| From: | Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com> |
|---|---|
| To: | Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Expression errors with "FOR UPDATE" and postgres_fdw with partition wise join enabled. |
| Date: | 2018-07-04 10:11:35 |
| Message-ID: | CAFjFpRfVwaxfrRi8u5LmBX-zMhyzwYdGcj2VzpoxKYWLm9Y91A@mail.gmail.com |
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On Wed, Jul 4, 2018 at 3:36 PM, Etsuro Fujita
<fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
>
> I don't produce a test case where the plan is an Append with Gather
> subplans, but I'm not sure that it's a good thing to allow us to consider
> such a plan because in that plan, each Gather would try to grab its own pool
> of workers. Am I missing something?
If the overall join can not use parallelism, having individual child
joins use parallel query might turn out to be efficient even if done
one child at a time. Parallel append drastically reduces the cases
where something like could be useful, but I don't think we can
theoretically eliminate the need for such a plan.
--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company
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