text: /*-------------------------------------------------------------------------
   *
   * rewriteDefine.c
   *	  routines for defining a rewrite rule
   *
   * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  src/backend/rewrite/rewriteDefine.c
   *
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include "access/heapam.h"
  #include "access/htup_details.h"
  #include "access/multixact.h"
  #include "access/transam.h"
  #include "access/xact.h"
  #include "catalog/catalog.h"
  #include "catalog/dependency.h"
  #include "catalog/heap.h"
  #include "catalog/indexing.h"
  #include "catalog/namespace.h"
  #include "catalog/objectaccess.h"
  #include "catalog/pg_rewrite.h"
  #include "catalog/storage.h"
  #include "commands/policy.h"
  #include "miscadmin.h"
  #include "nodes/nodeFuncs.h"
  #include "parser/parse_utilcmd.h"
  #include "rewrite/rewriteDefine.h"
  #include "rewrite/rewriteManip.h"
  #include "rewrite/rewriteSupport.h"
  #include "utils/acl.h"
  #include "utils/builtins.h"
  #include "utils/inval.h"
  #include "utils/lsyscache.h"
  #include "utils/rel.h"
  #include "utils/snapmgr.h"
  #include "utils/syscache.h"
  #include "utils/tqual.h"
  
  
  static void checkRuleResultList(List *targetList, TupleDesc resultDesc,
  					bool isSelect, bool requireColumnNameMatch);
  static bool setRuleCheckAsUser_walker(Node *node, Oid *context);
  static void setRuleCheckAsUser_Query(Query *qry, Oid userid);
  
  
  /*
   * InsertRule -
   *	  takes the arguments and inserts them as a row into the system
   *	  relation "pg_rewrite"
   */
  static Oid
  InsertRule(char *rulname,
  		   int evtype,
  		   Oid eventrel_oid,
  		   bool evinstead,
  		   Node *event_qual,
  		   List *action,
  		   bool replace)
  {
  	char	   *evqual = nodeToString(event_qual);
  	char	   *actiontree = nodeToString((Node *) action);
  	Datum		values[Natts_pg_rewrite];
  	bool		nulls[Natts_pg_rewrite];
  	bool		replaces[Natts_pg_rewrite];
  	NameData	rname;
  	Relation	pg_rewrite_desc;
  	HeapTuple	tup,
  				oldtup;
  	Oid			rewriteObjectId;
  	ObjectAddress myself,
  				referenced;
  	bool		is_update = false;
  
  	/*
  	 * Set up *nulls and *values arrays
  	 */
  	MemSet(nulls, false, sizeof(nulls));
  
  	namestrcpy(&rname, rulname);
  	values[Anum_pg_rewrite_rulename - 1] = NameGetDatum(&rname);
  	values[Anum_pg_rewrite_ev_class - 1] = ObjectIdGetDatum(eventrel_oid);
  	values[Anum_pg_rewrite_ev_type - 1] = CharGetDatum(evtype + '0');
  	values[Anum_pg_rewrite_ev_enabled - 1] = CharGetDatum(RULE_FIRES_ON_ORIGIN);
  	values[Anum_pg_rewrite_is_instead - 1] = BoolGetDatum(evinstead);
  	values[Anum_pg_rewrite_ev_qual - 1] = CStringGetTextDatum(evqual);
  	values[Anum_pg_rewrite_ev_action - 1] = CStringGetTextDatum(actiontree);
  
  	/*
  	 * Ready to store new pg_rewrite tuple
  	 */
  	pg_rewrite_desc = heap_open(RewriteRelationId, RowExclusiveLock);
  
  	/*
  	 * Check to see if we are replacing an existing tuple
  	 */
  	oldtup = SearchSysCache2(RULERELNAME,
  							 ObjectIdGetDatum(eventrel_oid),
  							 PointerGetDatum(rulname));
  
  	if (HeapTupleIsValid(oldtup))
  	{
  		if (!replace)
  			ereport(ERROR,
  					(errcode(ERRCODE_DUPLICATE_OBJECT),
  					 errmsg("rule \"%s\" for relation \"%s\" already exists",
  							rulname, get_rel_name(eventrel_oid))));
  
