When WCOs are present, disable direct foreign table modification.

If the user modifies a view that has CHECK OPTIONs and this gets
translated into a modification to an underlying relation which happens
to be a foreign table, the check options should be enforced.  In the
normal code path, that was happening properly, but it was not working
properly for "direct" modification because the whole operation gets
pushed to the remote side in that case and we never have an option to
enforce the constraint against individual tuples.  Fix by disabling
direct modification when there is a need to enforce CHECK OPTIONs.

Etsuro Fujita, reviewed by Kyotaro Horiguchi and by me.

Discussion: http://postgr.es/m/f8a48f54-6f02-9c8a-5250-9791603171ee@lab.ntt.co.jp

2 files changed, 84 insertions, 0 deletions

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 5bb3d97401e..c19b3318c72 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -5894,6 +5894,66 @@ INSERT INTO ft1(c1, c2) VALUES(1111, 2);
 UPDATE ft1 SET c2 = c2 + 1 WHERE c1 = 1;
 ALTER FOREIGN TABLE ft1 DROP CONSTRAINT ft1_c2negative;
 -- ===================================================================
+-- test WITH CHECK OPTION constraints
+-- ===================================================================
+CREATE TABLE base_tbl (a int, b int);
+CREATE FOREIGN TABLE foreign_tbl (a int, b int)
+  SERVER loopback OPTIONS(table_name 'base_tbl');
+CREATE VIEW rw_view AS SELECT * FROM foreign_tbl
+  WHERE a < b WITH CHECK OPTION;
+\d+ rw_view
+                           View "public.rw_view"
+ Column |  Type   | Collation | Nullable | Default | Storage | Description 
+--------+---------+-----------+----------+---------+---------+-------------
+ a      | integer |           |          |         | plain   | 
+ b      | integer |           |          |         | plain   | 
+View definition:
+ SELECT foreign_tbl.a,
+    foreign_tbl.b
+   FROM foreign_tbl
+  WHERE foreign_tbl.a < foreign_tbl.b;
+Options: check_option=cascaded
+
+INSERT INTO rw_view VALUES (0, 10); -- ok
+INSERT INTO rw_view VALUES (10, 0); -- should fail
+ERROR:  new row violates check option for view "rw_view"
+DETAIL:  Failing row contains (10, 0).
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE rw_view SET b = 20 WHERE a = 0; -- not pushed down
+                                            QUERY PLAN                                            
+--------------------------------------------------------------------------------------------------
+ Update on public.foreign_tbl
+   Remote SQL: UPDATE public.base_tbl SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.foreign_tbl
+         Output: foreign_tbl.a, 20, foreign_tbl.ctid
+         Remote SQL: SELECT a, ctid FROM public.base_tbl WHERE ((a < b)) AND ((a = 0)) FOR UPDATE
+(5 rows)
+
+UPDATE rw_view SET b = 20 WHERE a = 0; -- ok
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE rw_view SET b = -20 WHERE a = 0; -- not pushed down
+                                            QUERY PLAN                                            
+--------------------------------------------------------------------------------------------------
+ Update on public.foreign_tbl
+   Remote SQL: UPDATE public.base_tbl SET b = $2 WHERE ctid = $1
+   ->  Foreign Scan on public.foreign_tbl
+         Output: foreign_tbl.a, '-20'::integer, foreign_tbl.ctid
+         Remote SQL: SELECT a, ctid FROM public.base_tbl WHERE ((a < b)) AND ((a = 0)) FOR UPDATE
+(5 rows)
+
+UPDATE rw_view SET b = -20 WHERE a = 0; -- should fail
+ERROR:  new row violates check option for view "rw_view"
+DETAIL:  Failing row contains (0, -20).
+SELECT * FROM foreign_tbl;
+ a | b  
+---+----
+ 0 | 20
+(1 row)
+
+DROP FOREIGN TABLE foreign_tbl CASCADE;
+NOTICE:  drop cascades to view rw_view
+DROP TABLE base_tbl;
+-- ===================================================================
 -- test serial columns (ie, sequence-based defaults)
 -- ===================================================================
 create table loc1 (f1 serial, f2 text);
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index bb92189b0e6..5f65d9d966c 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -1181,6 +1181,30 @@ UPDATE ft1 SET c2 = c2 + 1 WHERE c1 = 1;
 ALTER FOREIGN TABLE ft1 DROP CONSTRAINT ft1_c2negative;
 
 -- ===================================================================
+-- test WITH CHECK OPTION constraints
+-- ===================================================================
+
+CREATE TABLE base_tbl (a int, b int);
+CREATE FOREIGN TABLE foreign_tbl (a int, b int)
+  SERVER loopback OPTIONS(table_name 'base_tbl');
+CREATE VIEW rw_view AS SELECT * FROM foreign_tbl
+  WHERE a < b WITH CHECK OPTION;
+\d+ rw_view
+
+INSERT INTO rw_view VALUES (0, 10); -- ok
+INSERT INTO rw_view VALUES (10, 0); -- should fail
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE rw_view SET b = 20 WHERE a = 0; -- not pushed down
+UPDATE rw_view SET b = 20 WHERE a = 0; -- ok
+EXPLAIN (VERBOSE, COSTS OFF)
+UPDATE rw_view SET b = -20 WHERE a = 0; -- not pushed down
+UPDATE rw_view SET b = -20 WHERE a = 0; -- should fail
+SELECT * FROM foreign_tbl;
+
+DROP FOREIGN TABLE foreign_tbl CASCADE;
+DROP TABLE base_tbl;
+
+-- ===================================================================
 -- test serial columns (ie, sequence-based defaults)
 -- ===================================================================
 create table loc1 (f1 serial, f2 text);