Horton

Re: Asynchronous Append on postgres_fdw nodes.

Konstantin Knizhnik <k.knizhnik@postgrespro.ru>

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From: Konstantin Knizhnik <k.knizhnik@postgrespro.ru>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>, pryzby@telsasoft.com
Cc: a.lepikhov@postgrespro.ru, etsuro.fujita@gmail.com, movead.li@highgo.ca, pgsql-hackers@lists.postgresql.org
Date: 2020-09-22T12:52:33Z
Lists: pgsql-hackers

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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@telsasoft.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.
>> https://commitfest.postgresql.org/29/2491/
> Thanks. This is rebased version.
>
> At Fri, 14 Aug 2020 13:29:16 +1200, Thomas Munro <thomas.munro@gmail.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.
>


Hi,
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: http://www.postgrespro.com
The Russian Postgres Company

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.