  		/*
  		 * When replacing, we don't need to replace every attribute
  		 */
  		MemSet(replaces, false, sizeof(replaces));
  		replaces[Anum_pg_rewrite_ev_type - 1] = true;
  		replaces[Anum_pg_rewrite_is_instead - 1] = true;
  		replaces[Anum_pg_rewrite_ev_qual - 1] = true;
  		replaces[Anum_pg_rewrite_ev_action - 1] = true;
  
  		tup = heap_modify_tuple(oldtup, RelationGetDescr(pg_rewrite_desc),
  								values, nulls, replaces);
  
  		simple_heap_update(pg_rewrite_desc, &tup->t_self, tup);
  
  		ReleaseSysCache(oldtup);
  
  		rewriteObjectId = HeapTupleGetOid(tup);
  		is_update = true;
  	}
  	else
  	{
  		tup = heap_form_tuple(pg_rewrite_desc->rd_att, values, nulls);
  
  		rewriteObjectId = simple_heap_insert(pg_rewrite_desc, tup);
  	}
  
  	/* Need to update indexes in either case */
  	CatalogUpdateIndexes(pg_rewrite_desc, tup);
  
  	heap_freetuple(tup);
  
  	/* If replacing, get rid of old dependencies and make new ones */
  	if (is_update)
  		deleteDependencyRecordsFor(RewriteRelationId, rewriteObjectId, false);
  
  	/*
  	 * Install dependency on rule's relation to ensure it will go away on
  	 * relation deletion.  If the rule is ON SELECT, make the dependency
  	 * implicit --- this prevents deleting a view's SELECT rule.  Other kinds
  	 * of rules can be AUTO.
  	 */
  	myself.classId = RewriteRelationId;
  	myself.objectId = rewriteObjectId;
  	myself.objectSubId = 0;
  
  	referenced.classId = RelationRelationId;
  	referenced.objectId = eventrel_oid;
  	referenced.objectSubId = 0;
  
  	recordDependencyOn(&myself, &referenced,
  			 (evtype == CMD_SELECT) ? DEPENDENCY_INTERNAL : DEPENDENCY_AUTO);
  
  	/*
  	 * Also install dependencies on objects referenced in action and qual.
  	 */
  	recordDependencyOnExpr(&myself, (Node *) action, NIL,
  						   DEPENDENCY_NORMAL);
  
  	if (event_qual != NULL)
  	{
  		/* Find query containing OLD/NEW rtable entries */
  		Query	   *qry = (Query *) linitial(action);
  
  		qry = getInsertSelectQuery(qry, NULL);
  		recordDependencyOnExpr(&myself, event_qual, qry->rtable,
  							   DEPENDENCY_NORMAL);
  	}
  
  	/* Post creation hook for new rule */
  	InvokeObjectPostCreateHook(RewriteRelationId, rewriteObjectId, 0);
  
  	heap_close(pg_rewrite_desc, RowExclusiveLock);
  
  	return rewriteObjectId;
  }
  
  /*
   * DefineRule
   *		Execute a CREATE RULE command.
   */
  ObjectAddress
  DefineRule(RuleStmt *stmt, const char *queryString)
  {
  	List	   *actions;
  	Node	   *whereClause;
  	Oid			relId;
  
  	/* Parse analysis. */
  	transformRuleStmt(stmt, queryString, &actions, &whereClause);
  
  	/*
  	 * Find and lock the relation.  Lock level should match
  	 * DefineQueryRewrite.
  	 */
  	relId = RangeVarGetRelid(stmt->relation, AccessExclusiveLock, false);
  
  	/* ... and execute */
  	return DefineQueryRewrite(stmt->rulename,
  							  relId,
  							  whereClause,
  							  stmt->event,
  							  stmt->instead,
  							  stmt->replace,
  							  actions);
  }
  
  
  /*
   * DefineQueryRewrite
   *		Create a rule
   *
   * This is essentially the same as DefineRule() except that the rule's
   * action and qual have already been passed through parse analysis.
   */
  ObjectAddress
  DefineQueryRewrite(char *rulename,
  				   Oid event_relid,
  				   Node *event_qual,
  				   CmdType event_type,
  				   bool is_instead,
  				   bool replace,
  				   List *action)
  {
  	Relation	event_relation;
  	ListCell   *l;
  	Query	   *query;
  	bool		RelisBecomingView = false;
  	Oid			ruleId = InvalidOid;
  	ObjectAddress address;
  
