Horton

Re: crashes due to setting max_parallel_workers=0

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Rushabh Lathia <rushabh.lathia@gmail.com>
Cc: 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: 2017-03-27T11:59:27Z
Lists: pgsql-hackers 
On Mon, Mar 27, 2017 at 1:29 AM, Rushabh Lathia
<rushabh.lathia@gmail.com> wrote:
>
>> But it seems a bit futile to produce the parallel plan in the first place,
>> because with max_parallel_workers=0 we can't possibly get any parallel
>> workers ever. I wonder why compute_parallel_worker() only looks at
>> max_parallel_workers_per_gather, i.e. why shouldn't it do:
>>
>>    parallel_workers = Min(parallel_workers, max_parallel_workers);
>>
>> Perhaps this was discussed and is actually intentional, though.
>>
>
> Yes, I am not quite sure about this.

It was intentional.  See the last paragraph of

https://www.postgresql.org/message-id/CA%2BTgmoaMSn6a1780VutfsarCu0LCr%3DCO2yi4vLUo-JQbn4YuRA@mail.gmail.com

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

  1. Avoid GatherMerge crash when there are no workers.