On Tue, 16 Feb 2021 at 02:12, Fabio Pardi <f.pa...@portavita.eu> wrote: > > On 14/02/2021 22:16, Gavin Flower wrote: > > While I agree it might be good to be able specify the number of workers, > > sure it would be possible to derive a suitable default based on the number > > of effective processors available? > > I had the same problem and my conclusion was that it is not possible to go > above 8 cores because of Amdahl's law on parallel computing. More here: > https://en.wikipedia.org/wiki/Amdahl%27s_law
That would really depend on what the non-parallel part of the equation was. There are some plan shapes such as GROUP BY or aggregate queries with very few or just 1 group where the serial portion of the execution is very small indeed. David