  	/*
  	 * If we are installing an ON SELECT rule, we had better grab
  	 * AccessExclusiveLock to ensure no SELECTs are currently running on the
  	 * event relation. For other types of rules, it would be sufficient to
  	 * grab ShareRowExclusiveLock to lock out insert/update/delete actions and
  	 * to ensure that we lock out current CREATE RULE statements; but because
  	 * of race conditions in access to catalog entries, we can't do that yet.
  	 *
  	 * Note that this lock level should match the one used in DefineRule.
  	 */
  	event_relation = heap_open(event_relid, AccessExclusiveLock);
  
  	/*
  	 * Verify relation is of a type that rules can sensibly be applied to.
  	 * Internal callers can target materialized views, but transformRuleStmt()
  	 * blocks them for users.  Don't mention them in the error message.
  	 */
  	if (event_relation->rd_rel->relkind != RELKIND_RELATION &&
  		event_relation->rd_rel->relkind != RELKIND_MATVIEW &&
  		event_relation->rd_rel->relkind != RELKIND_VIEW)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a table or view",
  						RelationGetRelationName(event_relation))));
  
  	if (!allowSystemTableMods && IsSystemRelation(event_relation))
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("permission denied: \"%s\" is a system catalog",
  						RelationGetRelationName(event_relation))));
  
  	/*
  	 * Check user has permission to apply rules to this relation.
  	 */
  	if (!pg_class_ownercheck(event_relid, GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
  					   RelationGetRelationName(event_relation));
  
  	/*
  	 * No rule actions that modify OLD or NEW
  	 */
  	foreach(l, action)
  	{
  		query = (Query *) lfirst(l);
  		if (query->resultRelation == 0)
  			continue;
  		/* Don't be fooled by INSERT/SELECT */
  		if (query != getInsertSelectQuery(query, NULL))
  			continue;
  		if (query->resultRelation == PRS2_OLD_VARNO)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("rule actions on OLD are not implemented"),
  					 errhint("Use views or triggers instead.")));
  		if (query->resultRelation == PRS2_NEW_VARNO)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("rule actions on NEW are not implemented"),
  					 errhint("Use triggers instead.")));
  	}
  
  	if (event_type == CMD_SELECT)
  	{
  		/*
  		 * Rules ON SELECT are restricted to view definitions
  		 *
  		 * So there cannot be INSTEAD NOTHING, ...
  		 */
  		if (list_length(action) == 0)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  			   errmsg("INSTEAD NOTHING rules on SELECT are not implemented"),
  					 errhint("Use views instead.")));
  
  		/*
  		 * ... there cannot be multiple actions, ...
  		 */
  		if (list_length(action) > 1)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("multiple actions for rules on SELECT are not implemented")));
  
  		/*
  		 * ... the one action must be a SELECT, ...
  		 */
  		query = (Query *) linitial(action);
  		if (!is_instead ||
  			query->commandType != CMD_SELECT ||
  			query->utilityStmt != NULL)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("rules on SELECT must have action INSTEAD SELECT")));
  
  		/*
  		 * ... it cannot contain data-modifying WITH ...
  		 */
  		if (query->hasModifyingCTE)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("rules on SELECT must not contain data-modifying statements in WITH")));
  
  		/*
  		 * ... there can be no rule qual, ...
  		 */
  		if (event_qual != NULL)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("event qualifications are not implemented for rules on SELECT")));
  
  		/*
  		 * ... the targetlist of the SELECT action must exactly match the
  		 * event relation, ...
  		 */
  		checkRuleResultList(query->targetList,
  							RelationGetDescr(event_relation),
  							true,
  							event_relation->rd_rel->relkind !=
  							RELKIND_MATVIEW);
  
  		/*
  		 * ... there must not be another ON SELECT rule already ...
  		 */
  		if (!replace && event_relation->rd_rules != NULL)
  		{
  			int			i;
  
  			for (i = 0; i < event_relation->rd_rules->numLocks; i++)
  			{
  				RewriteRule *rule;
  
  				rule = event_relation->rd_rules->rules[i];
  				if (rule->event == CMD_SELECT)
  					ereport(ERROR,
  						  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  						   errmsg("\"%s\" is already a view",
  								  RelationGetRelationName(event_relation))));
  			}
  		}
  
