| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| 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 13:54:13 |
| Message-ID: | 16476.1490622853@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
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.
regards, tom lane
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