On Fri, Dec 5, 2014 at 8:43 PM, Stephen Frost <
sfrost@snowman.net> wrote:
>
> José,
>
> * José Luis Tallón (
jltallon@adv-solutions.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.