  		/*
  		 * ... and finally the rule must be named _RETURN.
  		 */
  		if (strcmp(rulename, ViewSelectRuleName) != 0)
  		{
  			/*
  			 * In versions before 7.3, the expected name was _RETviewname. For
  			 * backwards compatibility with old pg_dump output, accept that
  			 * and silently change it to _RETURN.  Since this is just a quick
  			 * backwards-compatibility hack, limit the number of characters
  			 * checked to a few less than NAMEDATALEN; this saves having to
  			 * worry about where a multibyte character might have gotten
  			 * truncated.
  			 */
  			if (strncmp(rulename, "_RET", 4) != 0 ||
  				strncmp(rulename + 4, RelationGetRelationName(event_relation),
  						NAMEDATALEN - 4 - 4) != 0)
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  						 errmsg("view rule for \"%s\" must be named \"%s\"",
  								RelationGetRelationName(event_relation),
  								ViewSelectRuleName)));
  			rulename = pstrdup(ViewSelectRuleName);
  		}
  
  		/*
  		 * Are we converting a relation to a view?
  		 *
  		 * If so, check that the relation is empty because the storage for the
  		 * relation is going to be deleted.  Also insist that the rel not have
  		 * any triggers, indexes, child tables, policies, or RLS enabled.
  		 * (Note: these tests are too strict, because they will reject
  		 * relations that once had such but don't anymore.  But we don't
  		 * really care, because this whole business of converting relations
  		 * to views is just a kluge to allow dump/reload of views that
  		 * participate in circular dependencies.)
  		 */
  		if (event_relation->rd_rel->relkind != RELKIND_VIEW &&
  			event_relation->rd_rel->relkind != RELKIND_MATVIEW)
  		{
  			HeapScanDesc scanDesc;
  			Snapshot	snapshot;
  
  			snapshot = RegisterSnapshot(GetLatestSnapshot());
  			scanDesc = heap_beginscan(event_relation, snapshot, 0, NULL);
  			if (heap_getnext(scanDesc, ForwardScanDirection) != NULL)
  				ereport(ERROR,
  						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  						 errmsg("could not convert table \"%s\" to a view because it is not empty",
  								RelationGetRelationName(event_relation))));
  			heap_endscan(scanDesc);
  			UnregisterSnapshot(snapshot);
  
  			if (event_relation->rd_rel->relhastriggers)
  				ereport(ERROR,
  						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  						 errmsg("could not convert table \"%s\" to a view because it has triggers",
  								RelationGetRelationName(event_relation)),
  						 errhint("In particular, the table cannot be involved in any foreign key relationships.")));
  
  			if (event_relation->rd_rel->relhasindex)
  				ereport(ERROR,
  						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  						 errmsg("could not convert table \"%s\" to a view because it has indexes",
  								RelationGetRelationName(event_relation))));
  
  			if (event_relation->rd_rel->relhassubclass)
  				ereport(ERROR,
  						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  						 errmsg("could not convert table \"%s\" to a view because it has child tables",
  								RelationGetRelationName(event_relation))));
  
  			if (event_relation->rd_rel->relrowsecurity)
  				ereport(ERROR,
  						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  						 errmsg("could not convert table \"%s\" to a view because it has row security enabled",
  								RelationGetRelationName(event_relation))));
  
  			if (relation_has_policies(event_relation))
  				ereport(ERROR,
  						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  						 errmsg("could not convert table \"%s\" to a view because it has row security policies",
  								RelationGetRelationName(event_relation))));
  
  			RelisBecomingView = true;
  		}
  	}
  	else
  	{
  		/*
  		 * For non-SELECT rules, a RETURNING list can appear in at most one of
  		 * the actions ... and there can't be any RETURNING list at all in a
  		 * conditional or non-INSTEAD rule.  (Actually, there can be at most
  		 * one RETURNING list across all rules on the same event, but it seems
  		 * best to enforce that at rule expansion time.)  If there is a
  		 * RETURNING list, it must match the event relation.
  		 */
  		bool		haveReturning = false;
  
  		foreach(l, action)
  		{
  			query = (Query *) lfirst(l);
  
  			if (!query->returningList)
  				continue;
  			if (haveReturning)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				  errmsg("cannot have multiple RETURNING lists in a rule")));
  			haveReturning = true;
  			if (event_qual != NULL)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("RETURNING lists are not supported in conditional rules")));
  			if (!is_instead)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("RETURNING lists are not supported in non-INSTEAD rules")));
  			checkRuleResultList(query->returningList,
  								RelationGetDescr(event_relation),
  								false, false);
  		}
  	}
  
  	/*
  	 * This rule is allowed - prepare to install it.
  	 */
  
  	/* discard rule if it's null action and not INSTEAD; it's a no-op */
  	if (action != NIL || is_instead)
  	{
  		ruleId = InsertRule(rulename,
  							event_type,
  							event_relid,
  							is_instead,
  							event_qual,
  							action,
  							replace);
  
