Re: Assumptions about the number of parallel workers

From: Andres Freund <andres(at)anarazel(dot)de>
To: Antonin Houska <ah(at)cybertec(dot)at>, Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Assumptions about the number of parallel workers
Date: 2020-02-06 02:50:29
Message-ID: 20200206025029.zj7bx7nygtfr53hh@alap3.anarazel.de
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Hi,

On 2020-02-05 10:50:05 +0100, Antonin Houska wrote:
> I can't figure out why ExecGather/ExecGatherMerge do check whether num_workers
> is non-zero. I think the code would be a bit clearer if these tests were
> replaced with Assert() statements, as the attached patch does.

It's probably related to force_parallel_mode. With that we'll IIRC
generate gather nodes even if num_workers == 0.

Greetings,

Andres Freund

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