Re: free space map usage

On Tue, 2003-10-14 at 15:43, Jeremy M. Guthrie wrote:
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> On Tuesday 14 October 2003 02:16 pm, Tom Lane wrote:
> > "Jeremy M. Guthrie" <jeremy.guthrie@berbee.com> writes:
> > > Is there any way to determine how much of the free space map is currently
> > > i= n=20
> > > use?(ie. where and what it is tracking?)  I vacuum on a regular basis but
> > > I= =20
> > > never hold in terms of disk space usage.
> >
> > Not in 7.3 AFAIR.  In 7.4 a full-database VACUUM VERBOSE will end with
> > the info you want:
> >
> > regression=# vacuum verbose;
> > ... much cruft ...
> > INFO:  free space map: 11 relations, 144 pages stored; 272 total pages
> > needed DETAIL:  Allocated FSM size: 1000 relations + 20000 pages = 178 kB
> > shared memory. VACUUM
> > regression=#
> >
> > This tells me I'm only using about 1% of the FSM space (272 out of 20000
> > page slots).
> >
> > > I jacked up the free space map=20
> > > pages but this doesn't appear to be working.
> >
> > You know you have to restart the postmaster to make those changes take
> > effect, right?
> Yup.  I still see no effect after restart.
>

Given that you knew of no way to determine how much free space map you
were using, what is your criteria for it to "appear to be working"?  If
it's that space keeps growing, then your probably not vacuuming
frequently enough.

Robert Treat
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