  		/*
  		 * Set pg_class 'relhasrules' field TRUE for event relation.
  		 *
  		 * Important side effect: an SI notice is broadcast to force all
  		 * backends (including me!) to update relcache entries with the new
  		 * rule.
  		 */
  		SetRelationRuleStatus(event_relid, true);
  	}
  
  	/* ---------------------------------------------------------------------
  	 * If the relation is becoming a view:
  	 * - delete the associated storage files
  	 * - get rid of any system attributes in pg_attribute; a view shouldn't
  	 *	 have any of those
  	 * - remove the toast table; there is no need for it anymore, and its
  	 *	 presence would make vacuum slightly more complicated
  	 * - set relkind to RELKIND_VIEW, and adjust other pg_class fields
  	 *	 to be appropriate for a view
  	 *
  	 * NB: we had better have AccessExclusiveLock to do this ...
  	 * ---------------------------------------------------------------------
  	 */
  	if (RelisBecomingView)
  	{
  		Relation	relationRelation;
  		Oid			toastrelid;
  		HeapTuple	classTup;
  		Form_pg_class classForm;
  
  		relationRelation = heap_open(RelationRelationId, RowExclusiveLock);
  		toastrelid = event_relation->rd_rel->reltoastrelid;
  
  		/* drop storage while table still looks like a table  */
  		RelationDropStorage(event_relation);
  		DeleteSystemAttributeTuples(event_relid);
  
  		/*
  		 * Drop the toast table if any.  (This won't take care of updating the
  		 * toast fields in the relation's own pg_class entry; we handle that
  		 * below.)
  		 */
  		if (OidIsValid(toastrelid))
  		{
  			ObjectAddress toastobject;
  
  			/*
  			 * Delete the dependency of the toast relation on the main
  			 * relation so we can drop the former without dropping the latter.
  			 */
  			deleteDependencyRecordsFor(RelationRelationId, toastrelid,
  									   false);
  
  			/* Make deletion of dependency record visible */
  			CommandCounterIncrement();
  
  			/* Now drop toast table, including its index */
  			toastobject.classId = RelationRelationId;
  			toastobject.objectId = toastrelid;
  			toastobject.objectSubId = 0;
  			performDeletion(&toastobject, DROP_RESTRICT,
  							PERFORM_DELETION_INTERNAL);
  		}
  
  		/*
  		 * SetRelationRuleStatus may have updated the pg_class row, so we must
  		 * advance the command counter before trying to update it again.
  		 */
  		CommandCounterIncrement();
  
  		/*
  		 * Fix pg_class entry to look like a normal view's, including setting
  		 * the correct relkind and removal of reltoastrelid of the toast table
  		 * we potentially removed above.
  		 */
  		classTup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(event_relid));
  		if (!HeapTupleIsValid(classTup))
  			elog(ERROR, "cache lookup failed for relation %u", event_relid);
  		classForm = (Form_pg_class) GETSTRUCT(classTup);
  
  		classForm->reltablespace = InvalidOid;
  		classForm->relpages = 0;
  		classForm->reltuples = 0;
  		classForm->relallvisible = 0;
  		classForm->reltoastrelid = InvalidOid;
  		classForm->relhasindex = false;
  		classForm->relkind = RELKIND_VIEW;
  		classForm->relhasoids = false;
  		classForm->relhaspkey = false;
  		classForm->relfrozenxid = InvalidTransactionId;
  		classForm->relminmxid = InvalidMultiXactId;
  		classForm->relreplident = REPLICA_IDENTITY_NOTHING;
  
  		simple_heap_update(relationRelation, &classTup->t_self, classTup);
  		CatalogUpdateIndexes(relationRelation, classTup);
  
  		heap_freetuple(classTup);
  		heap_close(relationRelation, RowExclusiveLock);
  	}
  
  	ObjectAddressSet(address, RewriteRelationId, ruleId);
  
  	/* Close rel, but keep lock till commit... */
  	heap_close(event_relation, NoLock);
  
  	return address;
  }
  
  /*
   * checkRuleResultList
   *		Verify that targetList produces output compatible with a tupledesc
   *
   * The targetList might be either a SELECT targetlist, or a RETURNING list;
   * isSelect tells which.  This is used for choosing error messages.
   *
   * A SELECT targetlist may optionally require that column names match.
   */
  static void
  checkRuleResultList(List *targetList, TupleDesc resultDesc, bool isSelect,
  					bool requireColumnNameMatch)
  {
  	ListCell   *tllist;
  	int			i;
  
