From: | Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Parallel Append implementation |
Date: | 2017-02-17 16:26:26 |
Message-ID: | CAJ3gD9dRuB2A9zDQT5WH8_Ed+nP1Q9P_1s_OSZhp91xmafV8uQ@mail.gmail.com |
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On 16 February 2017 at 20:37, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> I'm not sure that it's going to be useful to make this logic very
> complicated. I think the most important thing is to give 1 worker to
> each plan before we give a second worker to any plan. In general I
> think it's sufficient to assign a worker that becomes available to the
> subplan with the fewest number of workers (or one of them, if there's
> a tie)
> without worrying too much about the target number of workers for that subplan.
The reason I have considered per-subplan workers is , for instance, so
that we can respect the parallel_workers reloption set by the user for
different tables. Or for e.g., subquery1 is a big hash join needing
more workers, and subquery2 is a small table requiring quite lesser
workers, it seems to make sense to give more workers to subquery1.
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