Horton

Re: Asynchronous Append on postgres_fdw nodes.

Kyotaro Horiguchi <horikyota.ntt@gmail.com>

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From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: a.lepikhov@postgrespro.ru
Cc: etsuro.fujita@gmail.com, movead.li@highgo.ca, pgsql-hackers@lists.postgresql.org
Date: 2020-06-15T08:29:34Z
Lists: pgsql-hackers 
Thanks for testing, but..

At Mon, 15 Jun 2020 08:51:23 +0500, "Andrey V. Lepikhov" <a.lepikhov@postgrespro.ru> wrote in 
> The patch has a problem with partitionwise aggregates.
> 
> Asynchronous append do not allow the planner to use partial
> aggregates. Example you can see in attachment. I can't understand why:
> costs of partitionwise join are less.
> Initial script and explains of the query with and without the patch
> you can see in attachment.

I had more or less the same plan with the second one without the patch
(that is, vanilla master/HEAD, but used merge joins instead).

I'm not sure what prevented join pushdown, but the difference between
the two is whether the each partitionwise join is pushed down to
remote or not, That is hardly seems related to the async execution
patch.

Could you tell me how did you get the first plan?

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center

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.