Re: Asynchronous Append on postgres_fdw nodes.

From: Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>
To: Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, pryzby(at)telsasoft(dot)com
Cc: a(dot)lepikhov(at)postgrespro(dot)ru, etsuro(dot)fujita(at)gmail(dot)com, movead(dot)li(at)highgo(dot)ca, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Asynchronous Append on postgres_fdw nodes.
Date: 2020-09-22 12:52:33
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On 20.08.2020 10:36, Kyotaro Horiguchi wrote:
> At Wed, 19 Aug 2020 23:25:36 -0500, Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote in
>> On Thu, Jul 02, 2020 at 11:14:48AM +0900, Kyotaro Horiguchi wrote:
>>> As the result of a discussion with Fujita-san off-list, I'm going to
>>> hold off development until he decides whether mine or Thomas' is
>>> better.
>> The latest patch doesn't apply so I set as WoA.
> Thanks. This is rebased version.
> At Fri, 14 Aug 2020 13:29:16 +1200, Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote in
>> Either way, we definitely need patch 0001. One comment:
>> -CreateWaitEventSet(MemoryContext context, int nevents)
>> +CreateWaitEventSet(MemoryContext context, ResourceOwner res, int nevents)
>> I wonder if it's better to have it receive ResourceOwner like that, or
>> to have it capture CurrentResourceOwner. I think the latter is more
>> common in existing code.
> There's no existing WaitEventSets belonging to a resowner. So
> unconditionally capturing CurrentResourceOwner doesn't work well. I
> could pass a bool instead but that make things more complex.
> Come to think of "complex", ExecAsync stuff in this patch might be
> too-much for a short-term solution until executor overhaul, if it
> comes shortly. (the patch of mine here as a whole is like that,
> though..). The queueing stuff in postgres_fdw is, too.
> regards.

Looks like current implementation of asynchronous append incorrectly
handle LIMIT clause:

psql:append.sql:10: ERROR:  another command is already in progress
CONTEXT:  remote SQL command: CLOSE c1

Konstantin Knizhnik
Postgres Professional:
The Russian Postgres Company

Attachment Content-Type Size
append.sql application/sql 666 bytes

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