Re: [WIP] speeding up GIN build with parallel workers

From: Peter Geoghegan <pg(at)heroku(dot)com>
To: "Constantin S(dot) Pan" <kvapen(at)gmail(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 09:43:47
Message-ID: CAM3SWZQ2yvbxmEk0ZmXVAV8jjOe_e_bi6_zD24_QbSPgyFVEeQ@mail.gmail.com
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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.

--
Peter Geoghegan

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