Adding upstream version 15.4.upstream/15.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1050 insertions, 0 deletions

diff --git a/src/backend/rewrite/rewriteDefine.c b/src/backend/rewrite/rewriteDefine.c
new file mode 100644
index 0000000..a354969
--- /dev/null
+++ b/src/backend/rewrite/rewriteDefine.c
@@ -0,0 +1,1050 @@
+/*-------------------------------------------------------------------------
+ *
+ * rewriteDefine.c
+ *	  routines for defining a rewrite rule
+ *
+ * Portions Copyright (c) 1996-2022, 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/tableam.h"
+#include "access/transam.h"
+#include "access/xact.h"
+#include "catalog/catalog.h"
+#include "catalog/dependency.h"
+#include "catalog/heap.h"
+#include "catalog/namespace.h"
+#include "catalog/objectaccess.h"
+#include "catalog/pg_inherits.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"
+
+
+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(const 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 = table_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);
+
+		CatalogTupleUpdate(pg_rewrite_desc, &tup->t_self, tup);
+
+		ReleaseSysCache(oldtup);
+
+		rewriteObjectId = ((Form_pg_rewrite) GETSTRUCT(tup))->oid;
+		is_update = true;
+	}
+	else
+	{
+		rewriteObjectId = GetNewOidWithIndex(pg_rewrite_desc,
+											 RewriteOidIndexId,
+											 Anum_pg_rewrite_oid);
+		values[Anum_pg_rewrite_oid - 1] = ObjectIdGetDatum(rewriteObjectId);
+
+		tup = heap_form_tuple(pg_rewrite_desc->rd_att, values, nulls);
+
+		CatalogTupleInsert(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 = linitial_node(Query, action);
+
+		qry = getInsertSelectQuery(qry, NULL);
+		recordDependencyOnExpr(&myself, event_qual, qry->rtable,
+							   DEPENDENCY_NORMAL);
+	}
+
+	/* Post creation hook for new rule */
+	InvokeObjectPostCreateHook(RewriteRelationId, rewriteObjectId, 0);
+
+	table_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(const 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 = table_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 &&
+		event_relation->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("relation \"%s\" cannot have rules",
+						RelationGetRelationName(event_relation)),
+				 errdetail_relkind_not_supported(event_relation->rd_rel->relkind)));
+
+	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, get_relkind_objtype(event_relation->rd_rel->relkind),
+					   RelationGetRelationName(event_relation));
+
+	/*
+	 * No rule actions that modify OLD or NEW
+	 */
+	foreach(l, action)
+	{
+		query = lfirst_node(Query, 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 = linitial_node(Query, action);
+		if (!is_instead ||
+			query->commandType != CMD_SELECT)
+			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 be
+		 * involved in partitioning, nor have any triggers, indexes, child or
+		 * parent tables, RLS policies, or RLS enabled.  (Note: some of 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 an obsolete
+		 * 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)
+		{
+			TableScanDesc scanDesc;
+			Snapshot	snapshot;
+			TupleTableSlot *slot;
+
+			if (event_relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("cannot convert partitioned table \"%s\" to a view",
+								RelationGetRelationName(event_relation))));
+
+			/* only case left: */
+			Assert(event_relation->rd_rel->relkind == RELKIND_RELATION);
+
+			if (event_relation->rd_rel->relispartition)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("cannot convert partition \"%s\" to a view",
+								RelationGetRelationName(event_relation))));
+
+			snapshot = RegisterSnapshot(GetLatestSnapshot());
+			scanDesc = table_beginscan(event_relation, snapshot, 0, NULL);
+			slot = table_slot_create(event_relation, NULL);
+			if (table_scan_getnextslot(scanDesc, ForwardScanDirection, slot))
+				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))));
+			ExecDropSingleTupleTableSlot(slot);
+			table_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 (has_superclass(RelationGetRelid(event_relation)))
+				ereport(ERROR,
+						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+						 errmsg("could not convert table \"%s\" to a view because it has parent 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 = lfirst_node(Query, 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);
+		}
+
+		/*
+		 * And finally, if it's not an ON SELECT rule then it must *not* be
+		 * named _RETURN.  This prevents accidentally or maliciously replacing
+		 * a view's ON SELECT rule with some other kind of rule.
+		 */
+		if (strcmp(rulename, ViewSelectRuleName) == 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("non-view rule for \"%s\" must not be named \"%s\"",
+							RelationGetRelationName(event_relation),
+							ViewSelectRuleName)));
+	}
+
+	/*
+	 * 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 = table_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->relam = InvalidOid;
+		classForm->reltablespace = InvalidOid;
+		classForm->relpages = 0;
+		classForm->reltuples = -1;
+		classForm->relallvisible = 0;
+		classForm->reltoastrelid = InvalidOid;
+		classForm->relhasindex = false;
+		classForm->relkind = RELKIND_VIEW;
+		classForm->relfrozenxid = InvalidTransactionId;
+		classForm->relminmxid = InvalidMultiXactId;
+		classForm->relreplident = REPLICA_IDENTITY_NOTHING;
+
+		CatalogTupleUpdate(relationRelation, &classTup->t_self, classTup);
+
+		heap_freetuple(classTup);
+		table_close(relationRelation, RowExclusiveLock);
+	}
+
+	ObjectAddressSet(address, RewriteRelationId, ruleId);
+
+	/* Close rel, but keep lock till commit... */
+	table_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 = TupleDescAttr(resultDesc, 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(castNode(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;
+	Form_pg_rewrite ruleform;
+	bool		changed = false;
+
+	/*
+	 * Find the rule tuple to change.
+	 */
+	pg_rewrite_desc = table_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))));
+
+	ruleform = (Form_pg_rewrite) GETSTRUCT(ruletup);
+
+	/*
+	 * Verify that the user has appropriate permissions.
+	 */
+	eventRelationOid = ruleform->ev_class;
+	Assert(eventRelationOid == owningRel);
+	if (!pg_class_ownercheck(eventRelationOid, GetUserId()))
+		aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(eventRelationOid)),
+					   get_rel_name(eventRelationOid));
+
+	/*
+	 * Change ev_enabled if it is different from the desired new state.
+	 */
+	if (DatumGetChar(ruleform->ev_enabled) !=
+		fires_when)
+	{
+		ruleform->ev_enabled = CharGetDatum(fires_when);
+		CatalogTupleUpdate(pg_rewrite_desc, &ruletup->t_self, ruletup);
+
+		changed = true;
+	}
+
+	InvokeObjectPostAlterHook(RewriteRelationId, ruleform->oid, 0);
+
+	heap_freetuple(ruletup);
+	table_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 &&
+		form->relkind != RELKIND_PARTITIONED_TABLE)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("relation \"%s\" cannot have rules", rv->relname),
+				 errdetail_relkind_not_supported(form->relkind)));
+
+	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, get_relkind_objtype(get_rel_relkind(relid)), 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,
+									 0,
+									 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 = table_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 = ruleform->oid;
+
+	/* 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);
+
+	CatalogTupleUpdate(pg_rewrite_desc, &ruletup->t_self, ruletup);
+
+	InvokeObjectPostAlterHook(RewriteRelationId, ruleOid, 0);
+
+	heap_freetuple(ruletup);
+	table_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;
+}