From: Bruce Momjian <bruce@momjian.us>
To: 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 18:45:20 -0400
Message-ID: <20200512224520.GE4666@momjian.us> (raw)
In-Reply-To: <CAKFQuwY+RMFFM1Y44=2dpi_8TyTq_4yrLUG6VjWnzgQAhG6o7Q@mail.gmail.com>
References: <158927918783.656.11973436145559215458@wrigleys.postgresql.org>
<20200512214014.GD4666@momjian.us>
<20200512214101.GA21408@momjian.us>
<CAKFQuwY+RMFFM1Y44=2dpi_8TyTq_4yrLUG6VjWnzgQAhG6o7Q@mail.gmail.com>
On Tue, May 12, 2020 at 03:38:16PM -0700, David G. Johnston wrote:
> On Tue, May 12, 2020 at 2:41 PM Bruce Momjian <bruce@momjian.us> wrote:
>
> On Tue, May 12, 2020 at 05:40:14PM -0400, Bruce Momjian wrote:
> > On Tue, May 12, 2020 at 10:26:27AM +0000, PG Doc comments form wrote:
> > > The following documentation comment has been logged on the website:
> > >
> > > Page: https://www.postgresql.org/docs/11/runtime-config-autovacuum.html
> > > Description:
> > >
> > > The `autovacuum_vacuum_cost_delay` setting changes to 2ms in PostgreSQL
> 12
> > > but in the old Postgresql version, the default setting is still 20ms. I
> > > would suggest adding a suggestion in the old document
> > > to lower the autovacuum_vacuum_cost_delay as:
> > >
> > > > The default value of autovacuum_vacuum_cost_delay is reduced to 2ms
> in
> > > PostgreSQL 12. Reducing the autovacuum_vacuum_cost_delay will make the
> > > autovacuum more aggressive and might reduce the vacuum cost for
> > > write-intensive workload on big table.
> >
> > Uh, we usually don't suggest new defaults in back branches.
>
> Basically, what I am saying is that if you want this, it would be a new
> behavior that would need general discussion.
>
>
>
> 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.
--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EnterpriseDB https://enterprisedb.com
+ As you are, so once was I. As I am, so you will be. +
+ Ancient Roman grave inscription +
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-docs@postgresql.org
Cc: 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: <20200512224520.GE4666@momjian.us>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox