Horton

Re: crashes due to setting max_parallel_workers=0

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Rushabh Lathia <rushabh.lathia@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, David Rowley <david.rowley@2ndquadrant.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2017-03-27T16:26:17Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> On Mon, Mar 27, 2017 at 9:54 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Since this has now come up twice, I suggest adding a comment there
>> that explains why we're intentionally ignoring max_parallel_workers.

> Good idea.  How about the attached?

WFM ... but seems like there should be some flavor of this statement
in the user-facing docs too (ie, "max_parallel_workers_per_gather >
max_parallel_workers is a bad idea unless you're trying to test what
happens when a plan can't get all the workers it planned for").  The
existing text makes some vague allusions suggesting that the two
GUCs might be interrelated, but I think it could be improved.

			regards, tom lane

Commits

  1. Avoid GatherMerge crash when there are no workers.