From: | Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com> |
---|---|
To: | "Andrey V(dot) Lepikhov" <a(dot)lepikhov(at)postgrespro(dot)ru> |
Cc: | Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Asynchronous Append on postgres_fdw nodes. |
Date: | 2021-05-06 06:45:06 |
Message-ID: | CAPmGK17yjZg2ajhs3erpfOKj+sg6yZU_gwvaeOV+j8g2E2bdcA@mail.gmail.com |
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On Tue, Apr 27, 2021 at 9:31 PM Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com> wrote:
> On Mon, Apr 26, 2021 at 7:35 PM Andrey V. Lepikhov
> <a(dot)lepikhov(at)postgrespro(dot)ru> wrote:
> > Small mistake i found. If no tuple was received from a foreign
> > partition, explain shows that we never executed node.
> > The patch in the attachment fixes this.
>
> Will look into this.
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.
Best regards,
Etsuro Fujita
Attachment | Content-Type | Size |
---|---|---|
fix-EXPLAIN-ANALYZE-for-async-capable-nodes.patch | application/octet-stream | 12.9 KB |
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