On Sun, Apr 24, 2016 at 8:01 PM, Robert Haas <robertmh...@gmail.com> wrote:
> > Of course, we could make this value 1-based rather than 0-based, as > Peter Geoghegan suggested a while back. But as I think I said at the > time, I think that's more misleading than helpful. The leader > participates in the parallel plan, but typically does far less of the > work beneath the Gather node than the other nodes involved in the > query, often almost none. In short, the leader is special. > Pretending that it's just another process involved in the parallel > group isn't doing anyone a favor. > Does this apply to the extent that a value of 1 is likely worse than 0 since the leader is now tasked with accumulating but there is only one process actually working to provide the leader data? I'm inclined to accept max_parallel_workers where a value of 0 means no parallelism and the non-zero counts indicate the number of workers in addition to the required leader. Though that does suggest "additional" as a valid option. Something like "max_additional_workers". Just how overloaded is the term "worker". If worker is understood to mean "a process which implements execution of [part of] a query plan" the word additional leaves no ambiguity as to where the leader is accounted for. It does significantly reduce grep-ability though :( max_additional_parallel_workers... David J.