Re: Rename max_parallel_degree?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Bruce Momjian <bruce(at)momjian(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Rename max_parallel_degree?
Date: 2016-04-24 18:23:43
Message-ID: 28117.1461522223@sss.pgh.pa.us
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Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Sat, Apr 23, 2016 at 11:58 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>> Why is the parallelism variable called "max_parallel_degree"? Is that a
>> descriptive name? What does "degree" mean? Why is it not called
>> "max_parallel_workers"?

> Because "degree of parallelism" is standard terminology, I guess.

FWIW, I agree with Bruce that using "degree" here is a poor choice.
It's an unnecessary dependence on technical terminology that many people
will not be familiar with.

> Also, consider that we have the related but actually sorta different
> GUC max_worker_processes. I think max_parallel_workers to control the
> per-query behavior and max_worker_processes to control the global
> system behavior would be confusing - those names are very close
> together.

Well, that just says that we'd better reconsider *both* of those names.
Frankly, neither of them is well chosen, and the fact that they currently
sound unrelated is a bug not a feature. What about something like
"max_overall_worker_processes" and "max_session_worker_processes"?

regards, tom lane

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