| From: | Peter Geoghegan <pg(at)heroku(dot)com> |
|---|---|
| To: | Josh berkus <josh(at)agliodbs(dot)com> |
| Cc: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Bruce Momjian <bruce(at)momjian(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Rename max_parallel_degree? |
| Date: | 2016-05-31 18:27:14 |
| Message-ID: | CAM3SWZTOWOLkJ9EbqUu0a87M9aydWmn11Mr83tzzOm25ELjB2Q@mail.gmail.com |
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On Tue, May 31, 2016 at 11:22 AM, Josh berkus <josh(at)agliodbs(dot)com> wrote:
>> I think we can hope that developers are going to be less confused about
>> that than users.
>
> Makes sense.
Maybe EXPLAIN doesn't have to use the term parallel worker at all. It
can instead use a slightly broader terminology, possibly including the
term "core".
> One more consistency question: what's the effect of running out of
> max_parallel_workers?
>
> That is, say max_parallel_workers is set to 10, and 8 are already
> allocated. If I ask for max_parallel_X = 4, how many cores to I use?
Well, it depends on the planner, of course. But when constrained only
by the availability of worker processes, then your example could use 3
cores -- the 2 remaining parallel workers, plus the leader itself.
> Presumably the leader isn't counted towards max_parallel_workers?
Exactly.
--
Peter Geoghegan
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