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

On Fri, 31 May 2024 at 16:22, Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com> wrote:
> On Fri, May 31, 2024 at 10:12 AM Japin Li <japinli(at)hotmail(dot)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