| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Peter Geoghegan <pg(at)heroku(dot)com> |
| Cc: | Josh berkus <josh(at)agliodbs(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Bruce Momjian <bruce(at)momjian(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Rename max_parallel_degree? |
| Date: | 2016-05-31 18:08:57 |
| Message-ID: | 21507.1464718137@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Peter Geoghegan <pg(at)heroku(dot)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
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