anywhere */
  
  	/*
  	 * Make sure the value is coerced to the target column type; this will
  	 * generally be true already, but there seem to be some corner cases
  	 * involving domain defaults where it might not be true. This should match
  	 * the parser's processing of non-defaulted expressions --- see
  	 * transformAssignedExpr().
  	 */
  	exprtype = exprType(expr);
  
  	expr = coerce_to_target_type(NULL,	/* no UNKNOWN params here */
  								 expr, exprtype,
  								 atttype, atttypmod,
  								 COERCION_ASSIGNMENT,
  								 COERCE_IMPLICIT_CAST,
  								 -1);
  	if (expr == NULL)
  		ereport(ERROR,
  				(errcode(ERRCODE_DATATYPE_MISMATCH),
  				 errmsg("column \"%s\" is of type %s"
  						" but default expression is of type %s",
  						NameStr(att_tup->attname),
  						format_type_be(atttype),
  						format_type_be(exprtype)),
  			   errhint("You will need to rewrite or cast the expression.")));
  
  	return expr;
  }
  
  
  /* Does VALUES RTE contain any SetToDefault items? */
  static bool
  searchForDefault(RangeTblEntry *rte)
  {
  	ListCell   *lc;
  
  	foreach(lc, rte->values_lists)
  	{
  		List	   *sublist = (List *) lfirst(lc);
  		ListCell   *lc2;
  
  		foreach(lc2, sublist)
  		{
  			Node	   *col = (Node *) lfirst(lc2);
  
  			if (IsA(col, SetToDefault))
  				return true;
  		}
  	}
  	return false;
  }
  
  /*
   * When processing INSERT ... VALUES with a VALUES RTE (ie, multiple VALUES
   * lists), we have to replace any DEFAULT items in the VALUES lists with
   * the appropriate default expressions.  The other aspects of targetlist
   * rewriting need be applied only to the query's targetlist proper.
   *
   * Note that we currently can't support subscripted or field assignment
   * in the multi-VALUES case.  The targetlist will contain simple Vars
   * referencing the VALUES RTE, and therefore process_matched_tle() will
   * reject any such attempt with "multiple assignments to same column".
   */
  static void
  rewriteValuesRTE(RangeTblEntry *rte, Relation target_relation, List *attrnos)
  {
  	List	   *newValues;
  	ListCell   *lc;
  
  	/*
  	 * Rebuilding all the lists is a pretty expensive proposition in a big
  	 * VALUES list, and it's a waste of time if there aren't any DEFAULT
  	 * placeholders.  So first scan to see if there are any.
  	 */
  	if (!searchForDefault(rte))
  		return;					/* nothing to do */
  
  	/* Check list lengths (we can assume all the VALUES sublists are alike) */
  	Assert(list_length(attrnos) == list_length(linitial(rte->values_lists)));
  
  	newValues = NIL;
  	foreach(lc, rte->values_lists)
  	{
  		List	   *sublist = (List *) lfirst(lc);
  		List	   *newList = NIL;
  		ListCell   *lc2;
  		ListCell   *lc3;
  
  		forboth(lc2, sublist, lc3, attrnos)
  		{
  			Node	   *col = (Node *) lfirst(lc2);
  			int			attrno = lfirst_int(lc3);
  
  			if (IsA(col, SetToDefault))
  			{
  				Form_pg_attribute att_tup;
  				Node	   *new_expr;
  
  				att_tup = target_relation->rd_att->attrs[attrno - 1];
  
  				if (!att_tup->attisdropped)
  					new_expr = build_column_default(target_relation, attrno);
  				else
  					new_expr = NULL;	/* force a NULL if dropped */
  
  				/*
  				 * If there is no default (ie, default is effectively NULL),
  				 * we've got to explicitly set the column to NULL.
  				 */
  				if (!new_expr)
  				{
  					new_expr = (Node *) makeConst(att_tup->atttypid,
  												  -1,
  												  att_tup->attcollation,
  												  att_tup->attlen,
  												  (Datum) 0,
  												  true, /* isnull */
  												  att_tup->attbyval);
  					/* this is to catch a NOT NULL domain constraint */
  					new_expr = coerce_to_domain(new_expr,
  												InvalidOid, -1,
  												att_tup->atttypid,
  												COERCE_IMPLICIT_CAST,
  												-1,
  												false,
  												false);
  				}
  				newList = lappend(newList, new_expr);
  			}
  			else
  				newList = lappend(newList, col);
  		}
  		newValues = lappend(newValues, newList);
  	}
  	rte->values_lists = newValues;
  }
  
  
  /*
   * rewriteTargetListUD - rewrite UPDATE/DELETE targetlist as needed
   *
   * This function adds a "junk" TLE that is needed to allow the executor to
   * find the original row for the update or delete.  When the target relation
   * is a regular table, the junk TLE emits the ctid attribute of the original
   * row.  When the target relation is a view, there is no ctid, so we instead
   * emit a whole-row Var that will contain the "old" values of the view row.
   * If it's a foreign table, we let the FDW decide what to add.
   *
   * For UPDATE queries, this is applied after rewriteTargetListIU.  The
   * ordering isn't actually critical at the moment.
   */
  static void
  rewriteTargetListUD(Query *parsetree, RangeTblEntry *target_rte,
  					Relation target_relation)
  {
  	Var		   *var = NULL;
  	const char *attrname;
  	TargetEntry *tle;
  
  	if (target_relation->rd_rel->relkind == RELKIND_RELATION ||
  		target_relation->rd_rel->relkind == RELKIND_MATVIEW ||
  		target_relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  	{
  		/*
  		 * Emit CTID so that executor can find the row to update or delete.
  		 */
  		var = makeVar(parsetree->resultRelation,
  					  SelfItemPointerAttributeNumber,
  					  TIDOID,
  					  -1,
  					  InvalidOid,
  					  0);
  
  		attrname = "ctid";
  	}
  	else if (target_relation->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
  	{
  		/*
  		 * Let the foreign table's FDW add whatever junk TLEs it wants.
  		 */
  		FdwRoutine *fdwroutine;
  
  		fdwroutine = GetFdwRoutineForRelation(target_relation, false);
  
  		if (fdwroutine->AddForeignUpdateTargets != NULL)
  			fdwroutine->AddForeignUpdateTargets(parsetree, target_rte,
  												target_relation);
  
  		/*
  		 * If we have a row-level trigger corresponding to the operation, emit
  		 * a whole-row Var so that executor will have the "old" row to pass to
  		 * the trigger.  Alas, this misses system columns.
  		 */
  		if (target_relation->trigdesc &&
  			((parsetree->commandType == CMD_UPDATE &&
  			  (target_relation->trigdesc->trig_update_after_row ||
  			   target_relation->trigdesc->trig_update_before_row)) ||
  			 (parsetree->commandType == CMD_DELETE &&
  			  (target_relation->trigdesc->trig_delete_after_row ||
  			   target_relation->trigdesc->trig_delete_before_row))))
  		{
  			var = makeWholeRowVar(target_rte,
  								  parsetree->resultRelation,
  								  0,
  								  false);
  
  			attrname = "wholerow";
  		}
  	}
  	else
  	{
  		/*
  		 * Emit whole-row Var so that executor will have the "old" view row to
  		 * pass to the INSTEAD OF trigger.
  		 */
  		var = makeWholeRowVar(target_rte,
  							  parsetree->resultRelation,
  							  0,
  							  false);
  
  		attrname = "wholerow";
  	}
  
  	if (var != NULL)
  	{
  		tle = makeTargetEntry((Expr *) var,
  							  list_length(parsetree->targetList) + 1,
  							  pstrdup(attrname),
  							  true);
  
  		parsetree->targetList = lappend(parsetree->targetList, tle);
  	}
  }
  
  
  /*
   * matchLocks -
   *	  match the list of locks and returns the matching rules
   */
  static List *
  matchLocks(CmdType event,
  		   RuleLock *rulelocks,
  		   int varno,
  		   Query *parsetree,
  		   bool *hasUpdate)
  {
  	List	   *matching_locks = NIL;
  	int			nlocks;
  	int			i;
  
  	if (rulelocks == NULL)
  		return NIL;
  
  	if (parsetree->commandType != CMD_SELECT)
  	{
  		if (parsetree->resultRelation != varno)
  			return NIL;
  	}
  
  	nlocks = rulelocks->numLocks;
  
  	for (i = 0; i < nlocks; i++)
  	{
  		RewriteRule *oneLock = rulelocks->rules[i];
  
  		if (oneLock->event == CMD_UPDATE)
  			*hasUpdate = true;
  
  		/*
  		 * Suppress ON INSERT/UPDATE/DELETE rules that are disabled or
  		 * configured to not fire during the current sessions replication
  		 * role. ON SELECT rules will always be applied in order to keep views
  		 * working even in LOCAL or REPLICA role.
  		 */
  		if (oneLock->event != CMD_SELECT)
  		{
  			if (SessionReplicationRole == SESSION_REPLICATION_ROLE_REPLICA)
  			{
  				if (oneLock->enabled == RULE_FIRES_ON_ORIGIN ||
  					oneLock->enabled == RULE_DISABLED)
  					continue;
  			}
  			else	/* ORIGIN or LOCAL ROLE */
  			{
  				if (oneLock->enabled == RULE_FIRES_ON_REPLICA ||
  					oneLock->enabled == RULE_DISABLED)
  					continue;
  			}
  		}
  
  		if (oneLock->event == event)
  		{
  			if (parsetree->commandType != CMD_SELECT ||
  				rangeTableEntry_used((Node *) parsetree, varno, 0))
  				matching_locks = lappend(matching_locks, oneLock);
  		}
  	}
  
  	return matching_locks;
  }
  
  
  /*
   * ApplyRetrieveRule - expand an ON SELECT rule
   */
  static Query *
  ApplyRetrieveRule(Query *parsetree,
  				  RewriteRule *rule,
  				  int rt_index,
  				  Relation relation,
  				  List *activeRIRs,
  				  bool forUpdatePushedDown)
  {
  	Query	   *rule_action;
  	RangeTblEntry *rte,
  			   *subrte;
  	RowMarkClause *rc;
  
  	if (list_length(rule->actions) != 1)
  		elog(ERROR, "expected just one rule action");
  	if (rule->qual != NULL)
  		elog(ERROR, "cannot handle qualified ON SELECT rule");
  
  	if (rt_index == parsetree->resultRelation)
  	{
  		/*
  		 * We have a view as the result relation of the query, and it wasn't
  		 * rewritten by any rule.  This case is supported if there is an
  		 * INSTEAD OF trigger that will trap attempts to insert/update/delete
  		 * view rows.  The executor will check that; for the moment just plow
  		 * ahead.  We have two cases:
  		 *
  		 * For INSERT, we needn't do anything.  The unmodified RTE will serve
  		 * fine as the result relation.
  		 *
  		 * For UPDATE/DELETE, we need to expand the view so as to have source
  		 * data for the operation.  But we also need an unmodified RTE to
  		 * serve as the target.  So, copy the RTE and add the copy to the
  		 * rangetable.  Note that the copy does not get added to the jointree.
  		 * Also note that there's a hack in fireRIRrules to avoid calling this
  		 * function again when it arrives at the copied RTE.
  		 */
  		if (parsetree->commandType == CMD_INSERT)
  			return parsetree;
  		else if (parsetree->commandType == CMD_UPDATE ||
  				 parsetree->commandType == CMD_DELETE)
  		{
  			RangeTblEntry *newrte;
  
  			rte = rt_fetch(rt_index, parsetree->rtable);
  			newrte = copyObject(rte);
  			parsetree->rtable = lappend(parsetree->rtable, newrte);
  			parsetree->resultRelation = list_length(parsetree->rtable);
  
