Horton

Re: Asynchronous Append on postgres_fdw nodes.

Andrei Lepikhov <a.lepikhov@postgrespro.ru>

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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>, Justin Pryzby <pryzby@telsasoft.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2021-05-07T10:32:47Z
Lists: pgsql-hackers

Attachments

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

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.