  	/* Only a SELECT may require a column name match. */
  	Assert(isSelect || !requireColumnNameMatch);
  
  	i = 0;
  	foreach(tllist, targetList)
  	{
  		TargetEntry *tle = (TargetEntry *) lfirst(tllist);
  		Oid			tletypid;
  		int32		tletypmod;
  		Form_pg_attribute attr;
  		char	   *attname;
  
  		/* resjunk entries may be ignored */
  		if (tle->resjunk)
  			continue;
  		i++;
  		if (i > resultDesc->natts)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  					 isSelect ?
  				   errmsg("SELECT rule's target list has too many entries") :
  					 errmsg("RETURNING list has too many entries")));
  
  		attr = resultDesc->attrs[i - 1];
  		attname = NameStr(attr->attname);
  
  		/*
  		 * Disallow dropped columns in the relation.  This is not really
  		 * expected to happen when creating an ON SELECT rule.  It'd be
  		 * possible if someone tried to convert a relation with dropped
  		 * columns to a view, but the only case we care about supporting
  		 * table-to-view conversion for is pg_dump, and pg_dump won't do that.
  		 *
  		 * Unfortunately, the situation is also possible when adding a rule
  		 * with RETURNING to a regular table, and rejecting that case is
  		 * altogether more annoying.  In principle we could support it by
  		 * modifying the targetlist to include dummy NULL columns
  		 * corresponding to the dropped columns in the tupdesc.  However,
  		 * places like ruleutils.c would have to be fixed to not process such
  		 * entries, and that would take an uncertain and possibly rather large
  		 * amount of work.  (Note we could not dodge that by marking the dummy
  		 * columns resjunk, since it's precisely the non-resjunk tlist columns
  		 * that are expected to correspond to table columns.)
  		 */
  		if (attr->attisdropped)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 isSelect ?
  					 errmsg("cannot convert relation containing dropped columns to view") :
  					 errmsg("cannot create a RETURNING list for a relation containing dropped columns")));
  
  		/* Check name match if required; no need for two error texts here */
  		if (requireColumnNameMatch && strcmp(tle->resname, attname) != 0)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  					 errmsg("SELECT rule's target entry %d has different column name from column \"%s\"",
  							i, attname),
  					 errdetail("SELECT target entry is named \"%s\".",
  							   tle->resname)));
  
  		/* Check type match. */
  		tletypid = exprType((Node *) tle->expr);
  		if (attr->atttypid != tletypid)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  					 isSelect ?
  					 errmsg("SELECT rule's target entry %d has different type from column \"%s\"",
  							i, attname) :
  					 errmsg("RETURNING list's entry %d has different type from column \"%s\"",
  							i, attname),
  					 isSelect ?
  					 errdetail("SELECT target entry has type %s, but column has type %s.",
  							   format_type_be(tletypid),
  							   format_type_be(attr->atttypid)) :
  					 errdetail("RETURNING list entry has type %s, but column has type %s.",
  							   format_type_be(tletypid),
  							   format_type_be(attr->atttypid))));
  
  		/*
  		 * Allow typmods to be different only if one of them is -1, ie,
  		 * "unspecified".  This is necessary for cases like "numeric", where
  		 * the table will have a filled-in default length but the select
  		 * rule's expression will probably have typmod = -1.
  		 */
  		tletypmod = exprTypmod((Node *) tle->expr);
  		if (attr->atttypmod != tletypmod &&
  			attr->atttypmod != -1 && tletypmod != -1)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  					 isSelect ?
  					 errmsg("SELECT rule's target entry %d has different size from column \"%s\"",
  							i, attname) :
  					 errmsg("RETURNING list's entry %d has different size from column \"%s\"",
  							i, attname),
  					 isSelect ?
  					 errdetail("SELECT target entry has type %s, but column has type %s.",
  							   format_type_with_typemod(tletypid, tletypmod),
  							   format_type_with_typemod(attr->atttypid,
  														attr->atttypmod)) :
  					 errdetail("RETURNING list entry has type %s, but column has type %s.",
  							   format_type_with_typemod(tletypid, tletypmod),
  							   format_type_with_typemod(attr->atttypid,
  														attr->atttypmod))));
  	}
  
  	if (i != resultDesc->natts)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  				 isSelect ?
  				 errmsg("SELECT rule's target list has too few entries") :
  				 errmsg("RETURNING list has too few entries")));
  }
  