  			/*
  			 * There's no need to do permissions checks twice, so wipe out the
  			 * permissions info for the original RTE (we prefer to keep the
  			 * bits set on the result RTE).
  			 */
  			rte->requiredPerms = 0;
  			rte->checkAsUser = InvalidOid;
  			rte->selectedCols = NULL;
  			rte->insertedCols = NULL;
  			rte->updatedCols = NULL;
  
  			/*
  			 * For the most part, Vars referencing the view should remain as
  			 * they are, meaning that they implicitly represent OLD values.
  			 * But in the RETURNING list if any, we want such Vars to
  			 * represent NEW values, so change them to reference the new RTE.
  			 *
  			 * Since ChangeVarNodes scribbles on the tree in-place, copy the
  			 * RETURNING list first for safety.
  			 */
  			parsetree->returningList = copyObject(parsetree->returningList);
  			ChangeVarNodes((Node *) parsetree->returningList, rt_index,
  						   parsetree->resultRelation, 0);
  
  			/* Now, continue with expanding the original view RTE */
  		}
  		else
  			elog(ERROR, "unrecognized commandType: %d",
  				 (int) parsetree->commandType);
  	}
  
  	/*
  	 * If FOR [KEY] UPDATE/SHARE of view, be sure we get right initial lock on
  	 * the relations it references.
  	 */
  	rc = get_parse_rowmark(parsetree, rt_index);
  	forUpdatePushedDown |= (rc != NULL);
  
  	/*
  	 * Make a modifiable copy of the view query, and acquire needed locks on
  	 * the relations it mentions.
  	 */
  	rule_action = copyObject(linitial(rule->actions));
  
  	AcquireRewriteLocks(rule_action, true, forUpdatePushedDown);
  
  	/*
  	 * Recursively expand any view references inside the view.
  	 */
  	rule_action = fireRIRrules(rule_action, activeRIRs, forUpdatePushedDown);
  
  	/*
  	 * Now, plug the view query in as a subselect, replacing the relation's
  	 * original RTE.
  	 */
  	rte = rt_fetch(rt_index, parsetree->rtable);
  
  	rte->rtekind = RTE_SUBQUERY;
  	rte->relid = InvalidOid;
  	rte->security_barrier = RelationIsSecurityView(relation);
  	rte->subquery = rule_action;
  	rte->inh = false;			/* must not be set for a subquery */
  
  	/*
  	 * We move the view's permission check data down to its rangetable. The
  	 * checks will actually be done against the OLD entry therein.
  	 */
  	subrte = rt_fetch(PRS2_OLD_VARNO, rule_action->rtable);
  	Assert(subrte->relid == relation->rd_id);
  	subrte->requiredPerms = rte->requiredPerms;
  	subrte->checkAsUser = rte->checkAsUser;
  	subrte->selectedCols = rte->selectedCols;
  	subrte->insertedCols = rte->insertedCols;
  	subrte->updatedCols = rte->updatedCols;
  
  	rte->requiredPerms = 0;		/* no permission check on subquery itself */
  	rte->checkAsUser = InvalidOid;
  	rte->selectedCols = NULL;
  	rte->insertedCols = NULL;
  	rte->updatedCols = NULL;
  
  	/*
  	 * If FOR [KEY] UPDATE/SHARE of view, mark all the contained tables as
  	 * implicit FOR [KEY] UPDATE/SHARE, the same as the parser would have done
  	 * if the view's subquery had been written out explicitly.
  	 *
  	 * Note: we don't consider forUpdatePushedDown here; such marks will be
  	 * made by recursing from the upper level in markQueryForLocking.
  	 */
  	if (rc != NULL)
  		markQueryForLocking(rule_action, (Node *) rule_action->jointree,
  							rc->strength, rc->waitPolicy, true);
  
  	return parsetree;
  }
  
  /*
   * Recursively mark all relations used by a view as FOR [KEY] UPDATE/SHARE.
   *
   * This may generate an invalid query, eg if some sub-query uses an
   * aggregate.  We leave it to the planner to detect that.
   *
   * NB: this must agree with the parser's transformLockingClause() routine.
   * However, unlike the parser we have to be careful not to mark a view's
   * OLD and NEW rels for updating.  The best way to handle that seems to be
   * to scan the jointree to determine which rels are used.
   */
  static void
  markQueryForLocking(Query *qry, Node *jtnode,
  					LockClauseStrength strength, LockWaitPolicy waitPolicy,
  					bool pushedDown)
  {
  	if (jtnode == NULL)
  		return;
  	if (IsA(jtnode, RangeTblRef))
  	{
  		int			rti = ((RangeTblRef *) jtnode)->rtindex;
  		RangeTblEntry *rte = rt_fetch(rti, qry->rtable);
  
  		if (rte->rtekind == RTE_RELATION)
  		{
  			applyLockingClause(qry, rti, strength, waitPolicy, pushedDown);
  			rte->requiredPerms |= ACL_SELECT_FOR_UPDATE;
  		}
  		else if (rte->rtekind == RTE_SUBQUERY)
  		{
  			applyLockingClause(qry, rti, strength, waitPolicy, pushedDown);
  			/* FOR UPDATE/SHARE of subquery is propagated to subquery's rels */
  			markQueryForLocking(rte->subquery, (Node *) rte->subquery->jointree,
  								strength, waitPolicy, true);
  		}
  		/* other RTE types are unaffected by FOR UPDATE */
  	}
  	else if (IsA(jtnode, FromExpr))
  	{
  		FromExpr   *f = (FromExpr *) jtnode;
  		ListCell   *l;
  
  		foreach(l, f->fromlist)
  			markQueryForLocking(qry, lfirst(l), strength, waitPolicy, pushedDown);
  	}
  	else if (IsA(jtnode, JoinExpr))
  	{
  		JoinExpr   *j = (JoinExpr *) jtnode;
  
  		markQueryForLocking(qry, j->larg, strength, waitPolicy, pushedDown);
  		markQueryForLocking(qry, j->rarg, strength, waitPolicy, pushedDown);
  	}
  	else
  		elog(ERROR, "unrecognized node type: %d",
  			 (int) nodeTag(jtnode));
  }
  
  
  /*
   * fireRIRonSubLink -
   *	Apply fireRIRrules() to each SubLink (subselect in expression) found
   *	in the given tree.
   *
   * NOTE: although this has the form of a walker, we cheat and modify the
   * SubLink nodes in-place.  It is caller's responsibility to ensure that
   * no unwanted side-effects occur!
   *
   * This is unlike most of the other routines that recurse into subselects,
   * because we must take control at the SubLink node in order to replace
   * the SubLink's subselect link with the possibly-rewritten subquery.
   */
  static bool
  fireRIRonSubLink(Node *node, List *activeRIRs)
  {
  	if (node == NULL)
  		return false;
  	if (IsA(node, SubLink))
  	{
  		SubLink    *sub = (SubLink *) node;
  
  		/* Do what we came for */
  		sub->subselect = (Node *) fireRIRrules((Query *) sub->subselect,
  											   activeRIRs, false);
  		/* Fall through to process lefthand args of SubLink */
  	}
  
  	/*
  	 * Do NOT recurse into Query nodes, because fireRIRrules already processed
  	 * subselects of subselects for us.
  	 */
  	return expression_tree_walker(node, fireRIRonSubLink,
  								  (void *) activeRIRs);
  }
  
  
  /*
   * fireRIRrules -
   *	Apply all RIR rules on each rangetable entry in a query
   */
  static Query *
  fireRIRrules(Query *parsetree, List *activeRIRs, bool forUpdatePushedDown)
  {
  	int			origResultRelation = parsetree->resultRelation;
  	int			rt_index;
  	ListCell   *lc;
  
  	/*
  	 * don't try to convert this into a foreach loop, because rtable list can
  	 * get changed each time through...
  	 */
  	rt_index = 0;
  	while (rt_index < list_length(parsetree->rtable))
  	{
  		RangeTblEntry *rte;
  		Relation	rel;
  		List	   *locks;
  		RuleLock   *rules;
  		RewriteRule *rule;
  		int			i;
  
  		++rt_index;
  
  		rte = rt_fetch(rt_index, parsetree->rtable);
  
  		/*
  		 * A subquery RTE can't have associated rules, so there's nothing to
  		 * do to this level of the query, but we must recurse into the
  		 * subquery to expand any rule references in it.
  		 */
  		if (rte->rtekind == RTE_SUBQUERY)
  		{
  			rte->subquery = fireRIRrules(rte->subquery, activeRIRs,
  										 (forUpdatePushedDown ||
  							get_parse_rowmark(parsetree, rt_index) != NULL));
  			continue;
  		}
  
  		/*
  		 * Joins and other non-relation RTEs can be ignored completely.
  		 */
  		if (rte->rtekind != RTE_RELATION)
  			continue;
  
  		/*
  		 * Always ignore RIR rules for materialized views referenced in
  		 * queries.  (This does not prevent refreshing MVs, since they aren't
  		 * referenced in their own query definitions.)
  		 *
  		 * Note: in the future we might want to allow MVs to be conditionally
  		 * expanded as if they were regular views, if they are not scannable.
  		 * In that case this test would need to be postponed till after we've
  		 * opened the rel, so that we could check its state.
  		 */
  		if (rte->relkind == RELKIND_MATVIEW)
  			continue;
  
  		/*
  		 * If the table is not referenced in the query, then we ignore it.
  		 * This prevents infinite expansion loop due to new rtable entries
  		 * inserted by expansion of a rule. A table is referenced if it is
  		 * part of the join set (a source table), or is referenced by any Var
  		 * nodes, or is the result table.
  		 */
  		if (rt_index != parsetree->resultRelation &&
  			!rangeTableEntry_used((Node *) parsetree, rt_index, 0))
  			continue;
  
  		/*
  		 * Also, if this is a new result relation introduced by
  		 * ApplyRetrieveRule, we don't want to do anything more with it.
  		 */
  		if (rt_index == parsetree->resultRelation &&
  			rt_index != origResultRelation)
  			continue;
  
  		/*
  		 * We can use NoLock here since either the parser or
  		 * AcquireRewriteLocks should have locked the rel already.
  		 */
  		rel = heap_open(rte->relid, NoLock);
  
