Re: Report the number of skipped frozen pages by manual VACUUM

From: Yugo Nagata <nagata(at)sraoss(dot)co(dot)jp>
To: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
Cc: Jim Nasby <jim(dot)nasby(at)openscg(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Report the number of skipped frozen pages by manual VACUUM
Date: 2017-03-15 10:09:10
Message-ID: 20170315190910.b7e53239.nagata@sraoss.co.jp
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On Fri, 10 Mar 2017 20:08:42 +0900
Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:

> On Fri, Mar 10, 2017 at 3:58 PM, Jim Nasby <jim(dot)nasby(at)openscg(dot)com> wrote:
> > On 3/6/17 8:34 PM, Masahiko Sawada wrote:
> >>
> >> I don't think it can say "1 frozen pages" because the number of
> >> skipped pages according to visibility map is always more than 32
> >> (SKIP_PAGES_THRESHOLD).
> >
> >
> > That's just an artifact of how the VM currently works. I'm not a fan of
> > cross dependencies like that unless there's a pretty good reason.
>
> Thank you for the comment.
> Agreed. Attached fixed version patch.

It seems that it says "frozen pages" if pinskipped_pages is not zero,
rather than about frozenskipped_pages.

How about writing as below?

appendStringInfo(&buf, ngettext("Skipped %u page due to buffer pins, "
"Skipped %u pages due to buffer pins, ",
vacrelstats->pinskipped_pages),
vacrelstats->pinskipped_pages);
appendStringInfo(&buf, ngettext("%u frozen page.\n", "%u frozen pages.\n",
vacrelstats->frozenskipped_pages),
vacrelstats->frozenskipped_pages);

>
> > BTW, I think there's already a function that handles the pluralization for
> > you. IIRC it's one of the things you can add to an ereport() call.
>
> What is the function name?
>
> Regards,
>
> --
> Masahiko Sawada
> NIPPON TELEGRAPH AND TELEPHONE CORPORATION
> NTT Open Source Software Center

--
Yugo Nagata <nagata(at)sraoss(dot)co(dot)jp>

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