Re: show "aggressive" or not in autovacuum logs

From: Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
To: sawada(dot)mshk(at)gmail(dot)com
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: show "aggressive" or not in autovacuum logs
Date: 2017-08-28 09:26:09
Message-ID: 20170828.182609.242774468.horiguchi.kyotaro@lab.ntt.co.jp
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Hello,

Currently the message shows the '%d skipped-frozen' message but
it is insufficient to verify the true effect. This is a patch to
show mode as 'aggressive' or 'normal' in the closing message of
vacuum. %d frozen-skipped when 'aggressive mode' shows the true
effect of ALL_FROZEN.

I will add this patch to CF2017-09.

At Tue, 4 Apr 2017 20:29:38 +0900, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote in <CAD21AoBiw96efy+tynvMLFQWERfPnhO53B=XFW9yyzEJN-fNaA(at)mail(dot)gmail(dot)com>
> On Tue, Apr 4, 2017 at 10:09 AM, Kyotaro HORIGUCHI
> <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> > | =# vacuum freeze verbose it;
> > | INFO: vacuuming "public.it" in aggressive mode
> > | INFO: "it": found 0 removable, 0 nonremovable row versions in 0 out of 0 pages
> > ...
> > | Skipped 0 pages due to buffer pins, 0 frozen pages.
> >
> > I still feel a bit uneasy about the word "aggressive" here.
>
> I think we can use the word "aggressive" here since we already use the
> word "aggressive vacuum" in docs[1], but it might be easily
> misunderstood.
>
> [1] https://www.postgresql.org/docs/9.6/static/routine-vacuuming.html
>
> >Is it better to be "freezing" or something?
>
> An another idea can be something like "prevent wraparound". The
> autovaucum process doing aggressive vacuum appears in pg_stat_activity
> with the word ".... (to prevent wraparound)". This word might be more
> user friendly IMO.

Hmm. This appears to be in several form.

https://www.postgresql.org/docs/devel/static/sql-vacuum.html

> aggressive “freezing” of tuples. ... Aggressive freezing

https://www.postgresql.org/docs/devel/static/routine-vacuuming.html

> VACUUM will perform an aggressive vacuum,
> an anti-wraparound autovacuum

https://www.postgresql.org/docs/devel/static/runtime-config-client.html

> ACUUM performs an aggressive scan

ps title

>.... (to prevent wraparound)

The nearest common wording seems to be just aggressive (vacuum)
so I left it alone in the attached patch.

regards,

--
Kyotaro Horiguchi
NTT Open Source Software Center

Attachment Content-Type Size
0001-Show-aggressive-or-not-in-vacuum-messages.patch text/x-patch 2.0 KB

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