Re: pg_database_size differs from df -s

On Wed, 2012-06-06 at 18:46 +0200, Julien Rouhaud wrote:
> On Wed, Jun 6, 2012 at 6:28 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> > Frank Lanitz <frank(at)frank(dot)uvena(dot)de> writes:
> > > Am 06.06.2012 17:49, schrieb Tom Lane:
> > >> For me, pg_database_size gives numbers that match up fairly well with
> > >> what "du" says. I would not expect an exact match, since du probably
> > >> knows about filesystem overhead (such as metadata) whereas
> > >> pg_database_size does not. Something's fishy if it's off by any large
> > >> factor, though. Perhaps you have some tables in a nondefault
> > >> tablespace, where du isn't seeing them?
> >
> > > Nope. Its a pretty much clean database without any fancy stuff.
> >
> > Peculiar. If you want to put some time into it, you could try comparing
> > sizes table-by-table to see if you can isolate where the discrepancy is.
> >
> >
> Perhaps with the contrib adminpack you may easily find where it comes from
> comparing size from pg_table_size and pg_stat_file ?
>

You don't need the adminpack extension to use pg_stat_file. pg_stat_file
is in PostgreSQL core.

--
Guillaume
http://blog.guillaume.lelarge.info
http://www.dalibo.com