Hello,

Please consider the following test:

create database foo;
\c foo

create table foo_test ( a int );

\c postgres

create extension if not exists postgres_fdw;
create server foo_server foreign data wrapper postgres_fdw options ( dbname
 'foo' );
create user mapping for current_user server foo_server;

create foreign table foo_test ( a int not null) server foo_server;

-- insert should return error for because NOT NULL constraint on column a
postgres=# insert into foo_test values ( null );
INSERT 0 1

postgres=# select * from foo_test;
 a
---

(1 row)

-- clean up
drop foreign table foo_test;
drop server foo_server cascade;
\c postgres
drop database foo;


Analysis:

As per the PG documentation it says that foreign table do support the
NOT NULL, NULL and DEFAULT.

http://www.postgresql.org/docs/devel/static/sql-createforeigntable.html

But when I tried the NOT NULL constraint, its not working for the foreign
tables.
Looking at the code into ExecInsert(), for the foreign table missed to call
ExecConstraints(). I am not sure whether it is intentional that  we not
calling
ExecConstraints() in case of foreign server or its missed.
Do share your thought on this.

I quickly fix the issue by adding ExecConstraints() call for foreign table
and
now test behaving as expected. PFA patch for the same.

Regards,
Rushabh Lathia
www.EnterpriseDB.com
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 6f0f47e..240126c 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -229,6 +229,12 @@ ExecInsert(TupleTableSlot *slot,
 	else if (resultRelInfo->ri_FdwRoutine)
 	{
 		/*
+		 * Check the constraints of the tuple
+		 */
+		if (resultRelationDesc->rd_att->constr)
+			ExecConstraints(resultRelInfo, slot, estate);
+
+		/*
 		 * insert into foreign table: let the FDW do it
 		 */
 		slot = resultRelInfo->ri_FdwRoutine->ExecForeignInsert(estate,
-- 
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