Thread: Re: Remove an unnecessary check on semijoin_target_ok() on postgres_fdw.c

Tender Wang писал(а) 2024-10-09 10:26:
> Hi,
>    When I debug FDW join pushdown codes, I found below codes in
> semijoin_target_ok():
>     if (bms_is_member(var->varno, innerrel->relids) &&
> 
>         !bms_is_member(var->varno, outerrel->relids))
> 
> As far as I know, if a var belongs to the innerrel of joinrel, it's
> not possible that it
> may belong to the outerrel. So if the bms_is_member(var->varno,
> innerrel->relids)
> returns TRUE, then !bms_is_member(var->varno, outerrel->relids) must
> be TRUE.
> If bms_is_member(var->varno, innerrel->relids) returns FALSE,
> !bms_is_member(var->varno, outerrel->relids) will not execute due to
> short circuit.
> 
> So I think we can remove the "!bms_is_member(var->varno,
> outerrel->relids)" from if.
> Any thoughts?

Hi.
Seems good to me.
-- 
Best regards,
Alexander Pyhalov,
Postgres Professional

On Fri, Nov 29, 2024 at 3:39 AM Tender Wang <tndrwang@gmail.com> wrote:
> Alexander Pyhalov <a.pyhalov@postgrespro.ru> 于2024年11月29日周五 00:02写道：
>>
>> Tender Wang писал(а) 2024-10-09 10:26:
>> > Hi,
>> >    When I debug FDW join pushdown codes, I found below codes in
>> > semijoin_target_ok():
>> >     if (bms_is_member(var->varno, innerrel->relids) &&
>> >
>> >         !bms_is_member(var->varno, outerrel->relids))
>> >
>> > As far as I know, if a var belongs to the innerrel of joinrel, it's
>> > not possible that it
>> > may belong to the outerrel. So if the bms_is_member(var->varno,
>> > innerrel->relids)
>> > returns TRUE, then !bms_is_member(var->varno, outerrel->relids) must
>> > be TRUE.
>> > If bms_is_member(var->varno, innerrel->relids) returns FALSE,
>> > !bms_is_member(var->varno, outerrel->relids) will not execute due to
>> > short circuit.
>> >
>> > So I think we can remove the "!bms_is_member(var->varno,
>> > outerrel->relids)" from if.
>> > Any thoughts?
>>
>> Hi.
>> Seems good to me.
>> --
>> Best regards,
>> Alexander Pyhalov,
>> Postgres Professional
>
>
> Thanks for looking at that.

Pushed.  But I've decided to keep the redundant check as an assertion.

------
Regards,
Alexander Korotkov
Supabase