Horton

Re: Asynchronous Append on postgres_fdw nodes.

Etsuro Fujita <etsuro.fujita@gmail.com>

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From: Etsuro Fujita <etsuro.fujita@gmail.com>
To: Andrey Lepikhov <a.lepikhov@postgrespro.ru>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>, Justin Pryzby <pryzby@telsasoft.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2021-05-07T16:05:47Z
Lists: pgsql-hackers 
On Fri, May 7, 2021 at 7:35 PM Andrey Lepikhov
<a.lepikhov@postgrespro.ru> wrote:
> On 6/5/21 14:11, Etsuro Fujita wrote:
> > On Tue, Apr 27, 2021 at 3:57 PM Andrey V. Lepikhov
> > <a.lepikhov@postgrespro.ru> wrote:
> >> One more question. Append choose async plans at the stage of the Append
> >> plan creation.
> >> Later, the planner performs some optimizations, such as eliminating
> >> trivial Subquery nodes. So, AsyncAppend is impossible in some
> >> situations, for example:
> >>
> >> (SELECT * FROM f1 WHERE a < 10)
> >>     UNION ALL
> >> (SELECT * FROM f2 WHERE a < 10);

> >> We can choose async
> >> subplans at the beginning of the execution stage.
> >> For a demo, I prepared the patch (see in attachment).
> >> It solves the problem and passes the regression tests.
> >
> > IIUC, another approach to this would be the
> > patch you proposed before [1].  Right?
> Yes. I think, new solution will be better.

Ok, will review.

I think it would be better to start a new thread for this, and add the
patch to the next CF so that it doesn’t get lost.

Best regards,
Etsuro Fujita

Commits

  1. Improve comments for trivial_subqueryscan().

  2. Disable asynchronous execution if using gating Result nodes.

  3. Allow asynchronous execution in more cases.

  4. Doc: Further update documentation for asynchronous execution.

  5. Fix rescanning of async-aware Append nodes.

  6. Doc: Update documentation for asynchronous execution.

  7. Fix EXPLAIN ANALYZE for async-capable nodes.

  8. Minor code cleanup in asynchronous execution support.

  9. Adjust input value to WaitEventSetWait() in ExecAppendAsyncEventWait().

  10. Add support for asynchronous execution.