Re: Defer selection of asynchronous subplans until the executor initialization stage

On Mon, Aug 30, 2021 at 5:36 PM Andrey V. Lepikhov
<a.lepikhov@postgrespro.ru> wrote:
> On 8/23/21 2:18 PM, Etsuro Fujita wrote:
> > To just execute what was planned at execution time, I think we should
> > return to the patch in [1].  The patch was created for Horiguchi-san’s
> > async-execution patch, so I modified it to work with HEAD, and added a
> > simplified version of your test cases.  Please find attached a patch.

> > [1] https://www.postgresql.org/message-id/7fe10f95-ac6c-c81d-a9d3-227493eb9055@postgrespro.ru

> I agree, this way is more safe. I tried to search for another approach,
> because here isn't general solution: for each plan node we should
> implement support of asynchronous behaviour.

I think so too.

> But for practical use, for small set of nodes, it will work good. I
> haven't any objections for this patch.

OK

To allow async execution in a bit more cases, I modified the patch a
bit further: a ProjectionPath put directly above an async-capable
ForeignPath would also be considered async-capable as ForeignScan can
project and no separate Result is needed in that case, so I modified
mark_async_capable_plan() as such, and added test cases to the
postgres_fdw regression test.  Attached is an updated version of the
patch.

Thanks for the review!

Best regards,
Etsuro Fujita