Re: BUG #18467: postgres_fdw (deparser) ignores LimitOption

On Fri, 31 May 2024 at 16:22, Etsuro Fujita <etsuro.fujita@gmail.com> wrote:
> On Fri, May 31, 2024 at 10:12 AM Japin Li <japinli@hotmail.com> wrote:
>> I think I understand what you mean. We can ensure that the ORDER BY can be
>> safely pushed down if we are in add_foreign_final_paths().  The reason the
>> FETCH clause cannot be pushed down is only because the remote may not
>> support it, right?
>
> Yeah, I think so; for the next person, I would like to propose to
> update the comments proposed upthread to something like this:
>
>     /*
>      * If the query uses FETCH FIRST .. WITH TIES, 1) it must have ORDER BY as
>      * well, which is used to determine which additional rows tie for the last
>      * place in the result set, and 2) ORDER BY must already have been
>      * determined to be safe to push down before we get here.  So in that case
>      * the FETCH clause is safe to push down with ORDER BY if the remote
>      * server is v13 or later; but if not, the remote query will fail entirely
>      * for lack of support for it.  Since we do not currently have a way to do
>      * a remote-version check (without accessing the remote server), disable
>      * pushing it for now.
>      */
>
> Comments are welcome!
>

Thanks for the rewording!  LGTM.

--
Regrads,
Japin Li