  		/*
  		 * Collect the RIR rules that we must apply
  		 */
  		rules = rel->rd_rules;
  		if (rules != NULL)
  		{
  			locks = NIL;
  			for (i = 0; i < rules->numLocks; i++)
  			{
  				rule = rules->rules[i];
  				if (rule->event != CMD_SELECT)
  					continue;
  
  				locks = lappend(locks, rule);
  			}
  
  			/*
  			 * If we found any, apply them --- but first check for recursion!
  			 */
  			if (locks != NIL)
  			{
  				ListCell   *l;
  
  				if (list_member_oid(activeRIRs, RelationGetRelid(rel)))
  					ereport(ERROR,
  							(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  							 errmsg("infinite recursion detected in rules for relation \"%s\"",
  									RelationGetRelationName(rel))));
  				activeRIRs = lcons_oid(RelationGetRelid(rel), activeRIRs);
  
  				foreach(l, locks)
  				{
  					rule = lfirst(l);
  
  					parsetree = ApplyRetrieveRule(parsetree,
  												  rule,
  												  rt_index,
  												  rel,
  												  activeRIRs,
  												  forUpdatePushedDown);
  				}
  
  				activeRIRs = list_delete_first(activeRIRs);
  			}
  		}
  
  		heap_close(rel, NoLock);
  	}
  
  	/* Recurse into subqueries in WITH */
  	foreach(lc, parsetree->cteList)
  	{
  		CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);
  
  		cte->ctequery = (Node *)
  			fireRIRrules((Query *) cte->ctequery, activeRIRs, false);
  	}
  
  	/*
  	 * Recurse into sublink subqueries, too.  But we already did the ones in
  	 * the rtable and cteList.
  	 */
  	if (parsetree->hasSubLinks)
  		query_tree_walker(parsetree, fireRIRonSubLink, (void *) activeRIRs,
  						  QTW_IGNORE_RC_SUBQUERIES);
  
  	/*
  	 * Apply any row level security policies.  We do this last because it
  	 * requires special recursion detection if the new quals have sublink
  	 * subqueries, and if we did it in the loop above query_tree_walker would
  	 * then recurse into those quals a second time.
  	 */
  	rt_index = 0;
  	foreach(lc, parsetree->rtable)
  	{
  		RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);
  		Relation	rel;
  		List	   *securityQuals;
  		List	   *withCheckOptions;
  		bool		hasRowSecurity;
  		bool		hasSubLinks;
  
  		++rt_index;
  
  		/* Only normal relations can have RLS policies */
  		if (rte->rtekind != RTE_RELATION ||
  			rte->relkind != RELKIND_RELATION)
  			continue;
  
  		rel = heap_open(rte->relid, NoLock);
  
  		/*
  		 * Fetch any new security quals that must be applied to this RTE.
  		 */
  		get_row_security_policies(parsetree, rte, rt_index,
  								  &securityQuals, &withCheckOptions,
  								  &hasRowSecurity, &hasSubLinks);
  
  		if (securityQuals != NIL || withCheckOptions != NIL)
  		{
  			if (hasSubLinks)
  			{
  				acquireLocksOnSubLinks_context context;
  
  				/*
  				 * Recursively process the new quals, checking for infinite
  				 * recursion.
  				 */
  				if (list_member_oid(activeRIRs, RelationGetRelid(rel)))
  					ereport(ERROR,
  							(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  							 errmsg("infinite recursion detected in policy for relation \"%s\"",
  									RelationGetRelationName(rel))));
  
  				activeRIRs = lcons_oid(RelationGetRelid(rel), activeRIRs);
  
  				/*
  				 * get_row_security_policies just passed back securityQuals
  				 * and/or withCheckOptions, and there were SubLinks, make sure
  				 * we lock any relations which are referenced.
  				 *
  				 * These locks would normally be acquired by the parser, but
  				 * securityQuals and withCheckOptions are added post-parsing.
  				 */
  				context.for_execute = true;
  				(void) acquireLocksOnSubLinks((Node *) securityQuals, &context);
  				(void) acquireLocksOnSubLinks((Node *) withCheckOptions,
  											  &context);
  
  				/*
  				 * Now that we have the locks on anything added by
  				 * get_row_security_policies, fire any RIR rules for them.
  				 */
  				expression_tree_walker((Node *) securityQuals,
  									   fireRIRonSubLink, (void *) activeRIRs);
  
  				expression_tree_walker((Node *) withCheckOptions,
  									   fireRIRonSubLink, (void *) activeRIRs);
  
  				activeRIRs = list_delete_first(activeRIRs);
  			}
  
  			/*
  			 * Add the new security barrier quals to the start of the RTE's
  			 * list so that they get applied before any existing barrier quals
  			 * (which would have come from a security-barrier view, and should
  			 * get lower priority than RLS conditions on the table itself).
  			 */
  			rte->securityQuals = list_concat(securityQuals,
  											 rte->securityQuals);
  
  			parsetree->withCheckOptions = list_concat(withCheckOptions,
  												parsetree->withCheckOptions);
  		}
  
  		/*
  		 * Make sure the query is marked correctly if row level security
  		 * applies, or if the new quals had sublinks.
  		 */
  		if (hasRowSecurity)
  			parsetree->hasRowSecurity = true;
  		if (hasSubLinks)
  			parsetree->hasSubLinks = true;
  
  		heap_close(rel, NoLock);
  	}
  
  	return parsetree;
  }
  
  
  /*
   * Modify the given query by adding 'AND rule_qual IS NOT TRUE' to its
   * qualification.  This is used to generate suitable "else clauses" for
   * conditional INSTEAD rules.  (Unfortunately we must use "x IS NOT TRUE",
   * not just "NOT x" which the planner is much smarter about, else we will
   * do the wrong thing when the qual evaluates to NULL.)
   *
   * The rule_qual may contain references to OLD or NEW.  OLD references are
   * replaced by references to the specified rt_index (the relation that the
   * rule applies to).  NEW references are only possible for INSERT and UPDATE
   * queries on the relation itself, and so they should be replaced by copies
   * of the related entries in the query's own targetlist.
   */
  static Query *
  CopyAndAddInvertedQual(Query *parsetree,
  					   Node *rule_qual,
  					   int rt_index,
  					   CmdType event)
  {
  	/* Don't scribble on the passed qual (it's in the relcache!) */
  	Node	   *new_qual = (Node *) copyObject(rule_qual);
  	acquireLocksOnSubLinks_context context;
  
  	context.for_execute = true;
  
  	/*
  	 * In case there are subqueries in the qual, acquire necessary locks and
  	 * fix any deleted JOIN RTE entries.  (This is somewhat redundant with
  	 * rewriteRuleAction, but not entirely ... consider restructuring so that
  	 * we only need to process the qual this way once.)
  	 */
  	(void) acquireLocksOnSubLinks(new_qual, &context);
  
  	/* Fix references to OLD */
  	ChangeVarNodes(new_qual, PRS2_OLD_VARNO, rt_index, 0);
  	/* Fix references to NEW */
  	if (event == CMD_INSERT || event == CMD_UPDATE)
  		new_qual = ReplaceVarsFromTargetList(new_qual,
  											 PRS2_NEW_VARNO,
  											 0,
  											 rt_fetch(rt_index,
  													  parsetree->rtable),
  											 parsetree->targetList,
  											 (event == CMD_UPDATE) ?
  											 REPLACEVARS_CHANGE_VARNO :
  											 REPLACEVARS_SUBSTITUTE_NULL,
  											 rt_index,
  											 &parsetree->hasSubLinks);
  	/* And attach the fixed qual */
  	AddInvertedQual(parsetree, new_qual);
  
  	return parsetree;
  }
  
  
  /*
   *	fireRules -
   *	   Iterate through rule locks applying rules.
   *
   * Input arguments:
   *	parsetree - original query
   *	rt_index - RT index of result relation in original query
   *	event - type of rule event
   *	locks - list of rules to fire
   * Output arguments:
   *	*instead_flag - set TRUE if any unqualified INSTEAD rule is found
   *					(must be initialized to FALSE)
   *	*returning_flag - set TRUE if we rewrite RETURNING clause in any rule
   *					(must be initialized to FALSE)
   *	*qual_product - filled with modified original query if any qualified
   *					INSTEAD rule is found (must be initialized to NULL)
   * Return value:
   *	list of rule actions adjusted for use with this query
   *
   * Qualified INSTEAD rules generate their action with the qualification
   * condition added.  They also generate a modified version of the original
   * query with the negated qualification added, so that it will run only for
   * rows that the qualified action doesn't act on.  (If there are multiple
   * qualified INSTEAD rules, we AND all the negated quals onto a single
   * modified original query.)  We won't execute the original, unmodified
   * query if we find either qualified or unqualified INSTEAD rules.  If
   * we find both, the modified original query is discarded too.
   */
  static List *
  fireRules(Query *parsetree,
  		  int rt_index,
  		  CmdType event,
  		  List *locks,
  		  bool *instead_flag,
  		  bool *returning_flag,
  		  Query **qual_product)
  {
  	List	   *results = NIL;
  	ListCell   *l;
  
  	foreach(l, locks)
  	{
  		RewriteRule *rule_lock = (RewriteRule *) lfirst(l);
  		Node	   *event_qual = rule_lock->qual;
  		List	   *actions = rule_lock->actions;
  		QuerySource qsrc;
  		ListCell   *r;
  
  		/* Determine correct QuerySource value for actions */
  		if (rule_lock->isInstead)
  		{
  			if (event_qual != NULL)
  				qsrc = QSRC_QUAL_INSTEAD_RULE;
  			else
  			{
  				qsrc = QSRC_INSTEAD_RULE;
  				*instead_flag = true;	/* report unqualified INSTEAD */
  			}
  		}
  		else
  			qsrc = QSRC_NON_INSTEAD_RULE;
  
  		if (qsrc == QSRC_QUAL_INSTEAD_RULE)
  		{
  			/*
  			 * 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 its
  			 * 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_product so RewriteQuery() can add it to the query
  			 * list after we mangled it up enough.
  			 *
  			 * If we have already found an unqualified INSTEAD rule, then
  			 * *qual_product won't be used, so don't bother building it.
  			 */
  			if (!*instead_flag)
  			{
  				if (*qual_product == NULL)
  					*qual_product = copyObject(parsetree);
  				*qual_product = CopyAndAddInvertedQual(*qual_product,
  													   event_qual,
  													   rt_index,
  													   event);
  			}
  		}
  
  		/* Now process the rule's actions and add them to the result list */
  		foreach(r, actions)
  		{
  			Query	   *rule_action = lfirst(r);
  
  			if (rule_action->commandType == CMD_NOTHING)
  				continue;
  
  			rule_action = rewriteRuleAction(parsetree, rule_action,
  											event_qual, rt_index, event,
  											returning_flag);
  
  			rule_action->querySource = qsrc;
  			rule_action->canSetTag = false;		/* might change later */
  
  			results = lappend(results, rule_action);
  		}
  	}
  
  	return results;
  }
  
  
  /*
   * get_view_query - get the Query from a view's _RETURN rule.
   *
   * Caller should have verified that the relation is a view, and therefore
   * we should find an ON SELECT action.
   *
   * Note that the pointer returned is into the relcache and therefore must
   * be treated as read-only to the caller and not modified or scribbled on.
   */
  Query *
  get_view_query(Relation view)
  {
  	int			i;
  
