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: 2017-04-04 01:09:37
Message-ID: 20170404.100937.253129064.horiguchi.kyotaro@lab.ntt.co.jp
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Hello,

At Fri, 31 Mar 2017 18:20:23 +0900, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote in <CAD21AoBN-Hsih7HEP8ey6NUwQgwYj0O7eMuaRtas-6+CyafOgA(at)mail(dot)gmail(dot)com>
> On Wed, Mar 29, 2017 at 12:46 PM, Kyotaro HORIGUCHI
> <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> > Hello, it would be too late but I'd like to propose this because
> > this cannot be back-patched.
> >
> >
> > In autovacuum logs, "%u skipped frozen" shows the number of pages
> > skipped by ALL_FROZEN only in aggressive vacuum.
> >
> > So users cannot tell whether '0 skipped-frozen' means a
> > non-agressive vacuum or no frozen-pages in an agressive vacuum.
> >
> > I think it is nice to have an indication whether the scan was
> > "agressive" or not in log output.
>
> Good idea. I also was thinking about this.

Thanks. Currently we cannot use "skipped-frozen" to see the
effect of ALL_FROZEN.

> > Like this,
> >
> >> LOG: automatic aggressive vacuum of table "template1.pg_catalog.pg_statistic": index scans: 0
> >
> > "0 skipped frozen" is uesless in non-aggressive vacuum but
> > removing it would be too-much. Inserting "aggressive" reduces
> > machine-readability so it might be better in another place. The
> > attached patch does the following.
> >
> >> LOG: automatic vacuum of table "postgres.public.pgbench_branches": mode: normal, index scans: 0
> >> LOG: automatic vacuum of table "postgres.public.pgbench_branches": mode: aggressive, index scans: 0
> >
>
> Should we add this even to the manual vacuum verbose message?

I forgot that. The patch adds the mode indication in the first
message of VACUUM VERBOSE.

| =# 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. Is it
better to be "freezing" or something?

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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