Allow only some columns of a view to be auto-updateable.

Previously, unless all columns were auto-updateable, we wouldn't
inserts, updates, or deletes, or at least not without a rule or trigger;
now, we'll allow inserts and updates that target only the auto-updateable
columns, and deletes even if there are no auto-updateable columns at
all provided the view definition is otherwise suitable.

Dean Rasheed, reviewed by Marko Tiikkaja

doc/src/sgml/ref/create_view.sgml

@@ -319,16 +319,8 @@ CREATE VIEW vista AS SELECT text 'Hello World' AS hello;
 
      <listitem>
       <para>
-       All columns in the view's select list must be simple references to
-       columns of the underlying relation.  They cannot be expressions,
-       literals or functions.  System columns cannot be referenced, either.
-      </para>
-     </listitem>
-
-     <listitem>
-      <para>
-       No column of the underlying relation can appear more than once in
-       the view's select list.
+       The view's select list must not contain any aggregates, window functions
+       or set-returning functions.
       </para>
      </listitem>
 
@@ -340,6 +332,14 @@ CREATE VIEW vista AS SELECT text 'Hello World' AS hello;
     </itemizedlist>
    </para>
 
+   <para>
+    An automatically updatable view may contain a mix of updatable and
+    non-updatable columns.  A column is updatable if it is a simple reference
+    to an updatable column of the underlying base relation; otherwise the
+    column is read-only, and an error will be raised if an <command>INSERT</>
+    or <command>UPDATE</> statement attempts to assign a value to it.
+   </para>
+
    <para>
     If the view is automatically updatable the system will convert any
     <command>INSERT</>, <command>UPDATE</> or <command>DELETE</> statement
@@ -434,6 +434,25 @@ CREATE VIEW pg_comedies AS
    <literal>classification</> of new rows.
   </para>
 
+  <para>
+   Create a view with a mix of updatable and non-updatable columns:
+
+<programlisting>
+CREATE VIEW comedies AS
+    SELECT f.*,
+           country_code_to_name(f.country_code) AS country,
+           (SELECT avg(r.rating)
+            FROM user_ratings r
+            WHERE r.film_id = f.id) AS avg_rating
+    FROM films f
+    WHERE f.kind = 'Comedy';
+</programlisting>
+   This view will support <command>INSERT</>, <command>UPDATE</> and
+   <command>DELETE</>.  All the columns from the <literal>films</> table will
+   be updatable, whereas the computed columns <literal>country</> and
+   <literal>avg_rating</> will be read-only.
+  </para>
+
   <para>
    Create a recursive view consisting of the numbers from 1 to 100:
 <programlisting>

src/backend/commands/tablecmds.c

@@ -8806,7 +8806,8 @@ ATExecSetRelOptions(Relation rel, List *defList, AlterTableType operation,
 		if (check_option)
 		{   
 			const char *view_updatable_error =
-				view_query_is_auto_updatable(view_query, security_barrier);
+				view_query_is_auto_updatable(view_query,
+											 security_barrier, true);
 
 			if (view_updatable_error)
 				ereport(ERROR,

src/backend/commands/view.c

@@ -469,7 +469,7 @@ DefineView(ViewStmt *stmt, const char *queryString)
 	if (check_option)
 	{
 		const char *view_updatable_error =
-			view_query_is_auto_updatable(viewParse, security_barrier);
+			view_query_is_auto_updatable(viewParse, security_barrier, true);
 
 		if (view_updatable_error)
 			ereport(ERROR,

src/backend/utils/adt/misc.c

@@ -20,6 +20,7 @@
 #include <math.h>
 #include <unistd.h>
 
+#include "access/sysattr.h"
 #include "catalog/catalog.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_type.h"
@@ -540,17 +541,13 @@ pg_relation_is_updatable(PG_FUNCTION_ARGS)
 	Oid			reloid = PG_GETARG_OID(0);
 	bool		include_triggers = PG_GETARG_BOOL(1);
 
-	PG_RETURN_INT32(relation_is_updatable(reloid, include_triggers));
+	PG_RETURN_INT32(relation_is_updatable(reloid, include_triggers, NULL));
 }
 