  	Assert(view->rd_rel->relkind == RELKIND_VIEW);
  
  	for (i = 0; i < view->rd_rules->numLocks; i++)
  	{
  		RewriteRule *rule = view->rd_rules->rules[i];
  
  		if (rule->event == CMD_SELECT)
  		{
  			/* A _RETURN rule should have only one action */
  			if (list_length(rule->actions) != 1)
  				elog(ERROR, "invalid _RETURN rule action specification");
  
  			return (Query *) linitial(rule->actions);
  		}
  	}
  
  	elog(ERROR, "failed to find _RETURN rule for view");
  	return NULL;				/* keep compiler quiet */
  }
  
  
  /*
   * view_has_instead_trigger - does view have an INSTEAD OF trigger for event?
   *
   * If it does, we don't want to treat it as auto-updatable.  This test can't
   * be folded into view_query_is_auto_updatable because it's not an error
   * condition.
   */
  static bool
  view_has_instead_trigger(Relation view, CmdType event)
  {
  	TriggerDesc *trigDesc = view->trigdesc;
  
  	switch (event)
  	{
  		case CMD_INSERT:
  			if (trigDesc && trigDesc->trig_insert_instead_row)
  				return true;
  			break;
  		case CMD_UPDATE:
  			if (trigDesc && trigDesc->trig_update_instead_row)
  				return true;
  			break;
  		case CMD_DELETE:
  			if (trigDesc && trigDesc->trig_delete_instead_row)
  				return true;
  			break;
  		default:
  			elog(ERROR, "unrecognized CmdType: %d", (int) event);
  			break;
  	}
  	return false;
  }
  
  
  /*
   * view_col_is_auto_updatable - test whether the specified column of a view
   * is auto-updatable. Returns NULL (if the column can be updated) or a message
   * string giving the reason that it cannot be.
   *
   * Note that the checks performed here are local to this view. We do not check
   * whether the referenced column of the underlying base relation is updatable.
   */
  static const char *
  view_col_is_auto_updatable(RangeTblRef *rtr, TargetEntry *tle)
  {
  	Var		   *var = (Var *) tle->expr;
  
  	/*
  	 * For now, the only updatable columns we support are those that are Vars
  	 * referring to user columns of the underlying base relation.
  	 *
  	 * The view targetlist may contain resjunk columns (e.g., a view defined
  	 * like "SELECT * FROM t ORDER BY a+b" is auto-updatable) but such columns
  	 * are not auto-updatable, and in fact should never appear in the outer
  	 * query's targetlist.
  	 */
  	if (tle->resjunk)
  		return gettext_noop("Junk view columns are not updatable.");
  
  	if (!IsA(var, Var) ||
  		var->varno != rtr->rtindex ||
  		var->varlevelsup != 0)
  		return gettext_noop("View columns that are not columns of their base relation are not updatable.");
  
  	if (var->varattno < 0)
  		return gettext_noop("View columns that refer to system columns are not updatable.");
  
  	if (var->varattno == 0)
  		return gettext_noop("View columns that return whole-row references are not updatable.");
  
  	return NULL;				/* the view column is updatable */
  }
  
  
  /*
   * view_query_is_auto_updatable - test whether the specified view definition
   * represents an auto-updatable view. Returns NULL (if the view can be updated)
   * or a message string giving the reason that it cannot be.
   *
   * If check_cols is true, the view is required to have at least one updatable
   * column (necessary for INSERT/UPDATE). Otherwise the view's columns are not
   * checked for updatability. See also view_cols_are_auto_updatable.
   *
   * Note that the checks performed here are only based on the view definition.
   * We do not check whether any base relations referred to by the view are
   * updatable.
   */
  const char *
  view_query_is_auto_updatable(Query *viewquery, bool check_cols)
  {
  	RangeTblRef *rtr;
  	RangeTblEntry *base_rte;
  
  	/*----------
  	 * Check if the view is simply updatable.  According to SQL-92 this means:
  	 *	- No DISTINCT clause.
  	 *	- Each TLE is a column reference, and each column appears at most once.
  	 *	- FROM contains exactly one base relation.
  	 *	- No GROUP BY or HAVING clauses.
  	 *	- No set operations (UNION, INTERSECT or EXCEPT).
  	 *	- No sub-queries in the WHERE clause that reference the target table.
  	 *
  	 * We ignore that last restriction since it would be complex to enforce
  	 * and there isn't any actual benefit to disallowing sub-queries.  (The
  	 * semantic issues that the standard is presumably concerned about don't
  	 * arise in Postgres, since any such sub-query will not see any updates
  	 * executed by the outer query anyway, thanks to MVCC snapshotting.)
  	 *
  	 * We also relax the second restriction by supporting part of SQL:1999
  	 * feature T111, which allows for a mix of updatable and non-updatable
  	 * columns, provided that an INSERT or UPDATE doesn't attempt to assign to
  	 * a non-updatable column.
  	 *
  	 * In addition we impose these constraints, involving features that are
  	 * not part of SQL-92:
  	 *	- No CTEs (WITH clauses).
  	 *	- No OFFSET or LIMIT clauses (this matches a SQL:2008 restriction).
  	 *	- No system columns (including whole-row references) in the tlist.
  	 *	- No window functions in the tlist.
  	 *	- No set-returning functions in the tlist.
  	 *
  	 * Note that we do these checks without recursively expanding the view.
  	 * If the base relation is a view, we'll recursively deal with it later.
  	 *----------
  	 */
  	if (viewquery->distinctClause != NIL)
  		return gettext_noop("Views containing DISTINCT are not automatically updatable.");
  
  	if (viewquery->groupClause != NIL || viewquery->groupingSets)
  		return gettext_noop("Views containing GROUP BY are not automatically updatable.");
  
  	if (viewquery->havingQual != NULL)
  		return gettext_noop("Views containing HAVING are not automatically updatable.");
  
  	if (viewquery->setOperations != NULL)
  		return gettext_noop("Views containing UNION, INTERSECT, or EXCEPT are not automatically updatable.");
  
  	if (viewquery->cteList != NIL)
  		return gettext_noop("Views containing WITH are not automatically updatable.");
  
  	if (viewquery->limitOffset != NULL || viewquery->limitCount != NULL)
  		return gettext_noop("Views containing LIMIT or OFFSET are not automatically updatable.");
  
  	/*
  	 * We must not allow window functions or set returning functions in the
  	 * targetlist. Otherwise we might end up inserting them into the quals of
  	 * the main query. We must also check for aggregates in the targetlist in
  	 * case they appear without a GROUP BY.
  	 *
  	 * These restrictions ensure that each row of the view corresponds to a
  	 * unique row in the underlying base relation.
  	 */
  	if (viewquery->hasAggs)
  		return gettext_noop("Views that return aggregate functions are not automatically updatable.");
  
  	if (viewquery->hasWindowFuncs)
  		return gettext_noop("Views that return window functions are not automatically updatable.");
  
  	if (viewquery->hasTargetSRFs)
  		return gettext_noop("Views that return set-returning functions are not automatically updatable.");
  
  	/*
  	 * The view query should select from a single base relation, which must be
  	 * a table or another view.
  	 */
  	if (list_length(viewquery->jointree->fromlist) != 1)
  		return gettext_noop("Views that do not select from a single table or view are not automatically updatable.");
  
  	rtr = (RangeTblRef *) linitial(viewquery->jointree->fromlist);
  	if (!IsA(rtr, RangeTblRef))
  		return gettext_noop("Views that do not select from a single table or view are not automatically updatable.");
  
  	base_rte = rt_fetch(rtr->rtindex, viewquery->rtable);
  	if (base_rte->rtekind != RTE_RELATION ||
  		(base_rte->relkind != RELKIND_RELATION &&
  		 base_rte->relkind != RELKIND_FOREIGN_TABLE &&
  		 base_rte->relkind != RELKIND_VIEW))
  		return gettext_noop("Views that do not select from a single table or view are not automatically updatable.");
  
  	if (base_rte->tablesample)
  		return gettext_noop("Views containing TABLESAMPLE are not automatically updatable.");
  
  	/*
  	 * Check that the view has at least one updatable column. This is required
  	 * for INSERT/UPDATE but not for DELETE.
  	 */
  	if (check_cols)
  	{
  		ListCell   *cell;
  		bool		found;
  
  		found = false;
  		foreach(cell, viewquery->targetList)
  		{
  			TargetEntry *tle = (TargetEntry *) lfirst(cell);
  
  			if (view_col_is_auto_updatable(rtr, tle) == NULL)
  			{
  				found = true;
  				break;
  			}
  		}
  
  		if (!found)
  			return gettext_noop("Views that have no updatable columns are not automatically updatable.");
  	}
  
  	return NULL;				/* the view is updatable */
  }
  
  
  /*
   * view_cols_are_auto_updatable - test whether all of the required columns of
   * an auto-updatable view are actually updatable. Returns NULL (if all the
   * required columns can be updated) or a message string giving the reason that
   * they cannot be.
   *
   * This should be used for INSERT/UPDATE to ensure that we don't attempt to
   * assign to any non-updatable columns.
   *
   * Additionally it may be used to retrieve the set of updatable columns in the
   * view, or if one or more of the required columns is not updatable, the name
   * of the first offending non-updatable column.
   *
   * The caller must have already verified that this is an auto-updatable view
   * using view_query_is_auto_updatable.
   *
   * Note that the checks performed here are only based on the view definition.
   * We do not check whether the referenced columns of the base relation are
   * updatable.
   */
  static const char *
  view_cols_are_auto_updatable(Query *viewquery,
  							 Bitmapset *required_cols,
  							 Bitmapset **updatable_cols,
  							 char **non_updatable_col)
  {
  	RangeTblRef *rtr;
  	AttrNumber	col;
  	ListCell   *cell;
  
  	/*
  	 * The caller should have verified that this view is auto-updatable and so
  	 * there should be a single base relation.
  	 */
  	Assert(list_length(viewquery->jointree->fromlist) == 1);
  	rtr = (RangeTblRef *) linitial(viewquery->jointree->fromlist);
  	Assert(IsA(rtr, RangeTblRef));
  
  	/* Initialize the optional return values */
  	if (updatable_cols != NULL)
  		*updatable_cols = NULL;
  	if (non_updatable_col != NULL)
  		*non_updatable_col = NULL;
  
