CREATE OR REPLACE VIEW, CREATE OR REPLACE RULE.

Gavin Sherry, Neil Conway, and Tom Lane all got their hands dirty
on this one ...

src/backend/commands/view.c

@@ -6,43 +6,43 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- *	$Id: view.c,v 1.68 2002/08/30 19:23:19 tgl Exp $
+ *
+ * IDENTIFICATION
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/view.c,v 1.69 2002/09/02 02:13:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
 
-#include "access/xact.h"
+#include "access/heapam.h"
 #include "catalog/dependency.h"
-#include "catalog/heap.h"
 #include "catalog/namespace.h"
 #include "commands/tablecmds.h"
 #include "commands/view.h"
 #include "miscadmin.h"
 #include "nodes/makefuncs.h"
 #include "parser/parse_relation.h"
-#include "parser/parse_type.h"
 #include "rewrite/rewriteDefine.h"
 #include "rewrite/rewriteManip.h"
-#include "rewrite/rewriteRemove.h"
 #include "rewrite/rewriteSupport.h"
-#include "utils/syscache.h"
+#include "utils/acl.h"
+#include "utils/lsyscache.h"
 
 
 /*---------------------------------------------------------------------
  * DefineVirtualRelation
  *
- * Create the "view" relation.
+ * Create the "view" relation. `DefineRelation' does all the work,
- * `DefineRelation' does all the work, we just provide the correct
+ * we just provide the correct arguments ... at least when we're
- * arguments!
+ * creating a view.  If we're updating an existing view, we have to
- *
+ * work harder.
- * If the relation already exists, then 'DefineRelation' will abort
- * the xact...
  *---------------------------------------------------------------------
  */
 static Oid
-DefineVirtualRelation(const RangeVar *relation, List *tlist)
+DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace)
 {
+	Oid			viewOid,
+				namespaceId;
 	CreateStmt *createStmt = makeNode(CreateStmt);
 	List	   *attrList,
 			   *t;
@@ -52,7 +52,7 @@ DefineVirtualRelation(const RangeVar *relation, List *tlist)
 	 * the (non-junk) targetlist items from the view's SELECT list.
 	 */
 	attrList = NIL;
-	foreach(t, tlist)
+	foreach (t, tlist)
 	{
 		TargetEntry *entry = lfirst(t);
 		Resdom	   *res = entry->resdom;
@@ -82,6 +82,54 @@ DefineVirtualRelation(const RangeVar *relation, List *tlist)
 	if (attrList == NIL)
 		elog(ERROR, "attempted to define virtual relation with no attrs");
 
+	/*
+	 * Check to see if we want to replace an existing view.
+	 */
+	namespaceId = RangeVarGetCreationNamespace(relation);
+	viewOid = get_relname_relid(relation->relname, namespaceId);
+
+	if (OidIsValid(viewOid) && replace)
+	{
+		Relation	rel;
+		TupleDesc	descriptor;
+
+		/*
+		 * Yes.  Get exclusive lock on the existing view ...
+		 */
+		rel = relation_open(viewOid, AccessExclusiveLock);
+
+		/*
+		 * Make sure it *is* a view, and do permissions checks.
+		 */
+		if (rel->rd_rel->relkind != RELKIND_VIEW)
+			elog(ERROR, "%s is not a view",
+				 RelationGetRelationName(rel));
+
+		if (!pg_class_ownercheck(viewOid, GetUserId()))
+			aclcheck_error(ACLCHECK_NOT_OWNER, RelationGetRelationName(rel));
+
+		/*
+		 * Create a tuple descriptor to compare against the existing view,
+		 * and verify it matches.
+		 *
+		 * XXX the error message is a bit cheesy here: would be useful to
+		 * give a more specific complaint about the difference in the
+		 * descriptors.  No time for it at the moment though.
+		 */
+	    descriptor = BuildDescForRelation(attrList);
+		if (!equalTupleDescs(descriptor, rel->rd_att))
+			elog(ERROR, "Cannot change column set of existing view %s",
+				 RelationGetRelationName(rel));
+
+		/*
+		 * Seems okay, so return the OID of the pre-existing view.
+		 */
+		relation_close(rel, NoLock); /* keep the lock! */
+
+		return viewOid;
+	}
+	else
+	{
 		/*
 		 * now create the parameters for keys/inheritance etc. All of them are
 		 * nil...
@@ -93,13 +141,16 @@ DefineVirtualRelation(const RangeVar *relation, List *tlist)
 		createStmt->hasoids = false;
 	
