| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)heroku(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, 大塚憲司 <otsuka(dot)kenji(at)nttcom(dot)co(dot)jp>, pgsql-docs(at)postgresql(dot)org, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [DOCS] The number of bytes is stored in index_size of pgstatindex() ? |
| Date: | 2016-02-19 20:05:44 |
| Message-ID: | 20160219200544.GA137983@alvherre.pgsql |
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| Lists: | pgsql-docs pgsql-hackers |
Peter Geoghegan wrote:
> On Thu, Feb 18, 2016 at 4:53 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> there are usage patterns where half-dead pages might accumulate.
> >
> > Other than a usage pattern of "randomly SIGKILL backends every few
> > seconds", I don't see how that would happen.
>
> I meant where pages could accumulate without being recycled.
But those pages are supposed to be used as the index grows. So unless
they are forgotten by the FSM, they shouldn't accumulate. (Except where
the table doesn't grow but only shrinks, so there's no need for new
index pages, but I don't think that's an interesting case.)
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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