  	/* Test each view column for updatability */
  	col = -FirstLowInvalidHeapAttributeNumber;
  	foreach(cell, viewquery->targetList)
  	{
  		TargetEntry *tle = (TargetEntry *) lfirst(cell);
  		const char *col_update_detail;
  
  		col++;
  		col_update_detail = view_col_is_auto_updatable(rtr, tle);
  
  		if (col_update_detail == NULL)
  		{
  			/* The column is updatable */
  			if (updatable_cols != NULL)
  				*updatable_cols = bms_add_member(*updatable_cols, col);
  		}
  		else if (bms_is_member(col, required_cols))
  		{
  			/* The required column is not updatable */
  			if (non_updatable_col != NULL)
  				*non_updatable_col = tle->resname;
  			return col_update_detail;
  		}
  	}
  
  	return NULL;				/* all the required view columns are updatable */
  }
  
  
  /*
   * relation_is_updatable - determine which update events the specified
   * relation supports.
   *
   * Note that views may contain a mix of updatable and non-updatable columns.
   * For a view to support INSERT/UPDATE it must have at least one updatable
   * column, but there is no such restriction for DELETE. If include_cols is
   * non-NULL, then only the specified columns are considered when testing for
   * updatability.
   *
   * This is used for the information_schema views, which have separate concepts
   * of "updatable" and "trigger updatable".  A relation is "updatable" if it
   * can be updated without the need for triggers (either because it has a
   * suitable RULE, or because it is simple enough to be automatically updated).
   * A relation is "trigger updatable" if it has a suitable INSTEAD OF trigger.
   * The SQL standard regards this as not necessarily updatable, presumably
   * because there is no way of knowing what the trigger will actually do.
   * The information_schema views therefore call this function with
   * include_triggers = false.  However, other callers might only care whether
   * data-modifying SQL will work, so they can pass include_triggers = true
   * to have trigger updatability included in the result.
   *
   * The return value is a bitmask of rule event numbers indicating which of
   * the INSERT, UPDATE and DELETE operations are supported.  (We do it this way
   * so that we can test for UPDATE plus DELETE support in a single call.)
   */
  int
  relation_is_updatable(Oid reloid,
  					  bool include_triggers,
  					  Bitmapset *include_cols)
  {
  	int			events = 0;
  	Relation	rel;
  	RuleLock   *rulelocks;
  
  #define ALL_EVENTS ((1 << CMD_INSERT) | (1 << CMD_UPDATE) | (1 << CMD_DELETE))
  
  	rel = try_relation_open(reloid, AccessShareLock);
  
  	/*
  	 * If the relation doesn't exist, return zero rather than throwing an
  	 * error.  This is helpful since scanning an information_schema view under
  	 * MVCC rules can result in referencing rels that have actually been
  	 * deleted already.
  	 */
  	if (rel == NULL)
  		return 0;
  
  	/* If the relation is a table, it is always updatable */
  	if (rel->rd_rel->relkind == RELKIND_RELATION)
  	{
  		relation_close(rel, AccessShareLock);
  		return ALL_EVENTS;
  	}
  
  	/* Look for unconditional DO INSTEAD rules, and note supported events */
  	rulelocks = rel->rd_rules;
  	if (rulelocks != NULL)
  	{
  		int			i;
  
  		for (i = 0; i < rulelocks->numLocks; i++)
  		{
  			if (rulelocks->rules[i]->isInstead &&
  				rulelocks->rules[i]->qual == NULL)
  			{
  				events |= ((1 << rulelocks->rules[i]->event) & ALL_EVENTS);
  			}
  		}
  
  		/* If we have rules for all events, we're done */
  		if (events == ALL_EVENTS)
  		{
  			relation_close(rel, AccessShareLock);
  			return events;
  		}
  	}
  
  	/* Similarly look for INSTEAD OF triggers, if they are to be included */
  	if (include_triggers)
  	{
  		TriggerDesc *trigDesc = rel->trigdesc;
  
  		if (trigDesc)
  		{
  			if (trigDesc->trig_insert_instead_row)
  				events |= (1 << CMD_INSERT);
  			if (trigDesc->trig_update_instead_row)
  				events |= (1 << CMD_UPDATE);
  			if (trigDesc->trig_delete_instead_row)
  				events |= (1 << CMD_DELETE);
  
  			/* If we have triggers for all events, we're done */
  			if (events == ALL_EVENTS)
  			{
  				relation_close(rel, AccessShareLock);
  				return events;
  			}
  		}
  	}
  
  	/* If this is a foreign table, check which update events it supports */
  	if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
  	{
  		FdwRoutine *fdwroutine = GetFdwRoutineForRelation(rel, false);
  
  		if (fdwroutine->IsForeignRelUpdatable != NULL)
  			events |= fdwroutine->IsForeignRelUpdatable(rel);
  		else
  		{
  			/* Assume presence of executor functions is sufficient */
  			if (fdwroutine->ExecForeignInsert != NULL)
  				events |= (1 << CMD_INSERT);
  			if (fdwroutine->ExecForeignUpdate != NULL)
  				events |= (1 << CMD_UPDATE);
  			if (fdwroutine->ExecForeignDelete != NULL)
  				events |= (1 << CMD_DELETE);
  		}
  
  		relation_close(rel, AccessShareLock);
  		return events;
  	}
  
  	/* Check if this is an automatically updatable view */
  	if (rel->rd_rel->relkind == RELKIND_VIEW)
  	{
  		Query	   *viewquery = get_view_query(rel);
  
  		if (view_query_is_auto_updatable(viewquery, false) == NULL)
  		{
  			Bitmapset  *updatable_cols;
  			int			auto_events;
  			RangeTblRef *rtr;
  			RangeTblEntry *base_rte;
  			Oid			baseoid;
  
  			/*
  			 * Determine which of the view's columns are updatable. If there
  			 * are none within the set of columns we are looking at, then the
  			 * view doesn't support INSERT/UPDATE, but it may still support
  			 * DELETE.
  			 */
  			view_cols_are_auto_updatable(viewquery, NULL,
  										 &updatable_cols, NULL);
  
  			if (include_cols != NULL)
  				updatable_cols = bms_int_members(updatable_cols, include_cols);
  
  			if (bms_is_empty(updatable_cols))
  				auto_events = (1 << CMD_DELETE);		/* May support DELETE */
  			else
  				auto_events = ALL_EVENTS;		/* May support all events */
  
  			/*
  			 * The base relation must also support these update commands.
  			 * Tables are always updatable, but for any other kind of base
  			 * relation we must do a recursive check limited to the columns
  			 * referenced by the locally updatable columns in this view.
  			 */
  			rtr = (RangeTblRef *) linitial(viewquery->jointree->fromlist);
  			base_rte = rt_fetch(rtr->rtindex, viewquery->rtable);
  			Assert(base_rte->rtekind == RTE_RELATION);
  
  			if (base_rte->relkind != RELKIND_RELATION)
  			{
  				baseoid = base_rte->relid;
  				include_cols = adjust_view_column_set(updatable_cols,
  													  viewquery->targetList);
  				auto_events &= relation_is_updatable(baseoid,
  													 include_triggers,
  													 include_cols);
  			}
  			events |= auto_events;
  		}
  	}
  
  	/* If we reach here, the relation may support some update commands */
  	relation_close(rel, AccessShareLock);
  	return events;
  }
  
  
  /*
   * adjust_view_column_set - map a set of column numbers according to targetlist
   *
   * This is used with simply-updatable views to map column-permissions sets for
   * the view columns onto the matching columns in the underlying base relation.
   * The targetlist is expected to be a list of plain Vars of the underlying
   * relation (as per the checks above in view_query_is_auto_updatable).
   */
  static Bitmapset *
  adjust_view_column_set(Bitmapset *cols, List *targetlist)
  {
  	Bitmapset  *result = NULL;
  	int			col;
  
  	col = -1;
  	while ((col = bms_next_member(cols, col)) >= 0)
  	{
  		/* bit numbers are offset by FirstLowInvalidHeapAttributeNumber */
  		AttrNumber	attno = col + FirstLowInvalidHeapAttributeNumber;
  
  		if (attno == InvalidAttrNumber)
  		{
  			/*
  			 * There's a whole-row reference to the view.  For permissions
  			 * purposes, treat it as a reference to each column available from
  			 * the view.  (We should *not* convert this to a whole-row
  			 * reference to the base relation, since the view may not touch
  			 * all columns of the base relation.)
  			 */
  			ListCell   *lc;
  
  			foreach(lc, targetlist)
  			{
  				TargetEntry *tle = (TargetEntry *) lfirst(lc);
  				Var		   *var;
  
  				if (tle->resjunk)
  					continue;
  				var = (Var *) tle->expr;
  				Assert(IsA(var, Var));
  				result = bms_add_member(result,
  						 var->varattno - FirstLowInvalidHeapAttributeNumber);
  			}
  		}
  		else
  		{
  			/*
  			 * Views do not have system columns, so we do not expect to see
  			 * any other system attnos here.  If we do find one, the error
  			 * case will apply.
  			 */
  			TargetEntry *tle = get_tle_by_resno(targetlist, attno);
  
  			if (tle != NULL && !tle->resjunk && IsA(tle->expr, Var))
  			{
  				Var		   *var = (Var *) tle->expr;
  
  				result = bms_add_member(result,
  						 var->varattno - FirstLowInvalidHeapAttributeNumber);
  			}
  			else
  				elog(ERROR, "attribute number %d not found in view targetlist",
  					 attno);
  		}
  	}
  
  	return result;
  }
  
  
  /*
   * rewriteTargetView -
   *	  Attempt to rewrite a query where the target relation is a view, so that
   *	  the view's base relation becomes the target relation.
   *
   * Note that the base relation here may itself be a view, which may or may not
   * have INSTEAD OF triggers or rules to handle the update.  That is handled by
   * the recursion in RewriteQuery.
   */
  static Query *
  rewriteTargetView(Query *parsetree, Relation view)
  {
  	Query	   *viewquery;
  	const char *auto_update_detail;
  	RangeTblRef *rtr;
  	int			base_rt_index;
  	int			new_rt_index;
  	RangeTblEntry *base_rte;
  	RangeTblEntry *view_rte;
  	RangeTblEntry *new_rte;
  	Relation	base_rel;
  	List	   *view_targetlist;
  	ListCell   *lc;
  
  	/*
  	 * Get the Query from the view's ON SELECT rule.  We're going to munge the
  	 * Query to change the view's base relation into the target relation,
  	 * along with various other changes along the way, so we need to make a
  	 * copy of it (get_view_query() returns a pointer into the relcache, so we
  	 * have to treat it as read-only).
  	 */
  	viewquery = copyObject(get_view_query(view));
  