  /*
   * setRuleCheckAsUser
   *		Recursively scan a query or expression tree and set the checkAsUser
   *		field to the given userid in all rtable entries.
   *
   * Note: for a view (ON SELECT rule), the checkAsUser field of the OLD
   * RTE entry will be overridden when the view rule is expanded, and the
   * checkAsUser field of the NEW entry is irrelevant because that entry's
   * requiredPerms bits will always be zero.  However, for other types of rules
   * it's important to set these fields to match the rule owner.  So we just set
   * them always.
   */
  void
  setRuleCheckAsUser(Node *node, Oid userid)
  {
  	(void) setRuleCheckAsUser_walker(node, &userid);
  }
  
  static bool
  setRuleCheckAsUser_walker(Node *node, Oid *context)
  {
  	if (node == NULL)
  		return false;
  	if (IsA(node, Query))
  	{
  		setRuleCheckAsUser_Query((Query *) node, *context);
  		return false;
  	}
  	return expression_tree_walker(node, setRuleCheckAsUser_walker,
  								  (void *) context);
  }
  
  static void
  setRuleCheckAsUser_Query(Query *qry, Oid userid)
  {
  	ListCell   *l;
  
  	/* Set all the RTEs in this query node */
  	foreach(l, qry->rtable)
  	{
  		RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
  
  		if (rte->rtekind == RTE_SUBQUERY)
  		{
  			/* Recurse into subquery in FROM */
  			setRuleCheckAsUser_Query(rte->subquery, userid);
  		}
  		else
  			rte->checkAsUser = userid;
  	}
  
  	/* Recurse into subquery-in-WITH */
  	foreach(l, qry->cteList)
  	{
  		CommonTableExpr *cte = (CommonTableExpr *) lfirst(l);
  
  		setRuleCheckAsUser_Query((Query *) cte->ctequery, userid);
  	}
  
  	/* If there are sublinks, search for them and process their RTEs */
  	if (qry->hasSubLinks)
  		query_tree_walker(qry, setRuleCheckAsUser_walker, (void *) &userid,
  						  QTW_IGNORE_RC_SUBQUERIES);
  }
  
  
  /*
   * Change the firing semantics of an existing rule.
   */
  void
  EnableDisableRule(Relation rel, const char *rulename,
  				  char fires_when)
  {
  	Relation	pg_rewrite_desc;
  	Oid			owningRel = RelationGetRelid(rel);
  	Oid			eventRelationOid;
  	HeapTuple	ruletup;
  	bool		changed = false;
  
  	/*
  	 * Find the rule tuple to change.
  	 */
  	pg_rewrite_desc = heap_open(RewriteRelationId, RowExclusiveLock);
  	ruletup = SearchSysCacheCopy2(RULERELNAME,
  								  ObjectIdGetDatum(owningRel),
  								  PointerGetDatum(rulename));
  	if (!HeapTupleIsValid(ruletup))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("rule \"%s\" for relation \"%s\" does not exist",
  						rulename, get_rel_name(owningRel))));
  
  	/*
  	 * Verify that the user has appropriate permissions.
  	 */
  	eventRelationOid = ((Form_pg_rewrite) GETSTRUCT(ruletup))->ev_class;
  	Assert(eventRelationOid == owningRel);
  	if (!pg_class_ownercheck(eventRelationOid, GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
  					   get_rel_name(eventRelationOid));
  
  	/*
  	 * Change ev_enabled if it is different from the desired new state.
  	 */
  	if (DatumGetChar(((Form_pg_rewrite) GETSTRUCT(ruletup))->ev_enabled) !=
  		fires_when)
  	{
  		((Form_pg_rewrite) GETSTRUCT(ruletup))->ev_enabled =
  			CharGetDatum(fires_when);
  		simple_heap_update(pg_rewrite_desc, &ruletup->t_self, ruletup);
  
  		/* keep system catalog indexes current */
  		CatalogUpdateIndexes(pg_rewrite_desc, ruletup);
  
  		changed = true;
  	}
  
  	InvokeObjectPostAlterHook(RewriteRelationId,
  							  HeapTupleGetOid(ruletup), 0);
  
  	heap_freetuple(ruletup);
  	heap_close(pg_rewrite_desc, RowExclusiveLock);
  