 		/*
-	 * finally create the relation...
+		 * finally create the relation (this will error out if there's
+		 * an existing view, so we don't need more code to complain
+		 * if "replace" is false).
 		 */
 		return DefineRelation(createStmt, RELKIND_VIEW);
+	}
 }
 
 static RuleStmt *
-FormViewRetrieveRule(const RangeVar *view, Query *viewParse)
+FormViewRetrieveRule(const RangeVar *view, Query *viewParse, bool replace)
 {
 	RuleStmt   *rule;
 
@@ -114,12 +165,13 @@ FormViewRetrieveRule(const RangeVar *view, Query *viewParse)
 	rule->event = CMD_SELECT;
 	rule->instead = true;
 	rule->actions = makeList1(viewParse);
+	rule->replace = replace;
 
 	return rule;
 }
 
 static void
-DefineViewRules(const RangeVar *view, Query *viewParse)
+DefineViewRules(const RangeVar *view, Query *viewParse, bool replace)
 {
 	RuleStmt   *retrieve_rule;
 
@@ -129,10 +181,9 @@ DefineViewRules(const RangeVar *view, Query *viewParse)
 	RuleStmt   *delete_rule;
 #endif
 
-	retrieve_rule = FormViewRetrieveRule(view, viewParse);
+	retrieve_rule = FormViewRetrieveRule(view, viewParse, replace);
 
 #ifdef NOTYET
-
 	replace_rule = FormViewReplaceRule(view, viewParse);
 	append_rule = FormViewAppendRule(view, viewParse);
 	delete_rule = FormViewDeleteRule(view, viewParse);
@@ -221,16 +272,18 @@ UpdateRangeTableOfViewParse(Oid viewOid, Query *viewParse)
  *-------------------------------------------------------------------
  */
 void
-DefineView(const RangeVar *view, Query *viewParse)
+DefineView(const RangeVar *view, Query *viewParse, bool replace)
 {
 	Oid			viewOid;
 
 	/*
 	 * Create the view relation
 	 *
-	 * NOTE: if it already exists, the xact will be aborted.
+	 * NOTE: if it already exists and replace is false, the xact will 
+	 * be aborted.
 	 */
-	viewOid = DefineVirtualRelation(view, viewParse->targetList);
+
+	viewOid = DefineVirtualRelation(view, viewParse->targetList, replace);
 
 	/*
 	 * The relation we have just created is not visible to any other
@@ -248,7 +301,7 @@ DefineView(const RangeVar *view, Query *viewParse)
 	/*
 	 * Now create the rules associated with the view.
 	 */
-	DefineViewRules(view, viewParse);
+	DefineViewRules(view, viewParse, replace);
 }
 
 /*

src/backend/nodes/copyfuncs.c

@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.209 2002/08/31 22:10:43 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.210 2002/09/02 02:13:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2173,6 +2173,7 @@ _copyRuleStmt(RuleStmt *from)
 	Node_Copy(from, newnode, whereClause);
 	newnode->event = from->event;
 	newnode->instead = from->instead;
+	newnode->replace = from->replace;
 	Node_Copy(from, newnode, actions);
 
 	return newnode;
@@ -2238,6 +2239,7 @@ _copyViewStmt(ViewStmt *from)
 	Node_Copy(from, newnode, view);
 	Node_Copy(from, newnode, aliases);
 	Node_Copy(from, newnode, query);
+	newnode->replace = from->replace;
 
 	return newnode;
 }

src/backend/nodes/equalfuncs.c

@@ -20,7 +20,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.157 2002/08/31 22:10:43 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.158 2002/09/02 02:13:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1003,6 +1003,8 @@ _equalRuleStmt(RuleStmt *a, RuleStmt *b)
 		return false;
 	if (a->instead != b->instead)
 		return false;
+	if (a->replace != b->replace)
+		return false;
 	if (!equal(a->actions, b->actions))
 		return false;
 
@@ -1067,6 +1069,8 @@ _equalViewStmt(ViewStmt *a, ViewStmt *b)
 		return false;
 	if (!equal(a->query, b->query))
 		return false;
+	if (a->replace != b->replace)
+		return false;
 
 	return true;
 }

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.364 2002/08/29 00:17:04 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.365 2002/09/02 02:13:01 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -3346,18 +3346,19 @@ opt_column: COLUMN									{ $$ = COLUMN; }
  *
  *****************************************************************************/
 
