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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 15:32:47 +0500
Message-ID: <a38bb206-8340-9528-5ef6-37de2d5cb1a3@postgrespro.ru> (raw)
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On 6/5/21 11:45, Etsuro Fujita wrote:
> On Tue, Apr 27, 2021 at 9:31 PM Etsuro Fujita <etsuro.fujita@gmail.com> wrote:
> The patch fixes the issue, but I don’t think it’s the right way to go,
> because it requires an extra ExecProcNode() call, which wouldn’t be
> efficient.  Also, the patch wouldn’t address another issue I noticed
> in EXPLAIN ANALYZE for async-capable nodes that the command wouldn’t
> measure the time spent in such nodes accurately.  For the case of
> async-capable node using postgres_fdw, it only measures the time spent
> in ExecProcNode() in ExecAsyncRequest()/ExecAsyncNotify(), missing the
> time spent in other things such as creating a cursor in
> ExecAsyncRequest().  :-(.  To address both issues, I’d like to propose
> the attached, in which I added instrumentation support to
> ExecAsyncRequest()/ExecAsyncConfigureWait()/ExecAsyncNotify().  I
> think this would not only address the reported issue more efficiently,
> but allow to collect timing for async-capable nodes more accurately.

Ok, I agree with the approach, but the next test case failed:

EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
SELECT * FROM (
	(SELECT * FROM f1) UNION ALL (SELECT * FROM f2)
) q1 LIMIT 100;
ERROR:  InstrUpdateTupleCount called on node not yet executed

Initialization script see in attachment.

-- 
regards,
Andrey Lepikhov
Postgres Professional

Attachments:

  [application/sql] t1.sql (1.3K, ../a38bb206-8340-9528-5ef6-37de2d5cb1a3@postgrespro.ru/2-t1.sql)
  download

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