From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
---|---|
To: | Stephen Frost <sfrost(at)snowman(dot)net> |
Cc: | José Luis Tallón <jltallon(at)adv-solutions(dot)net>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Parallel Seq Scan |
Date: | 2014-12-06 06:41:53 |
Message-ID: | CAA4eK1Lr6JxwfBufaJSuHm1PpYYE9oM-U0e1tpk7itmmowh+zA@mail.gmail.com |
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On Fri, Dec 5, 2014 at 8:43 PM, Stephen Frost <sfrost(at)snowman(dot)net> wrote:
>
> José,
>
> * José Luis Tallón (jltallon(at)adv-solutions(dot)net) wrote:
> > On 12/04/2014 07:35 AM, Amit Kapila wrote:
> > >The number of worker backends that can be used for
> > >parallel seq scan can be configured by using a new GUC
> > >parallel_seqscan_degree, the default value of which is zero
> > >and it means parallel seq scan will not be considered unless
> > >user configures this value.
> >
> > The number of parallel workers should be capped (of course!) at the
> > maximum amount of "processors" (cores/vCores, threads/hyperthreads)
> > available.
> >
> > More over, when load goes up, the relative cost of parallel working
> > should go up as well.
> > Something like:
> > p = number of cores
> > l = 1min-load
> >
> > additional_cost = tuple estimate * cpu_tuple_cost * (l+1)/(c-1)
> >
> > (for c>1, of course)
>
> While I agree in general that we'll need to come up with appropriate
> acceptance criteria, etc, I don't think we want to complicate this patch
> with that initially.
>
>A SUSET GUC which caps the parallel GUC would be
> enough for an initial implementation, imv.
>
This is exactly what I have done in patch.
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com
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