pg.ddx.io  pgsql-hackers@postgresql.org mailing list archive  

help / color / mirror / Atom feed
From: Andrey Lepikhov <a.lepikhov@postgrespro.ru>
To: Etsuro Fujita <etsuro.fujita@gmail.com>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: Justin Pryzby <pryzby@telsasoft.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Asynchronous Append on postgres_fdw nodes.
Date: Fri, 7 May 2021 15:35:50 +0500
Message-ID: <52d944ea-7d41-1d16-01b7-8d1edf5ea972@postgrespro.ru> (raw)
In-Reply-To: <CAPmGK17JTeGJtKrW_xeRtbXaPBBEQy3+AcOdqcrM0fnHGmJVsw@mail.gmail.com>
References: <CAPmGK14igABfEruPPh1X=9KnjY=LquRHQij48oATSo1vWr7yOg@mail.gmail.com>
	<CAPmGK15xtFk2gb9-2b24mFtYBVWoGkmCPFPkM9RHpKVXGLk=sw@mail.gmail.com>
	<CAPmGK178d9-+aFgYorOY4n0pZmZ55WpQ7i1JcCagovYzAh+ueg@mail.gmail.com>
	<20210331.101137.148208859959175708.horikyota.ntt@gmail.com>
	<CAPmGK17T9Swy2FHZk4AVVKNzRxVnd96PX-18DSC2jeDXWNiBoQ@mail.gmail.com>
	<CAPmGK1637W30Wx3MnrReewhafn6F_0J76mrJGoFXFnpPq4QfvA@mail.gmail.com>
	<CAPmGK17O6fMfX84wWfypLWAO4NvD4fgDhm--oyzZ97YP+TxckA@mail.gmail.com>
	<c9388cb7-8cfc-bc92-0d6a-b519e6099cb6@postgrespro.ru>
	<CAPmGK17JTeGJtKrW_xeRtbXaPBBEQy3+AcOdqcrM0fnHGmJVsw@mail.gmail.com>

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);
>>
>> But works for the query:
>>
>> SELECT *
>>     FROM (SELECT * FROM f1 UNION ALL SELECT * FROM f2) AS q1
>> WHERE a < 10;
>>
>> As far as I understand, this is not a hard limit.
> 
> I think so, but IMO I think this would be an improvement rather than a bug fix.
> 
>> 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.
> 
> Thanks for the patch!  IIUC, another approach to this would be the
> patch you proposed before [1].  Right?
Yes. I think, new solution will be better.

-- 
regards,
Andrey Lepikhov
Postgres Professional





view thread (130+ messages)  latest in thread

Message-ID: <52d944ea-7d41-1d16-01b7-8d1edf5ea972@postgrespro.ru>
Permalink:  ../52d944ea-7d41-1d16-01b7-8d1edf5ea972@postgrespro.ru/
Also on:    postgresql.org/message-id/52d944ea-7d41-1d16-01b7-8d1edf5ea972@postgrespro.ru

 · 

reply
Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: pgsql-hackers@postgresql.org
  Cc: a.lepikhov@postgrespro.ru, etsuro.fujita@gmail.com, horikyota.ntt@gmail.com, pryzby@telsasoft.com, pgsql-hackers@lists.postgresql.org
  Subject: Re: Asynchronous Append on postgres_fdw nodes.
  In-Reply-To: <52d944ea-7d41-1d16-01b7-8d1edf5ea972@postgrespro.ru>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox