From: Tom Lane <tgl@sss.pgh.pa.us>
To: Josh berkus <josh@agliodbs.com>
cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
        Peter Geoghegan <pg@heroku.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>
Subject: Re: Rename max_parallel_degree?
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Comments: In-reply-to Josh berkus <josh@agliodbs.com>
	message dated "Tue, 31 May 2016 11:22:02 -0700"
Date: Tue, 31 May 2016 14:29:56 -0400
Message-ID: <22406.1464719396@sss.pgh.pa.us>
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Sender: pgsql-hackers-owner@postgresql.org

Josh berkus <josh@agliodbs.com> writes:
> One more consistency question: what's the effect of running out of
> max_parallel_workers?

ITYM max_worker_processes (ie, the cluster-wide pool size)?

> That is, say max_parallel_workers is set to 10, and 8 are already
> allocated.  If I ask for max_parallel_X = 4, how many cores to I use?

One of my reasons for liking max_parallel_workers is that you can sensibly
compare it to max_worker_processes to figure out how many workers you're
likely to get.  If you think in terms of "degree" it takes some additional
mental arithmetic to understand what will happen.

> Presumably the leader isn't counted towards max_parallel_workers?

Not under what I'm proposing.

			regards, tom lane


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