Re: postgres_fdw behaves oddly

(2014/11/18 18:37), Ashutosh Bapat wrote:
> On Tue, Nov 18, 2014 at 1:55 PM, Etsuro Fujita
> <fujita.etsuro@lab.ntt.co.jp <mailto:fujita.etsuro@lab.ntt.co.jp>> wrote:
>     (2014/11/17 19:54), Ashutosh Bapat wrote:

>         Here are comments for postgres_fdw-syscol patch.

>         Code
>         -------
>         1. Instead of a single liner comment "System columns can't be
>         sent to
>         remote.", it might be better to explain why system columns can't
>         be sent
>         to the remote.

>     Done.

> I would add " and foreign values do not make sense locally (except may
> be ctid clubbed with foreign server_id)" to make it more clear. But I
> will leave that for the commiter to decide.

OK.

>         3. Since there is already a testcase which triggered this particular
>         change, it will good, if we add that to regression in postgres_fdw.

>     Done.

> I think, a better case would be SELECT * FROM ft1 t1, pg_class t2 WHERE
> t1.tableoid = t2.oid. The condition makes sure that the tableoid in the
> row is same as the OID of the foreign table recorded in pg_class
> locally. And the EXPLAIN of the query which clearly shows that the
> tableoid column in not fetched from the foreign server.

I thought that test, but I didn't use it because I think we can't see 
(at least from the EXPLAIN) why the qual is not pushed down: the qual 
isn't pushed down possibly becasue the qual is considered as a *join* 
qual, not because the qual just cotains tableoid.  (Having said that, I 
think we can see if the qual isn't pushed down as a join qual for a 
parameterized plan, but ISTM it's worth complicating regression tests.)

> Once we resolve the other patch on this thread,  I think this item can
> be marked as ready for commiter from my side.

OK.  Thank you for the review.

Best regards,
Etsuro Fujita