From: Tom Lane <tgl@sss.pgh.pa.us>
To: Bruce Momjian <bruce@momjian.us>
Cc: David G. Johnston <david.g.johnston@gmail.com>
Cc: yigongh@gmail.com
Cc: pgsql-docs@lists.postgresql.org
Subject: Re: The suggestion of reducing autovacuum_vacuum_cost_delay should be documented
Date: Tue, 12 May 2020 19:26:07 -0400
Message-ID: <23940.1589325967@sss.pgh.pa.us> (raw)
In-Reply-To: <20200512224520.GE4666@momjian.us>
References: <158927918783.656.11973436145559215458@wrigleys.postgresql.org>
<20200512214014.GD4666@momjian.us>
<20200512214101.GA21408@momjian.us>
<CAKFQuwY+RMFFM1Y44=2dpi_8TyTq_4yrLUG6VjWnzgQAhG6o7Q@mail.gmail.com>
<20200512224520.GE4666@momjian.us>
Bruce Momjian <bruce@momjian.us> writes:
> On Tue, May 12, 2020 at 03:38:16PM -0700, David G. Johnston wrote:
>> The proposal is to document in versions 9.4 to 11 that the recommended value
>> for the setting is 2ms while for reasons of continuity the default in these
>> versions is 20ms.
>> I don't really see any harm in it. Its not like the choice to reduce the value
>> was made because of new features introduced in 12 - it was a re-evaluation of a
>> 15 year old default.
> Well, we really need to have some general discussion about whether
> changing defaults in major releases should trigger a mention to change
> the defaults in back branches. This is something that would have to be
> discussed on the hackers list.
It's not immediately obvious that the new default value established in
version N is appropriate for version N-minus-several. Certainly, whatever
testing was done to justify the new default wouldn't have been done on old
versions; and there might have been relevant changes.
In short: nope, I'm not on board with blindly back-patching such
recommendations.
regards, tom lane
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To: pgsql-docs@postgresql.org
Cc: tgl@sss.pgh.pa.us, bruce@momjian.us, david.g.johnston@gmail.com, yigongh@gmail.com, pgsql-docs@lists.postgresql.org
Subject: Re: The suggestion of reducing autovacuum_vacuum_cost_delay should be documented
In-Reply-To: <23940.1589325967@sss.pgh.pa.us>
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