From: | "Constantin S(dot) Pan" <kvapen(at)gmail(dot)com> |
---|---|
To: | Peter Geoghegan <pg(at)heroku(dot)com> |
Cc: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Pgsql Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [WIP] speeding up GIN build with parallel workers |
Date: | 2016-03-16 09:55:39 |
Message-ID: | 20160316125539.01cd4fd9@ppg |
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Lists: | pgsql-hackers |
On Wed, 16 Mar 2016 02:43:47 -0700
Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> On Wed, Mar 16, 2016 at 2:25 AM, Constantin S. Pan <kvapen(at)gmail(dot)com>
> wrote:
> > The backend just waits for the results from the workers and merges
> > them (in case wnum > 0). So the 1-worker configuration should never
> > be used, because it is as sequential as the 0-worker, but adds data
> > transfer.
>
> This is why I wanted an easy way of atomically guaranteeing some
> number of workers (typically 2), or not using parallelism at all. I
> think the parallel worker API should offer a simple way to do that in
> cases like this, where having only 1 worker is never going to win.
Well, we can check the number of workers actually launched and revert
back to single backend way when there is less than 2 workers. Let me
code that in.
Regards,
Constantin S. Pan
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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