  	/* The view must be updatable, else fail */
  	auto_update_detail =
  		view_query_is_auto_updatable(viewquery,
  									 parsetree->commandType != CMD_DELETE);
  
  	if (auto_update_detail)
  	{
  		/* messages here should match execMain.c's CheckValidResultRel */
  		switch (parsetree->commandType)
  		{
  			case CMD_INSERT:
  				ereport(ERROR,
  						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  						 errmsg("cannot insert into view \"%s\"",
  								RelationGetRelationName(view)),
  						 errdetail_internal("%s", _(auto_update_detail)),
  						 errhint("To enable inserting into the view, provide an INSTEAD OF INSERT trigger or an unconditional ON INSERT DO INSTEAD rule.")));
  				break;
  			case CMD_UPDATE:
  				ereport(ERROR,
  						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  						 errmsg("cannot update view \"%s\"",
  								RelationGetRelationName(view)),
  						 errdetail_internal("%s", _(auto_update_detail)),
  						 errhint("To enable updating the view, provide an INSTEAD OF UPDATE trigger or an unconditional ON UPDATE DO INSTEAD rule.")));
  				break;
  			case CMD_DELETE:
  				ereport(ERROR,
  						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  						 errmsg("cannot delete from view \"%s\"",
  								RelationGetRelationName(view)),
  						 errdetail_internal("%s", _(auto_update_detail)),
  						 errhint("To enable deleting from the view, provide an INSTEAD OF DELETE trigger or an unconditional ON DELETE DO INSTEAD rule.")));
  				break;
  			default:
  				elog(ERROR, "unrecognized CmdType: %d",
  					 (int) parsetree->commandType);
  				break;
  		}
  	}
  
  	/*
  	 * For INSERT/UPDATE the modified columns must all be updatable. Note that
  	 * we get the modified columns from the query's targetlist, not from the
  	 * result RTE's insertedCols and/or updatedCols set, since
  	 * rewriteTargetListIU may have added additional targetlist entries for
  	 * view defaults, and these must also be updatable.
  	 */
  	if (parsetree->commandType != CMD_DELETE)
  	{
  		Bitmapset  *modified_cols = NULL;
  		char	   *non_updatable_col;
  
  		foreach(lc, parsetree->targetList)
  		{
  			TargetEntry *tle = (TargetEntry *) lfirst(lc);
  
  			if (!tle->resjunk)
  				modified_cols = bms_add_member(modified_cols,
  							tle->resno - FirstLowInvalidHeapAttributeNumber);
  		}
  
  		if (parsetree->onConflict)
  		{
  			foreach(lc, parsetree->onConflict->onConflictSet)
  			{
  				TargetEntry *tle = (TargetEntry *) lfirst(lc);
  
  				if (!tle->resjunk)
  					modified_cols = bms_add_member(modified_cols,
  							tle->resno - FirstLowInvalidHeapAttributeNumber);
  			}
  		}
  
  		auto_update_detail = view_cols_are_auto_updatable(viewquery,
  														  modified_cols,
  														  NULL,
  														  &non_updatable_col);
  		if (auto_update_detail)
  		{
  			/*
  			 * This is a different error, caused by an attempt to update a
  			 * non-updatable column in an otherwise updatable view.
  			 */
  			switch (parsetree->commandType)
  			{
  				case CMD_INSERT:
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					errmsg("cannot insert into column \"%s\" of view \"%s\"",
  						   non_updatable_col,
  						   RelationGetRelationName(view)),
  						   errdetail_internal("%s", _(auto_update_detail))));
  					break;
  				case CMD_UPDATE:
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot update column \"%s\" of view \"%s\"",
  								non_updatable_col,
  								RelationGetRelationName(view)),
  						   errdetail_internal("%s", _(auto_update_detail))));
  					break;
  				default:
  					elog(ERROR, "unrecognized CmdType: %d",
  						 (int) parsetree->commandType);
  					break;
  			}
  		}
  	}
  
  	/* Locate RTE describing the view in the outer query */
  	view_rte = rt_fetch(parsetree->resultRelation, parsetree->rtable);
  
  	/*
  	 * If we get here, view_query_is_auto_updatable() has verified that the
  	 * view contains a single base relation.
  	 */
  	Assert(list_length(viewquery->jointree->fromlist) == 1);
  	rtr = (RangeTblRef *) linitial(viewquery->jointree->fromlist);
  	Assert(IsA(rtr, RangeTblRef));
  
  	base_rt_index = rtr->rtindex;
  	base_rte = rt_fetch(base_rt_index, viewquery->rtable);
  	Assert(base_rte->rtekind == RTE_RELATION);
  
  	/*
  	 * Up to now, the base relation hasn't been touched at all in our query.
  	 * We need to acquire lock on it before we try to do anything with it.
  	 * (The subsequent recursive call of RewriteQuery will suppose that we
  	 * already have the right lock!)  Since it will become the query target
  	 * relation, RowExclusiveLock is always the right thing.
  	 */
  	base_rel = heap_open(base_rte->relid, RowExclusiveLock);
  
  	/*
  	 * While we have the relation open, update the RTE's relkind, just in case
  	 * it changed since this view was made (cf. AcquireRewriteLocks).
  	 */
  	base_rte->relkind = base_rel->rd_rel->relkind;
  
  	heap_close(base_rel, NoLock);
  
  	/*
  	 * If the view query contains any sublink subqueries then we need to also
  	 * acquire locks on any relations they refer to.  We know that there won't
  	 * be any subqueries in the range table or CTEs, so we can skip those, as
  	 * in AcquireRewriteLocks.
  	 */
  	if (viewquery->hasSubLinks)
  	{
  		acquireLocksOnSubLinks_context context;
  
  		context.for_execute = true;
  		query_tree_walker(viewquery, acquireLocksOnSubLinks, &context,
  						  QTW_IGNORE_RC_SUBQUERIES);
  	}
  
  	/*
  	 * Create a new target RTE describing the base relation, and add it to the
  	 * outer query's rangetable.  (What's happening in the next few steps is
  	 * very much like what the planner would do to "pull up" the view into the
  	 * outer query.  Perhaps someday we should refactor things enough so that
  	 * we can share code with the planner.)
  	 */
  	new_rte = (RangeTblEntry *) base_rte;
  	parsetree->rtable = lappend(parsetree->rtable, new_rte);
  	new_rt_index = list_length(parsetree->rtable);
  
  	/*
  	 * INSERTs never inherit.  For UPDATE/DELETE, we use the view query's
  	 * inheritance flag for the base relation.
  	 */
  	if (parsetree->commandType == CMD_INSERT)
  		new_rte->inh = false;
  
  	/*
  	 * Adjust the view's targetlist Vars to reference the new target RTE, ie
  	 * make their varnos be new_rt_index instead of base_rt_index.  There can
  	 * be no Vars for other rels in the tlist, so this is sufficient to pull
  	 * up the tlist expressions for use in the outer query.  The tlist will
  	 * provide the replacement expressions used by ReplaceVarsFromTargetList
  	 * below.
  	 */
  	view_targetlist = viewquery->targetList;
  
  	ChangeVarNodes((Node *) view_targetlist,
  				   base_rt_index,
  				   new_rt_index,
  				   0);
  
  	/*
  	 * Mark the new target RTE for the permissions checks that we want to
  	 * enforce against the view owner, as distinct from the query caller.  At
  	 * the relation level, require the same INSERT/UPDATE/DELETE permissions
  	 * that the query caller needs against the view.  We drop the ACL_SELECT
  	 * bit that is presumably in new_rte->requiredPerms initially.
  	 *
  	 * Note: the original view RTE remains in the query's rangetable list.
  	 * Although it will be unused in the query plan, we need it there so that
  	 * the executor still performs appropriate permissions checks for the
  	 * query caller's use of the view.
  	 */
  	new_rte->checkAsUser = view->rd_rel->relowner;
  	new_rte->requiredPerms = view_rte->requiredPerms;
  
  	/*
  	 * Now for the per-column permissions bits.
  	 *
  	 * Initially, new_rte contains selectedCols permission check bits for all
  	 * base-rel columns referenced by the view, but since the view is a SELECT
  	 * query its insertedCols/updatedCols is empty.  We set insertedCols and
  	 * updatedCols to include all the columns the outer query is trying to
  	 * modify, adjusting the column numbers as needed.  But we leave
  	 * selectedCols as-is, so the view owner must have read permission for all
  	 * columns used in the view definition, even if some of them are not read
  	 * by the outer query.  We could try to limit selectedCols to only columns
  	 * used in the transformed query, but that does not correspond to what
  	 * happens in ordinary SELECT usage of a view: all referenced columns must
  	 * have read permission, even if optimization finds that some of them can
  	 * be discarded during query transformation.  The flattening we're doing
  	 * here is an optional optimization, too.  (If you are unpersuaded and
  	 * want to change this, note that applying adjust_view_column_set to
  	 * view_rte->selectedCols is clearly *not* the right answer, since that
  	 * neglects base-rel columns used in the view's WHERE quals.)
  	 *
  	 * This step needs the modified view targetlist, so we have to do things
  	 * in this order.
  	 */
  	Assert(bms_is_empty(new_rte->insertedCols) &&
  		   bms_is_empty(new_rte->updatedCols));
  
  	new_rte->insertedCols = adjust_view_column_set(view_rte->insertedCols,
  												   view_targetlist);
  
  	new_rte->updatedCols = adjust_view_column_set(view_rte->updatedCols,
  												  view_targetlist);
  
  	/*
  	 * Move any security barrier quals from the view RTE onto the new target
  	 * RTE.  Any such quals should now apply to the new target RTE and will
  	 * not reference the original view RTE in the rewritten query.
  	 */
  	new_rte->securityQuals = view_rte->securityQuals;
  	view_rte->securityQuals = NIL;
  
  	/*
  	 * For UPDATE/DELETE, rewriteTargetListUD will have added a wholerow junk
  	 * TLE for the view to the end of the targetlist, which we no longer need.
  	 * Remove it to avoid unnecessary work when we process the targetlist.
  	 * Note that when we recurse through rewriteQuery a new junk TLE will be
  	 * added to allow the executor to find the proper row in the new target
  	 * relation.  (So, if we failed to do this, we might have multiple junk
  	 * TLEs with the same name, which would be disastrous.)
  	 */
  	if (parsetree->commandType != CMD_INSERT)
  	{
  		TargetEntry *tle = (TargetEntry *) llast(parsetree->targetList);
  
  		Assert(tle->resjunk);
  		Assert(IsA(tle->expr, Var) &&
  			   ((Var *) tle->expr)->varno == parsetree->resultRelation &&
  			   ((Var *) tle->expr)->varattno == 0);
  		parsetree->targetList = list_delete_ptr(parsetree->targetList, tle);
  	}
  
  	/*
  	 * Now update all Vars in the outer query that reference the view to
  	 * reference the appropriate column of the base relation instead.
  	 */
  	parsetree = (Query *)
  		ReplaceVarsFromTargetList((Node *) parsetree,
  								  parsetree->resultRelation,
  								  0,
  								  view_rte,
  								  view_targetlist,
  								  REPLACEVARS_REPORT_ERROR,
  								  0,
  								  &parsetree->hasSubLinks);
  
  	/*
  	 * Update all other RTI references in the query that point to the view
  	 * (for example, parsetree->resultRelation itself) to point to the new
  	 * base relation instead.  Vars will not be affected since none of them
  	 * reference parsetree->resultRelation any longer.
  	 */
  	ChangeVarNodes((Node *) parsetree,
  				   parsetree->resultRelation,
  				   new_rt_index,
  				   0);
  	Assert(parsetree->resultRelation == new_rt_index);
  
