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 :(


David J.

Reply via email to