 /*
  * pg_column_is_updatable - determine whether a column is updatable
  *
- * Currently we just check whether the column's relation is updatable.
- * Eventually we might allow views to have some updatable and some
- * non-updatable columns.
- *
- * Also, this function encapsulates the decision about just what
+ * This function encapsulates the decision about just what
  * information_schema.columns.is_updatable actually means.	It's not clear
  * whether deletability of the column's relation should be required, so
  * we want that decision in C code where we could change it without initdb.
@@ -560,6 +557,7 @@ pg_column_is_updatable(PG_FUNCTION_ARGS)
 {
 	Oid			reloid = PG_GETARG_OID(0);
 	AttrNumber	attnum = PG_GETARG_INT16(1);
+	AttrNumber	col = attnum - FirstLowInvalidHeapAttributeNumber;
 	bool		include_triggers = PG_GETARG_BOOL(2);
 	int			events;
 
@@ -567,7 +565,8 @@ pg_column_is_updatable(PG_FUNCTION_ARGS)
 	if (attnum <= 0)
 		PG_RETURN_BOOL(false);
 
-	events = relation_is_updatable(reloid, include_triggers);
+	events = relation_is_updatable(reloid, include_triggers,
+								   bms_make_singleton(col));
 
 	/* We require both updatability and deletability of the relation */
 #define REQ_EVENTS ((1 << CMD_UPDATE) | (1 << CMD_DELETE))

src/include/rewrite/rewriteHandler.h

@@ -22,9 +22,11 @@ extern void AcquireRewriteLocks(Query *parsetree, bool forUpdatePushedDown);
 
 extern Node *build_column_default(Relation rel, int attrno);
 extern Query *get_view_query(Relation view);
-extern const char *view_is_auto_updatable(Relation view);
 extern const char *view_query_is_auto_updatable(Query *viewquery,
-										 bool security_barrier);
-extern int	relation_is_updatable(Oid reloid, bool include_triggers);
+										 bool security_barrier,
+										 bool check_cols);
+extern int	relation_is_updatable(Oid reloid,
+						  bool include_triggers,
+						  Bitmapset *include_cols);
 
 #endif   /* REWRITEHANDLER_H */

src/test/regress/sql/updatable_views.sql

@@ -2,7 +2,8 @@
 -- UPDATABLE VIEWS
 --
 
--- check that non-updatable views are rejected with useful error messages
+-- check that non-updatable views and columns are rejected with useful error
+-- messages
 
 CREATE TABLE base_tbl (a int PRIMARY KEY, b text DEFAULT 'Unspecified');
 INSERT INTO base_tbl SELECT i, 'Row ' || i FROM generate_series(-2, 2) g(i);
@@ -20,31 +21,33 @@ CREATE VIEW ro_view10 AS SELECT 1 AS a; -- No base relations
 CREATE VIEW ro_view11 AS SELECT b1.a, b2.b FROM base_tbl b1, base_tbl b2; -- Multiple base relations
 CREATE VIEW ro_view12 AS SELECT * FROM generate_series(1, 10) AS g(a); -- SRF in rangetable
 CREATE VIEW ro_view13 AS SELECT a, b FROM (SELECT * FROM base_tbl) AS t; -- Subselect in rangetable
-CREATE VIEW ro_view14 AS SELECT ctid FROM base_tbl; -- System columns not supported
-CREATE VIEW ro_view15 AS SELECT a, upper(b) FROM base_tbl; -- Expression/function in targetlist
-CREATE VIEW ro_view16 AS SELECT a, b, a AS aa FROM base_tbl; -- Repeated column
+CREATE VIEW rw_view14 AS SELECT ctid, a, b FROM base_tbl; -- System columns may be part of an updatable view
+CREATE VIEW rw_view15 AS SELECT a, upper(b) FROM base_tbl; -- Expression/function may be part of an updatable view
+CREATE VIEW rw_view16 AS SELECT a, b, a AS aa FROM base_tbl; -- Repeated column may be part of an updatable view
 CREATE VIEW ro_view17 AS SELECT * FROM ro_view1; -- Base relation not updatable
 CREATE VIEW ro_view18 WITH (security_barrier = true)
   AS SELECT * FROM base_tbl; -- Security barrier views not updatable
 CREATE VIEW ro_view19 AS SELECT * FROM (VALUES(1)) AS tmp(a); -- VALUES in rangetable
 CREATE SEQUENCE seq;
 CREATE VIEW ro_view20 AS SELECT * FROM seq; -- View based on a sequence
+CREATE VIEW ro_view21 AS SELECT a, b, generate_series(1, a) g FROM base_tbl; -- SRF in targetlist not supported
 