-RuleStmt:	CREATE RULE name AS
+RuleStmt:	CREATE opt_or_replace RULE name AS
 			{ QueryIsRule=TRUE; }
 			ON event TO qualified_name where_clause
 			DO opt_instead RuleActionList
 				{
 					RuleStmt *n = makeNode(RuleStmt);
-					n->relation = $9;
+					n->replace = $2;
-					n->rulename = $3;
+					n->relation = $10;
-					n->whereClause = $10;
+					n->rulename = $4;
-					n->event = $7;
+					n->whereClause = $11;
-					n->instead = $12;
+					n->event = $8;
-					n->actions = $13;
+					n->instead = $13;
+					n->actions = $14;
 					$$ = (Node *)n;
 					QueryIsRule=FALSE;
 				}
@@ -3537,12 +3538,14 @@ opt_trans:	WORK									{}
  *
  *****************************************************************************/
 
-ViewStmt:	CREATE VIEW qualified_name opt_column_list AS SelectStmt
+ViewStmt:	CREATE opt_or_replace VIEW qualified_name opt_column_list 
+				AS SelectStmt
 				{
 					ViewStmt *n = makeNode(ViewStmt);
-					n->view = $3;
+					n->replace = $2;
-					n->aliases = $4;
+					n->view = $4;
-					n->query = (Query *) $6;
+					n->aliases = $5;
+					n->query = (Query *) $7;
 					$$ = (Node *)n;
 				}
 		;

src/backend/rewrite/rewriteDefine.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteDefine.c,v 1.77 2002/08/05 03:29:17 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteDefine.c,v 1.78 2002/09/02 02:13:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -48,24 +48,23 @@ InsertRule(char *rulname,
 		   AttrNumber evslot_index,
 		   bool evinstead,
 		   Node *event_qual,
-		   List *action)
+		   List *action,
+		   bool replace)
 {
 	char	   *evqual = nodeToString(event_qual);
 	char	   *actiontree = nodeToString((Node *) action);
 	int			i;
 	Datum		values[Natts_pg_rewrite];
 	char		nulls[Natts_pg_rewrite];
+	char		replaces[Natts_pg_rewrite];
 	NameData	rname;
 	Relation	pg_rewrite_desc;
-	TupleDesc	tupDesc;
+	HeapTuple	tup,
-	HeapTuple	tup;
+				oldtup;
 	Oid			rewriteObjectId;
 	ObjectAddress	myself,
 					referenced;
-
+	bool		is_update = false;
-	if (IsDefinedRewriteRule(eventrel_oid, rulname))
-		elog(ERROR, "Attempt to insert rule \"%s\" failed: already exists",
-			 rulname);
 
 	/*
 	 * Set up *nulls and *values arrays
@@ -83,22 +82,61 @@ InsertRule(char *rulname,
 	values[i++] = DirectFunctionCall1(textin, CStringGetDatum(actiontree));	/* ev_action */
 
 	/*
-	 * create a new pg_rewrite tuple
+	 * Ready to store new pg_rewrite tuple
 	 */
 	pg_rewrite_desc = heap_openr(RewriteRelationName, RowExclusiveLock);
 
-	tupDesc = pg_rewrite_desc->rd_att;
+	/*
+	 * Check to see if we are replacing an existing tuple
+	 */
+	oldtup = SearchSysCache(RULERELNAME,
+							ObjectIdGetDatum(eventrel_oid),
+							PointerGetDatum(rulname),
+							0, 0);
 