  	/*
  	 * For INSERT/UPDATE we must also update resnos in the targetlist to refer
  	 * to columns of the base relation, since those indicate the target
  	 * columns to be affected.
  	 *
  	 * Note that this destroys the resno ordering of the targetlist, but that
  	 * will be fixed when we recurse through rewriteQuery, which will invoke
  	 * rewriteTargetListIU again on the updated targetlist.
  	 */
  	if (parsetree->commandType != CMD_DELETE)
  	{
  		foreach(lc, parsetree->targetList)
  		{
  			TargetEntry *tle = (TargetEntry *) lfirst(lc);
  			TargetEntry *view_tle;
  
  			if (tle->resjunk)
  				continue;
  
  			view_tle = get_tle_by_resno(view_targetlist, tle->resno);
  			if (view_tle != NULL && !view_tle->resjunk && IsA(view_tle->expr, Var))
  				tle->resno = ((Var *) view_tle->expr)->varattno;
  			else
  				elog(ERROR, "attribute number %d not found in view targetlist",
  					 tle->resno);
  		}
  	}
  
  	/*
  	 * For UPDATE/DELETE, pull up any WHERE quals from the view.  We know that
  	 * any Vars in the quals must reference the one base relation, so we need
  	 * only adjust their varnos to reference the new target (just the same as
  	 * we did with the view targetlist).
  	 *
  	 * If it's a security-barrier view, its WHERE quals must be applied before
  	 * quals from the outer query, so we attach them to the RTE as security
  	 * barrier quals rather than adding them to the main WHERE clause.
  	 *
  	 * For INSERT, the view's quals can be ignored in the main query.
  	 */
  	if (parsetree->commandType != CMD_INSERT &&
  		viewquery->jointree->quals != NULL)
  	{
  		Node	   *viewqual = (Node *) viewquery->jointree->quals;
  
  		/*
  		 * Even though we copied viewquery already at the top of this
  		 * function, we must duplicate the viewqual again here, because we may
  		 * need to use the quals again below for a WithCheckOption clause.
  		 */
  		viewqual = copyObject(viewqual);
  
  		ChangeVarNodes(viewqual, base_rt_index, new_rt_index, 0);
  
  		if (RelationIsSecurityView(view))
  		{
  			/*
  			 * The view's quals go in front of existing barrier quals: those
  			 * would have come from an outer level of security-barrier view,
  			 * and so must get evaluated later.
  			 *
  			 * Note: the parsetree has been mutated, so the new_rte pointer is
  			 * stale and needs to be re-computed.
  			 */
  			new_rte = rt_fetch(new_rt_index, parsetree->rtable);
  			new_rte->securityQuals = lcons(viewqual, new_rte->securityQuals);
  
  			/*
  			 * Do not set parsetree->hasRowSecurity, because these aren't RLS
  			 * conditions (they aren't affected by enabling/disabling RLS).
  			 */
  
  			/*
  			 * Make sure that the query is marked correctly if the added qual
  			 * has sublinks.
  			 */
  			if (!parsetree->hasSubLinks)
  				parsetree->hasSubLinks = checkExprHasSubLink(viewqual);
  		}
  		else
  			AddQual(parsetree, (Node *) viewqual);
  	}
  
  	/*
  	 * For INSERT/UPDATE, if the view has the WITH CHECK OPTION, or any parent
  	 * view specified WITH CASCADED CHECK OPTION, add the quals from the view
  	 * to the query's withCheckOptions list.
  	 */
  	if (parsetree->commandType != CMD_DELETE)
  	{
  		bool		has_wco = RelationHasCheckOption(view);
  		bool		cascaded = RelationHasCascadedCheckOption(view);
  
  		/*
  		 * If the parent view has a cascaded check option, treat this view as
  		 * if it also had a cascaded check option.
  		 *
  		 * New WithCheckOptions are added to the start of the list, so if
  		 * there is a cascaded check option, it will be the first item in the
  		 * list.
  		 */
  		if (parsetree->withCheckOptions != NIL)
  		{
  			WithCheckOption *parent_wco =
  			(WithCheckOption *) linitial(parsetree->withCheckOptions);
  
  			if (parent_wco->cascaded)
  			{
  				has_wco = true;
  				cascaded = true;
  			}
  		}
  
  		/*
  		 * Add the new WithCheckOption to the start of the list, so that
  		 * checks on inner views are run before checks on outer views, as
  		 * required by the SQL standard.
  		 *
  		 * If the new check is CASCADED, we need to add it even if this view
  		 * has no quals, since there may be quals on child views.  A LOCAL
  		 * check can be omitted if this view has no quals.
  		 */
  		if (has_wco && (cascaded || viewquery->jointree->quals != NULL))
  		{
  			WithCheckOption *wco;
  
  			wco = makeNode(WithCheckOption);
  			wco->kind = WCO_VIEW_CHECK;
  			wco->relname = pstrdup(RelationGetRelationName(view));
  			wco->polname = NULL;
  			wco->qual = NULL;
  			wco->cascaded = cascaded;
  
  			parsetree->withCheckOptions = lcons(wco,
  												parsetree->withCheckOptions);
  
  			if (viewquery->jointree->quals != NULL)
  			{
  				wco->qual = (Node *) viewquery->jointree->quals;
  				ChangeVarNodes(wco->qual, base_rt_index, new_rt_index, 0);
  
  				/*
  				 * Make sure that the query is marked correctly if the added
  				 * qual has sublinks.  We can skip this check if the query is
  				 * already marked, or if the command is an UPDATE, in which
  				 * case the same qual will have already been added, and this
  				 * check will already have been done.
  				 */
  				if (!parsetree->hasSubLinks &&
  					parsetree->commandType != CMD_UPDATE)
  					parsetree->hasSubLinks = checkExprHasSubLink(wco->qual);
  			}
  		}
  	}
  
  	return parsetree;
  }
  
  
  /*
   * RewriteQuery -
   *	  rewrites the query and apply the rules again on the queries rewritten
   *
   * rewrite_events is a list of open query-rewrite actions, so we can detect
   * infinite recursion.
   */
  static List *
  RewriteQuery(Query *parsetree, List *rewrite_events)
  {
  	CmdType		event = parsetree->commandType;
  	bool		instead = false;
  	bool		returning = false;
  	bool		updatableview = false;
  	Query	   *qual_product = NULL;
  	List	   *rewritten = NIL;
  	ListCell   *lc1;
  
  	/*
  	 * First, recursively process any insert/update/delete statements in WITH
  	 * clauses.  (We have to do this first because the WITH clauses may get
  	 * copied into rule actions below.)
  	 */
  	foreach(lc1, parsetree->cteList)
  	{
  		CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc1);
  		Query	   *ctequery = (Query *) cte->ctequery;
  		List	   *newstuff;
  
  		Assert(IsA(ctequery, Query));
  
  		if (ctequery->commandType == CMD_SELECT)
  			continue;
  
  		newstuff = RewriteQuery(ctequery, rewrite_events);
  
  		/*
  		 * Currently we can only handle unconditional, single-statement DO
  		 * INSTEAD rules correctly; we have to get exactly one Query out of
  		 * the rewrite operation to stuff back into the CTE node.
  		 */
  		if (list_length(newstuff) == 1)
  		{
  			/* Push the single Query back into the CTE node */
  			ctequery = (Query *) linitial(newstuff);
  			Assert(IsA(ctequery, Query));
  			/* WITH queries should never be canSetTag */
  			Assert(!ctequery->canSetTag);
  			cte->ctequery = (Node *) ctequery;
  		}
  		else if (newstuff == NIL)
  		{
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("DO INSTEAD NOTHING rules are not supported for data-modifying statements in WITH")));
  		}
  		else
  		{
  			ListCell   *lc2;
  
  			/* examine queries to determine which error message to issue */
  			foreach(lc2, newstuff)
  			{
  				Query	   *q = (Query *) lfirst(lc2);
  
  				if (q->querySource == QSRC_QUAL_INSTEAD_RULE)
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  							 errmsg("conditional DO INSTEAD rules are not supported for data-modifying statements in WITH")));
  				if (q->querySource == QSRC_NON_INSTEAD_RULE)
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  							 errmsg("DO ALSO rules are not supported for data-modifying statements in WITH")));
  			}
  
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("multi-statement DO INSTEAD rules are not supported for data-modifying statements in WITH")));
  		}
  	}
  
  	/*
  	 * If the statement is an insert, update, or delete, adjust its targetlist
  	 * as needed, and then fire INSERT/UPDATE/DELETE rules on it.
  	 *
  	 * SELECT rules are handled later when we have all the queries that should
  	 * get executed.  Also, utilities aren't rewritten at all (do we still
  	 * need that check?)
  	 */
  	if (event != CMD_SELECT && event != CMD_UTILITY)
  	{
  		int			result_relation;
  		RangeTblEntry *rt_entry;
  		Relation	rt_entry_relation;
  		List	   *locks;
  		List	   *product_queries;
  		bool		hasUpdate = false;
  
  		result_relation = parsetree->resultRelation;
  		Assert(result_relation != 0);
  		rt_entry = rt_fetch(result_relation, parsetree->rtable);
  		Assert(rt_entry->rtekind == RTE_RELATION);
  
  		/*
  		 * We can use NoLock here since either the parser or
  		 * AcquireRewriteLocks should have locked the rel already.
  		 */
  		rt_entry_relation = heap_open(rt_entry->relid, NoLock);
  
  		/*
  		 * Rewrite the targetlist as needed for the command type.
  		 */
  		if (event == CMD_INSERT)
  		{
  			RangeTblEntry *values_rte = NULL;
  
  			/*
  			 * If it's an INSERT ... VALUES (...), (...), ... there will be a
  			 * single RTE for the VALUES targetlists.
  			 */
  			if (list_length(parsetree->jointree->fromlist) == 1)
  			{
  				RangeTblRef *rtr = (RangeTblRef *) linitial(parsetree->jointree->fromlist);
  
  				if (IsA(rtr, RangeTblRef))
  				{
  					RangeTblEntry *rte = rt_fetch(rtr->rtindex,
  												  parsetree->rtable);
  
  					if (rte->rtekind == RTE_VALUES)
  						values_rte = rte;
  				}
  			}
  
  			if (values_rte)
  			{
  				List	   *attrnos;
  
