| From: | Stephen Frost <sfrost(at)snowman(dot)net> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Fabrízio Mello <fabriziomello(at)gmail(dot)com>, Thom Brown <thom(at)linux(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Parallel Seq Scan |
| Date: | 2015-01-11 10:27:22 |
| Message-ID: | 20150111102722.GR3062@tamriel.snowman.net |
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| Lists: | pgsql-hackers |
* Robert Haas (robertmhaas(at)gmail(dot)com) wrote:
> On Thu, Jan 8, 2015 at 2:46 PM, Stephen Frost <sfrost(at)snowman(dot)net> wrote:
> > Yeah, if we come up with a plan for X workers and end up not being able
> > to spawn that many then I could see that being worth a warning or notice
> > or something. Not sure what EXPLAIN has to do anything with it..
>
> That seems mighty odd to me. If there are 8 background worker
> processes available, and you allow each session to use at most 4, then
> when there are >2 sessions trying to do parallelism at the same time,
> they might not all get their workers. Emitting a notice for that
> seems like it would be awfully chatty.
Yeah, agreed, it could get quite noisy. Did you have another thought
for how to address the concern raised? Specifically, that you might not
get as many workers as you thought you would?
Thanks,
Stephen
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