 SELECT table_name, is_insertable_into
   FROM information_schema.tables
- WHERE table_name LIKE 'ro_view%'
+ WHERE table_name LIKE E'r_\\_view%'
  ORDER BY table_name;
 
 SELECT table_name, is_updatable, is_insertable_into
   FROM information_schema.views
- WHERE table_name LIKE 'ro_view%'
+ WHERE table_name LIKE E'r_\\_view%'
  ORDER BY table_name;
 
 SELECT table_name, column_name, is_updatable
   FROM information_schema.columns
- WHERE table_name LIKE 'ro_view%'
+ WHERE table_name LIKE E'r_\\_view%'
  ORDER BY table_name, ordinal_position;
 
+-- Read-only views
 DELETE FROM ro_view1;
 DELETE FROM ro_view2;
 DELETE FROM ro_view3;
@@ -58,13 +61,36 @@ UPDATE ro_view10 SET a=a+1;
 UPDATE ro_view11 SET a=a+1;
 UPDATE ro_view12 SET a=a+1;
 INSERT INTO ro_view13 VALUES (3, 'Row 3');
-INSERT INTO ro_view14 VALUES (null);
-INSERT INTO ro_view15 VALUES (3, 'ROW 3');
-INSERT INTO ro_view16 VALUES (3, 'Row 3', 3);
+-- Partially updatable view
+INSERT INTO rw_view14 VALUES (null, 3, 'Row 3'); -- should fail
+INSERT INTO rw_view14 (a, b) VALUES (3, 'Row 3'); -- should be OK
+UPDATE rw_view14 SET ctid=null WHERE a=3; -- should fail
+UPDATE rw_view14 SET b='ROW 3' WHERE a=3; -- should be OK
+SELECT * FROM base_tbl;
+DELETE FROM rw_view14 WHERE a=3; -- should be OK
+-- Partially updatable view
+INSERT INTO rw_view15 VALUES (3, 'ROW 3'); -- should fail
+INSERT INTO rw_view15 (a) VALUES (3); -- should be OK
+ALTER VIEW rw_view15 ALTER COLUMN upper SET DEFAULT 'NOT SET';
+INSERT INTO rw_view15 (a) VALUES (4); -- should fail
+UPDATE rw_view15 SET upper='ROW 3' WHERE a=3; -- should fail
+UPDATE rw_view15 SET upper=DEFAULT WHERE a=3; -- should fail
+UPDATE rw_view15 SET a=4 WHERE a=3; -- should be OK
+SELECT * FROM base_tbl;
+DELETE FROM rw_view15 WHERE a=4; -- should be OK
+-- Partially updatable view
+INSERT INTO rw_view16 VALUES (3, 'Row 3', 3); -- should fail
+INSERT INTO rw_view16 (a, b) VALUES (3, 'Row 3'); -- should be OK
+UPDATE rw_view16 SET a=3, aa=-3 WHERE a=3; -- should fail
+UPDATE rw_view16 SET aa=-3 WHERE a=3; -- should be OK
+SELECT * FROM base_tbl;
+DELETE FROM rw_view16 WHERE a=-3; -- should be OK
+-- Read-only views
 INSERT INTO ro_view17 VALUES (3, 'ROW 3');
 INSERT INTO ro_view18 VALUES (3, 'ROW 3');
 DELETE FROM ro_view19;
 UPDATE ro_view20 SET max_value=1000;
+UPDATE ro_view21 SET b=upper(b);
 
 DROP TABLE base_tbl CASCADE;
 DROP VIEW ro_view10, ro_view12, ro_view19;
@@ -510,6 +536,68 @@ SELECT * FROM rw_view1;
 
