From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Rushabh Lathia <rushabh(dot)lathia(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: crashes due to setting max_parallel_workers=0 |
Date: | 2017-03-27 15:51:05 |
Message-ID: | CA+TgmoZXZZtxrS-x5UWuB0ghA3or-dT=mVqcvnf+HOoq5jHjCQ@mail.gmail.com |
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On Mon, Mar 27, 2017 at 9:54 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Mon, Mar 27, 2017 at 1:29 AM, Rushabh Lathia
>> <rushabh(dot)lathia(at)gmail(dot)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.
>
>> It was intentional. See the last paragraph of
>> https://www.postgresql.org/message-id/CA%2BTgmoaMSn6a1780VutfsarCu0LCr%3DCO2yi4vLUo-JQbn4YuRA@mail.gmail.com
>
> Since this has now come up twice, I suggest adding a comment there
> that explains why we're intentionally ignoring max_parallel_workers.
Hey, imagine if the comments explained the logic behind the code!
Good idea. How about the attached?
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
Attachment | Content-Type | Size |
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add-worker-comment.patch | application/octet-stream | 937 bytes |
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