  	/*
  	 * If we changed anything, broadcast a SI inval message to force each
  	 * backend (including our own!) to rebuild relation's relcache entry.
  	 * Otherwise they will fail to apply the change promptly.
  	 */
  	if (changed)
  		CacheInvalidateRelcache(rel);
  }
  
  
  /*
   * Perform permissions and integrity checks before acquiring a relation lock.
   */
  static void
  RangeVarCallbackForRenameRule(const RangeVar *rv, Oid relid, Oid oldrelid,
  							  void *arg)
  {
  	HeapTuple	tuple;
  	Form_pg_class form;
  
  	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
  	if (!HeapTupleIsValid(tuple))
  		return;					/* concurrently dropped */
  	form = (Form_pg_class) GETSTRUCT(tuple);
  
  	/* only tables and views can have rules */
  	if (form->relkind != RELKIND_RELATION && form->relkind != RELKIND_VIEW)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a table or view", rv->relname)));
  
  	if (!allowSystemTableMods && IsSystemClass(relid, form))
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("permission denied: \"%s\" is a system catalog",
  						rv->relname)));
  
  	/* you must own the table to rename one of its rules */
  	if (!pg_class_ownercheck(relid, GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS, rv->relname);
  
  	ReleaseSysCache(tuple);
  }
  
  /*
   * Rename an existing rewrite rule.
   */
  ObjectAddress
  RenameRewriteRule(RangeVar *relation, const char *oldName,
  				  const char *newName)
  {
  	Oid			relid;
  	Relation	targetrel;
  	Relation	pg_rewrite_desc;
  	HeapTuple	ruletup;
  	Form_pg_rewrite ruleform;
  	Oid			ruleOid;
  	ObjectAddress address;
  
  	/*
  	 * Look up name, check permissions, and acquire lock (which we will NOT
  	 * release until end of transaction).
  	 */
  	relid = RangeVarGetRelidExtended(relation, AccessExclusiveLock,
  									 false, false,
  									 RangeVarCallbackForRenameRule,
  									 NULL);
  
  	/* Have lock already, so just need to build relcache entry. */
  	targetrel = relation_open(relid, NoLock);
  
  	/* Prepare to modify pg_rewrite */
  	pg_rewrite_desc = heap_open(RewriteRelationId, RowExclusiveLock);
  
  	/* Fetch the rule's entry (it had better exist) */
  	ruletup = SearchSysCacheCopy2(RULERELNAME,
  								  ObjectIdGetDatum(relid),
  								  PointerGetDatum(oldName));
  	if (!HeapTupleIsValid(ruletup))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("rule \"%s\" for relation \"%s\" does not exist",
  						oldName, RelationGetRelationName(targetrel))));
  	ruleform = (Form_pg_rewrite) GETSTRUCT(ruletup);
  	ruleOid = HeapTupleGetOid(ruletup);
  
  	/* rule with the new name should not already exist */
  	if (IsDefinedRewriteRule(relid, newName))
  		ereport(ERROR,
  				(errcode(ERRCODE_DUPLICATE_OBJECT),
  				 errmsg("rule \"%s\" for relation \"%s\" already exists",
  						newName, RelationGetRelationName(targetrel))));
  
  	/*
  	 * We disallow renaming ON SELECT rules, because they should always be
  	 * named "_RETURN".
  	 */
  	if (ruleform->ev_type == CMD_SELECT + '0')
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  				 errmsg("renaming an ON SELECT rule is not allowed")));
  
  	/* OK, do the update */
  	namestrcpy(&(ruleform->rulename), newName);
  
  	simple_heap_update(pg_rewrite_desc, &ruletup->t_self, ruletup);
  
  	/* keep system catalog indexes current */
  	CatalogUpdateIndexes(pg_rewrite_desc, ruletup);
  
  	heap_freetuple(ruletup);
  	heap_close(pg_rewrite_desc, RowExclusiveLock);
  
  	/*
  	 * Invalidate relation's relcache entry so that other backends (and this
  	 * one too!) are sent SI message to make them rebuild relcache entries.
  	 * (Ideally this should happen automatically...)
  	 */
  	CacheInvalidateRelcache(targetrel);
  
  	ObjectAddressSet(address, RewriteRelationId, ruleOid);
  
  	/*
  	 * Close rel, but keep exclusive lock!
  	 */
  	relation_close(targetrel, NoLock);
  
  	return address;
  }
  