 DROP TABLE base_tbl CASCADE;
 
+-- views with updatable and non-updatable columns
+
+CREATE TABLE base_tbl(a float);
+INSERT INTO base_tbl SELECT i/10.0 FROM generate_series(1,10) g(i);
+
+CREATE VIEW rw_view1 AS
+  SELECT ctid, sin(a) s, a, cos(a) c
+  FROM base_tbl
+  WHERE a != 0
+  ORDER BY abs(a);
+
+INSERT INTO rw_view1 VALUES (null, null, 1.1, null); -- should fail
+INSERT INTO rw_view1 (s, c, a) VALUES (null, null, 1.1); -- should fail
+INSERT INTO rw_view1 (a) VALUES (1.1) RETURNING a, s, c; -- OK
+UPDATE rw_view1 SET s = s WHERE a = 1.1; -- should fail
+UPDATE rw_view1 SET a = 1.05 WHERE a = 1.1 RETURNING s; -- OK
+DELETE FROM rw_view1 WHERE a = 1.05; -- OK
+
+CREATE VIEW rw_view2 AS
+  SELECT s, c, s/c t, a base_a, ctid
+  FROM rw_view1;
+
+INSERT INTO rw_view2 VALUES (null, null, null, 1.1, null); -- should fail
+INSERT INTO rw_view2(s, c, base_a) VALUES (null, null, 1.1); -- should fail
+INSERT INTO rw_view2(base_a) VALUES (1.1) RETURNING t; -- OK
+UPDATE rw_view2 SET s = s WHERE base_a = 1.1; -- should fail
+UPDATE rw_view2 SET t = t WHERE base_a = 1.1; -- should fail
+UPDATE rw_view2 SET base_a = 1.05 WHERE base_a = 1.1; -- OK
+DELETE FROM rw_view2 WHERE base_a = 1.05 RETURNING base_a, s, c, t; -- OK
+
+CREATE VIEW rw_view3 AS
+  SELECT s, c, s/c t, ctid
+  FROM rw_view1;
+
+INSERT INTO rw_view3 VALUES (null, null, null, null); -- should fail
+INSERT INTO rw_view3(s) VALUES (null); -- should fail
+UPDATE rw_view3 SET s = s; -- should fail
+DELETE FROM rw_view3 WHERE s = sin(0.1); -- should be OK
+SELECT * FROM base_tbl ORDER BY a;
+
+SELECT table_name, is_insertable_into
+  FROM information_schema.tables
+ WHERE table_name LIKE E'r_\\_view%'
+ ORDER BY table_name;
+
+SELECT table_name, is_updatable, is_insertable_into
+  FROM information_schema.views
+ WHERE table_name LIKE E'r_\\_view%'
+ ORDER BY table_name;
+
+SELECT table_name, column_name, is_updatable
+  FROM information_schema.columns
+ WHERE table_name LIKE E'r_\\_view%'
+ ORDER BY table_name, ordinal_position;
+
+SELECT events & 4 != 0 AS upd,
+       events & 8 != 0 AS ins,
+       events & 16 != 0 AS del
+  FROM pg_catalog.pg_relation_is_updatable('rw_view3'::regclass, false) t(events);
+
+DROP TABLE base_tbl CASCADE;
+
 -- inheritance tests
 
 CREATE TABLE base_tbl_parent (a int);
@@ -611,7 +699,7 @@ CREATE TABLE base_tbl (a int);
 CREATE VIEW rw_view1 AS SELECT * FROM base_tbl WITH CHECK OPTION;
 CREATE VIEW rw_view2 AS SELECT * FROM rw_view1 WHERE a > 0;
 CREATE VIEW rw_view3 AS SELECT * FROM rw_view2 WITH CHECK OPTION;
-SELECT * FROM information_schema.views WHERE table_name LIKE E'rw\_view_' ORDER BY table_name;
+SELECT * FROM information_schema.views WHERE table_name LIKE E'rw\\_view_' ORDER BY table_name;
 
 INSERT INTO rw_view1 VALUES (-1); -- ok
 INSERT INTO rw_view1 VALUES (1); -- ok