-	tup = heap_formtuple(tupDesc,
+	if (HeapTupleIsValid(oldtup))
-						 values,
+	{
-						 nulls);
+		if (!replace)
+			elog(ERROR,"Attempt to insert rule \"%s\" failed: already exists",
+				 rulname);
+
+		/*
+		 * When replacing, we don't need to replace every attribute
+		 */
+		MemSet(replaces, ' ', sizeof(replaces));
+		replaces[Anum_pg_rewrite_ev_attr - 1] = 'r';
+		replaces[Anum_pg_rewrite_ev_type - 1] = 'r';
+		replaces[Anum_pg_rewrite_is_instead - 1] = 'r';
+		replaces[Anum_pg_rewrite_ev_qual - 1] = 'r';
+		replaces[Anum_pg_rewrite_ev_action - 1] = 'r';
+
+		tup = heap_modifytuple(oldtup, 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_formtuple(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(RelationGetRelid(pg_rewrite_desc),
+								   rewriteObjectId);
+
 	/*
 	 * Install dependency on rule's relation to ensure it will go away
 	 * on relation deletion.  If the rule is ON SELECT, make the dependency
@@ -121,6 +159,7 @@ InsertRule(char *rulname,
 	 */
 	recordDependencyOnExpr(&myself, (Node *) action, NIL,
 						   DEPENDENCY_NORMAL);
+
 	if (event_qual != NULL)
 	{
 		/* Find query containing OLD/NEW rtable entries */
@@ -143,6 +182,7 @@ DefineQueryRewrite(RuleStmt *stmt)
 	Node	   *event_qual = stmt->whereClause;
 	CmdType		event_type = stmt->event;
 	bool		is_instead = stmt->instead;
+	bool		replace = stmt->replace;
 	List	   *action = stmt->actions;
 	Relation	event_relation;
 	Oid			ev_relid;
@@ -232,7 +272,7 @@ DefineQueryRewrite(RuleStmt *stmt)
 		 * event relation, ...
 		 */
 		i = 0;
-		foreach(tllist, query->targetList)
+		foreach (tllist, query->targetList)
 		{
 			TargetEntry *tle = (TargetEntry *) lfirst(tllist);
 			Resdom	   *resdom = tle->resdom;
@@ -282,7 +322,7 @@ DefineQueryRewrite(RuleStmt *stmt)
 		/*
 		 * ... there must not be another ON SELECT rule already ...
 		 */
-		if (event_relation->rd_rules != NULL)
+		if (!replace && event_relation->rd_rules != NULL)
 		{
 			for (i = 0; i < event_relation->rd_rules->numLocks; i++)
 			{
@@ -364,7 +404,8 @@ DefineQueryRewrite(RuleStmt *stmt)
 							event_attno,
 							is_instead,
 							event_qual,
-							action);
+							action,
+							replace);
 
 		/*
 		 * Set pg_class 'relhasrules' field TRUE for event relation. If

src/backend/tcop/utility.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/tcop/utility.c,v 1.175 2002/08/30 19:23:20 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/tcop/utility.c,v 1.176 2002/09/02 02:13:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -595,7 +595,7 @@ ProcessUtility(Node *parsetree,
 			{
 				ViewStmt   *stmt = (ViewStmt *) parsetree;
 
-				DefineView(stmt->view, stmt->query);
+				DefineView(stmt->view, stmt->query, stmt->replace);
 			}
 			break;
 

src/include/commands/view.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: view.h,v 1.16 2002/07/01 15:27:56 tgl Exp $
+ * $Id: view.h,v 1.17 2002/09/02 02:13:02 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -16,7 +16,7 @@
 
 #include "nodes/parsenodes.h"
 
-extern void DefineView(const RangeVar *view, Query *view_parse);
+extern void DefineView(const RangeVar *view, Query *view_parse, bool replace);
 extern void RemoveView(const RangeVar *view, DropBehavior behavior);
 
 #endif   /* VIEW_H */

src/include/nodes/parsenodes.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: parsenodes.h,v 1.204 2002/08/31 22:10:47 tgl Exp $
+ * $Id: parsenodes.h,v 1.205 2002/09/02 02:13:02 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1371,6 +1371,7 @@ typedef struct RuleStmt
 	CmdType		event;			/* SELECT, INSERT, etc */
 	bool		instead;		/* is a 'do instead'? */
 	List	   *actions;		/* the action statements */
+	bool		replace;		/* OR REPLACE */
 } RuleStmt;
 
 /* ----------------------
@@ -1436,6 +1437,7 @@ typedef struct ViewStmt
 	RangeVar   *view;			/* the view to be created */
 	List	   *aliases;		/* target column names */
 	Query	   *query;			/* the SQL statement */
+	bool		replace;		/* replace an existing view? */
 } ViewStmt;
 
 /* ----------------------

src/test/regress/expected/create_view.out

@@ -15,3 +15,43 @@ CREATE VIEW iexit AS
 CREATE VIEW toyemp AS
    SELECT name, age, location, 12*salary AS annualsal
    FROM emp;
+--
+-- CREATE OR REPLACE VIEW
+--
+CREATE TABLE viewtest_tbl (a int, b int);
+COPY viewtest_tbl FROM stdin;
+CREATE OR REPLACE VIEW viewtest AS
+	SELECT * FROM viewtest_tbl;
+CREATE OR REPLACE VIEW viewtest AS
+	SELECT * FROM viewtest_tbl WHERE a > 10;
+SELECT * FROM viewtest;
+ a  | b  
+----+----
+ 15 | 20
+ 20 | 25
+(2 rows)
+
+CREATE OR REPLACE VIEW viewtest AS
+	SELECT a, b FROM viewtest_tbl WHERE a > 5 ORDER BY b DESC;
+SELECT * FROM viewtest;
+ a  | b  
+----+----
+ 20 | 25
+ 15 | 20
+ 10 | 15
+(3 rows)
+
+-- should fail
+CREATE OR REPLACE VIEW viewtest AS
+	SELECT a FROM viewtest_tbl WHERE a <> 20;
+ERROR:  Cannot change column set of existing view viewtest
+-- should fail
+CREATE OR REPLACE VIEW viewtest AS
+	SELECT 1, * FROM viewtest_tbl;
+ERROR:  Cannot change column set of existing view viewtest
+-- should fail
+CREATE OR REPLACE VIEW viewtest AS
+	SELECT a, b::numeric FROM viewtest_tbl;
+ERROR:  Cannot change column set of existing view viewtest
+DROP VIEW viewtest;
+DROP TABLE viewtest_tbl;