  				/* Process the main targetlist ... */
  				parsetree->targetList = rewriteTargetListIU(parsetree->targetList,
  													  parsetree->commandType,
  															rt_entry_relation,
  												   parsetree->resultRelation,
  															&attrnos);
  				/* ... and the VALUES expression lists */
  				rewriteValuesRTE(values_rte, rt_entry_relation, attrnos);
  			}
  			else
  			{
  				/* Process just the main targetlist */
  				parsetree->targetList =
  					rewriteTargetListIU(parsetree->targetList,
  										parsetree->commandType,
  										rt_entry_relation,
  										parsetree->resultRelation, NULL);
  			}
  
  			if (parsetree->onConflict &&
  				parsetree->onConflict->action == ONCONFLICT_UPDATE)
  			{
  				parsetree->onConflict->onConflictSet =
  					rewriteTargetListIU(parsetree->onConflict->onConflictSet,
  										CMD_UPDATE,
  										rt_entry_relation,
  										parsetree->resultRelation,
  										NULL);
  			}
  		}
  		else if (event == CMD_UPDATE)
  		{
  			parsetree->targetList =
  				rewriteTargetListIU(parsetree->targetList,
  									parsetree->commandType, rt_entry_relation,
  									parsetree->resultRelation, NULL);
  			rewriteTargetListUD(parsetree, rt_entry, rt_entry_relation);
  		}
  		else if (event == CMD_DELETE)
  		{
  			rewriteTargetListUD(parsetree, rt_entry, rt_entry_relation);
  		}
  		else
  			elog(ERROR, "unrecognized commandType: %d", (int) event);
  
  		/*
  		 * Collect and apply the appropriate rules.
  		 */
  		locks = matchLocks(event, rt_entry_relation->rd_rules,
  						   result_relation, parsetree, &hasUpdate);
  
  		product_queries = fireRules(parsetree,
  									result_relation,
  									event,
  									locks,
  									&instead,
  									&returning,
  									&qual_product);
  
  		/*
  		 * If there were no INSTEAD rules, and the target relation is a view
  		 * without any INSTEAD OF triggers, see if the view can be
  		 * automatically updated.  If so, we perform the necessary query
  		 * transformation here and add the resulting query to the
  		 * product_queries list, so that it gets recursively rewritten if
  		 * necessary.
  		 */
  		if (!instead && qual_product == NULL &&
  			rt_entry_relation->rd_rel->relkind == RELKIND_VIEW &&
  			!view_has_instead_trigger(rt_entry_relation, event))
  		{
  			/*
  			 * This throws an error if the view can't be automatically
  			 * updated, but that's OK since the query would fail at runtime
  			 * anyway.
  			 */
  			parsetree = rewriteTargetView(parsetree, rt_entry_relation);
  
  			/*
  			 * At this point product_queries contains any DO ALSO rule
  			 * actions. Add the rewritten query before or after those.  This
  			 * must match the handling the original query would have gotten
  			 * below, if we allowed it to be included again.
  			 */
  			if (parsetree->commandType == CMD_INSERT)
  				product_queries = lcons(parsetree, product_queries);
  			else
  				product_queries = lappend(product_queries, parsetree);
  
  			/*
  			 * Set the "instead" flag, as if there had been an unqualified
  			 * INSTEAD, to prevent the original query from being included a
  			 * second time below.  The transformation will have rewritten any
  			 * RETURNING list, so we can also set "returning" to forestall
  			 * throwing an error below.
  			 */
  			instead = true;
  			returning = true;
  			updatableview = true;
  		}
  
  		/*
  		 * If we got any product queries, recursively rewrite them --- but
  		 * first check for recursion!
  		 */
  		if (product_queries != NIL)
  		{
  			ListCell   *n;
  			rewrite_event *rev;
  
  			foreach(n, rewrite_events)
  			{
  				rev = (rewrite_event *) lfirst(n);
  				if (rev->relation == RelationGetRelid(rt_entry_relation) &&
  					rev->event == event)
  					ereport(ERROR,
  							(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  							 errmsg("infinite recursion detected in rules for relation \"%s\"",
  							   RelationGetRelationName(rt_entry_relation))));
  			}
  
  			rev = (rewrite_event *) palloc(sizeof(rewrite_event));
  			rev->relation = RelationGetRelid(rt_entry_relation);
  			rev->event = event;
  			rewrite_events = lcons(rev, rewrite_events);
  
  			foreach(n, product_queries)
  			{
  				Query	   *pt = (Query *) lfirst(n);
  				List	   *newstuff;
  
  				newstuff = RewriteQuery(pt, rewrite_events);
  				rewritten = list_concat(rewritten, newstuff);
  			}
  
  			rewrite_events = list_delete_first(rewrite_events);
  		}
  
  		/*
  		 * If there is an INSTEAD, and the original query has a RETURNING, we
  		 * have to have found a RETURNING in the rule(s), else fail. (Because
  		 * DefineQueryRewrite only allows RETURNING in unconditional INSTEAD
  		 * rules, there's no need to worry whether the substituted RETURNING
  		 * will actually be executed --- it must be.)
  		 */
  		if ((instead || qual_product != NULL) &&
  			parsetree->returningList &&
  			!returning)
  		{
  			switch (event)
  			{
  				case CMD_INSERT:
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  							 errmsg("cannot perform INSERT RETURNING on relation \"%s\"",
  								 RelationGetRelationName(rt_entry_relation)),
  							 errhint("You need an unconditional ON INSERT DO INSTEAD rule with a RETURNING clause.")));
  					break;
  				case CMD_UPDATE:
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  							 errmsg("cannot perform UPDATE RETURNING on relation \"%s\"",
  								 RelationGetRelationName(rt_entry_relation)),
  							 errhint("You need an unconditional ON UPDATE DO INSTEAD rule with a RETURNING clause.")));
  					break;
  				case CMD_DELETE:
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  							 errmsg("cannot perform DELETE RETURNING on relation \"%s\"",
  								 RelationGetRelationName(rt_entry_relation)),
  							 errhint("You need an unconditional ON DELETE DO INSTEAD rule with a RETURNING clause.")));
  					break;
  				default:
  					elog(ERROR, "unrecognized commandType: %d",
  						 (int) event);
  					break;
  			}
  		}
  
  		/*
  		 * Updatable views are supported by ON CONFLICT, so don't prevent that
  		 * case from proceeding
  		 */
  		if (parsetree->onConflict &&
  			(product_queries != NIL || hasUpdate) &&
  			!updatableview)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("INSERT with ON CONFLICT clause cannot be used with table that has INSERT or UPDATE rules")));
  
  		heap_close(rt_entry_relation, NoLock);
  	}
  
  	/*
  	 * For INSERTs, the original query is done first; for UPDATE/DELETE, it is
  	 * done last.  This is needed 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 executions
  	 * makes the deleted (and maybe the updated) tuples disappear so the scans
  	 * for them in the rule actions cannot find them.
  	 *
  	 * If we found any unqualified INSTEAD, the original query is not done at
  	 * all, in any form.  Otherwise, we add the modified form if qualified
  	 * INSTEADs were found, else the unmodified form.
  	 */
  	if (!instead)
  	{
  		if (parsetree->commandType == CMD_INSERT)
  		{
  			if (qual_product != NULL)
  				rewritten = lcons(qual_product, rewritten);
  			else
  				rewritten = lcons(parsetree, rewritten);
  		}
  		else
  		{
  			if (qual_product != NULL)
  				rewritten = lappend(rewritten, qual_product);
  			else
  				rewritten = lappend(rewritten, parsetree);
  		}
  	}
  
  	/*
  	 * If the original query has a CTE list, and we generated more than one
  	 * non-utility result query, we have to fail because we'll have copied the
  	 * CTE list into each result query.  That would break the expectation of
  	 * single evaluation of CTEs.  This could possibly be fixed by
  	 * restructuring so that a CTE list can be shared across multiple Query
  	 * and PlannableStatement nodes.
  	 */
  	if (parsetree->cteList != NIL)
  	{
  		int			qcount = 0;
  
  		foreach(lc1, rewritten)
  		{
  			Query	   *q = (Query *) lfirst(lc1);
  
  			if (q->commandType != CMD_UTILITY)
  				qcount++;
  		}
  		if (qcount > 1)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("WITH cannot be used in a query that is rewritten by rules into multiple queries")));
  	}
  
  	return rewritten;
  }
  
  
  /*
   * QueryRewrite -
   *	  Primary entry point to the query rewriter.
   *	  Rewrite one query via query rewrite system, possibly returning 0
   *	  or many queries.
   *
   * NOTE: the parsetree must either have come straight from the parser,
   * or have been scanned by AcquireRewriteLocks to acquire suitable locks.
   */
  List *
  QueryRewrite(Query *parsetree)
  {
  	uint32		input_query_id = parsetree->queryId;
  	List	   *querylist;
  	List	   *results;
  	ListCell   *l;
  	CmdType		origCmdType;
  	bool		foundOriginalQuery;
  	Query	   *lastInstead;
  
  	/*
  	 * This function is only applied to top-level original queries
  	 */
  	Assert(parsetree->querySource == QSRC_ORIGINAL);
  	Assert(parsetree->canSetTag);
  
  	/*
  	 * Step 1
  	 *
  	 * Apply all non-SELECT rules possibly getting 0 or many queries
  	 */
  	querylist = RewriteQuery(parsetree, NIL);
  
  	/*
  	 * Step 2
  	 *
  	 * Apply all the RIR rules on each query
  	 *
  	 * This is also a handy place to mark each query with the original queryId
  	 */
  	results = NIL;
  	foreach(l, querylist)
  	{
  		Query	   *query = (Query *) lfirst(l);
  
  		query = fireRIRrules(query, NIL, false);
  
  		query->queryId = input_query_id;
  
  		results = lappend(results, query);
  	}
  
  	/*
  	 * Step 3
  	 *
  	 * Determine which, if any, of the resulting queries is supposed to set
  	 * the command-result tag; and update the canSetTag fields accordingly.
  	 *
  	 * If the original query is still in the list, it sets the command tag.
  	 * Otherwise, the last INSTEAD query of the same kind as the original is
  	 * allowed to set the tag.  (Note these rules can leave us with no query
  	 * setting the tag.  The tcop code has to cope with this by setting up a
  	 * default tag based on the original un-rewritten query.)
  	 *
  	 * The Asserts verify that at most one query in the result list is marked
  	 * canSetTag.  If we aren't checking asserts, we can fall out of the loop
  	 * as soon as we find the original query.
  	 */
  	origCmdType = parsetree->commandType;
  	foundOriginalQuery = false;
  	lastInstead = NULL;
  
  	foreach(l, results)
  	{
  		Query	   *query = (Query *) lfirst(l);
  
  		if (query->querySource == QSRC_ORIGINAL)
  		{
  			Assert(query->canSetTag);
  			Assert(!foundOriginalQuery);
  			foundOriginalQuery = true;
  #ifndef USE_ASSERT_CHECKING
  			break;
  #endif
  		}
  		else
  		{
  			Assert(!query->canSetTag);
  			if (query->commandType == origCmdType &&
  				(query->querySource == QSRC_INSTEAD_RULE ||
  				 query->querySource == QSRC_QUAL_INSTEAD_RULE))
  				lastInstead = query;
  		}
  	}
  
  	if (!foundOriginalQuery && lastInstead != NULL)
  		lastInstead->canSetTag = true;
  
  	return results;
  }
  