postgres_fdw: Disable batch insertion when there are WCO constraints.

When inserting a view referencing a foreign table that has WITH CHECK
OPTION constraints, in single-insert mode postgres_fdw retrieves the
data that was actually inserted on the remote side so that the WITH
CHECK OPTION constraints are enforced with the data locally, but in
batch-insert mode it cannot currently retrieve the data (except for the
row first inserted through the view), resulting in enforcing the WITH
CHECK OPTION constraints with the data passed from the core (except for
the first-inserted row), which led to incorrect results when inserting
into a view referencing a foreign table in which a remote BEFORE ROW
INSERT trigger changes the rows inserted through the view so that they
violate the view's WITH CHECK OPTION constraint.  Also, the query
inserting into the view caused an assertion failure in assert-enabled
builds.

Fix these by disabling batch insertion when inserting into such a view.

Back-patch to v14 where batch insertion was added.

Discussion: https://postgr.es/m/CAPmGK17LpbTZs4m4a_6THP54UBeK9fHvX8aVVA%2BC6yEZDZwQcg%40mail.gmail.com

1 files changed, 16 insertions, 0 deletions

diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 2a250ee6324..42735ae78a9 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -1505,6 +1505,14 @@ UPDATE rw_view SET b = b + 15;
 UPDATE rw_view SET b = b + 15; -- ok
 SELECT * FROM foreign_tbl;
 
+-- We don't allow batch insert when there are any WCO constraints
+ALTER SERVER loopback OPTIONS (ADD batch_size '10');
+EXPLAIN (VERBOSE, COSTS OFF)
+INSERT INTO rw_view VALUES (0, 15), (0, 5);
+INSERT INTO rw_view VALUES (0, 15), (0, 5); -- should fail
+SELECT * FROM foreign_tbl;
+ALTER SERVER loopback OPTIONS (DROP batch_size);
+
 DROP FOREIGN TABLE foreign_tbl CASCADE;
 DROP TRIGGER row_before_insupd_trigger ON base_tbl;
 DROP TABLE base_tbl;
@@ -1543,6 +1551,14 @@ UPDATE rw_view SET b = b + 15;
 UPDATE rw_view SET b = b + 15; -- ok
 SELECT * FROM foreign_tbl;
 
+-- We don't allow batch insert when there are any WCO constraints
+ALTER SERVER loopback OPTIONS (ADD batch_size '10');
+EXPLAIN (VERBOSE, COSTS OFF)
+INSERT INTO rw_view VALUES (0, 15), (0, 5);
+INSERT INTO rw_view VALUES (0, 15), (0, 5); -- should fail
+SELECT * FROM foreign_tbl;
+ALTER SERVER loopback OPTIONS (DROP batch_size);
+
 DROP FOREIGN TABLE foreign_tbl CASCADE;
 DROP TRIGGER row_before_insupd_trigger ON child_tbl;
 DROP TABLE parent_tbl CASCADE;