| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: parallel.c is not marked as test covered |
| Date: | 2016-05-11 17:58:23 |
| Message-ID: | CA+TgmoaaMAv5jwTDFWWfwjg3rXx7BuFb4vNATHUywq2JJy6agw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, May 11, 2016 at 1:48 PM, David G. Johnston
<david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
> What happens when there are no workers available due to max_worker_processes
> already being assigned?
Then the leader runs the plan after all.
> Related question, if max_parallel_degree is >1 and "the requested number of
> workers may not actually be available at runtime" is true, does the degree
> of parallelism minimize at 1 worker + leader or will the leader simply run
> the query by itself?
If the leader can get no workers at all, it will simply run the query
by itself. Of course, it tries to get as many as it can.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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