Re: Rename max_parallel_degree?

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Geoghegan <pg@heroku.com>
Cc: Josh berkus <josh@agliodbs.com>, Robert Haas <robertmhaas@gmail.com>, Noah Misch <noah@leadboat.com>, David Rowley <david.rowley@2ndquadrant.com>, Amit Kapila <amit.kapila16@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Magnus Hagander <magnus@hagander.net>, Bruce Momjian <bruce@momjian.us>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2016-05-31T18:08:57Z
Lists: pgsql-hackers
Peter Geoghegan <pg@heroku.com> writes:
> Even when the leader is consuming input from workers, that's still perhaps
> pegging one CPU core. So, it doesn't really invalidate what I said about
> the number of cores being the primary consideration.

Agreed, but if we think that people need to be thinking in those terms,
maybe the parameter should be "max_parallel_cores".

The alternate docs patch I just posted tries to deal with this by
describing max_parallel_workers as being the max number of worker
processes used to "assist" a parallel query.  That was terminology
already being used in one place, but not consistently.  If we use it
consistently, I think it would be sufficient to remind people that
they need to figure on one more core for the leader.

			regards, tom lane