src/test/regress/expected/rules.out

@@ -1343,3 +1343,21 @@ SELECT tablename, rulename, definition FROM pg_rules
  shoelace_ok   | shoelace_ok_ins | CREATE RULE shoelace_ok_ins AS ON INSERT TO shoelace_ok DO INSTEAD UPDATE shoelace SET sl_avail = (shoelace.sl_avail + new.ok_quant) WHERE (shoelace.sl_name = new.ok_name);
 (29 rows)
 
+--
+-- CREATE OR REPLACE RULE
+--
+CREATE TABLE ruletest_tbl (a int, b int);
+CREATE TABLE ruletest_tbl2 (a int, b int);
+CREATE OR REPLACE RULE myrule AS ON INSERT TO ruletest_tbl
+	DO INSTEAD INSERT INTO ruletest_tbl2 VALUES (10, 10);
+INSERT INTO ruletest_tbl VALUES (99, 99);
+CREATE OR REPLACE RULE myrule AS ON INSERT TO ruletest_tbl
+	DO INSTEAD INSERT INTO ruletest_tbl2 VALUES (1000, 1000);
+INSERT INTO ruletest_tbl VALUES (99, 99);
+SELECT * FROM ruletest_tbl2;
+  a   |  b   
+------+------
+   10 |   10
+ 1000 | 1000
+(2 rows)
+

src/test/regress/sql/create_view.sql

@@ -19,3 +19,42 @@ CREATE VIEW toyemp AS
    SELECT name, age, location, 12*salary AS annualsal
    FROM emp;
 
+--
+-- CREATE OR REPLACE VIEW
+--
+
+CREATE TABLE viewtest_tbl (a int, b int);
+COPY viewtest_tbl FROM stdin;
+5	10
+10	15
+15	20
+20	25
+\.
+
+CREATE OR REPLACE VIEW viewtest AS
+	SELECT * FROM viewtest_tbl;
+
+CREATE OR REPLACE VIEW viewtest AS
+	SELECT * FROM viewtest_tbl WHERE a > 10;
+
+SELECT * FROM viewtest;
+
+CREATE OR REPLACE VIEW viewtest AS
+	SELECT a, b FROM viewtest_tbl WHERE a > 5 ORDER BY b DESC;
+
+SELECT * FROM viewtest;
+
+-- should fail
+CREATE OR REPLACE VIEW viewtest AS
+	SELECT a FROM viewtest_tbl WHERE a <> 20;
+
+-- should fail
+CREATE OR REPLACE VIEW viewtest AS
+	SELECT 1, * FROM viewtest_tbl;
+
+-- should fail
+CREATE OR REPLACE VIEW viewtest AS
+	SELECT a, b::numeric FROM viewtest_tbl;
+
+DROP VIEW viewtest;
+DROP TABLE viewtest_tbl;

src/test/regress/sql/rules.sql

@@ -765,3 +765,21 @@ SELECT viewname, definition FROM pg_views ORDER BY viewname;
 SELECT tablename, rulename, definition FROM pg_rules 
 	ORDER BY tablename, rulename;
 
+--
+-- CREATE OR REPLACE RULE
+--
+
+CREATE TABLE ruletest_tbl (a int, b int);
+CREATE TABLE ruletest_tbl2 (a int, b int);
+
+CREATE OR REPLACE RULE myrule AS ON INSERT TO ruletest_tbl
+	DO INSTEAD INSERT INTO ruletest_tbl2 VALUES (10, 10);
+
+INSERT INTO ruletest_tbl VALUES (99, 99);
+
+CREATE OR REPLACE RULE myrule AS ON INSERT TO ruletest_tbl
+	DO INSTEAD INSERT INTO ruletest_tbl2 VALUES (1000, 1000);
+
+INSERT INTO ruletest_tbl VALUES (99, 99);
+
+SELECT * FROM ruletest_tbl2;