On Tue, Jun 27, 2006 at 08:02:33PM -0700, Jeff Frost wrote:
> On Tue, 27 Jun 2006, Jim Nasby wrote:
> >>What the heck? Why would it have shrunk down so much? The vacuum full
> >>isn't scheduled until tonight. :-/
> >Take a look at the source for autovacuum... I'm guessing you're right and
> >that it doesn't make any special considerations for toast tables, which it
> >probably should (since AFAIK you have to first vacuum the base table, then
> >commit, then vacuum the toast table).
> >BTW, tracking pg_class.relpages or actual file size over time would
> >probably be helpful.
> Actually, it says this:
> * Scan pg_class and determine which tables to vacuum.
> * The stats subsystem collects stats for toast tables independently of
> * the stats for their parent tables. We need to check those stats since
> * in cases with short, wide tables there might be proportionally much
> * more activity in the toast table than in its parent.
> * Since we can only issue VACUUM against the parent table, we need to
> * transpose a decision to vacuum a toast table into a decision to vacuum
> * its parent. There's no point in considering ANALYZE on a toast table,
> * either. To support this, we keep a list of OIDs of toast tables that
> * need vacuuming alongside the list of regular tables. Regular tables
> * will be entered into the table list even if they appear not to need
> * vacuuming; we go back and re-mark them after finding all the vacuumable
> * toast tables.
> So I guess it does take toast tables into account.
Only if it issues 2 vacuums on the base tables...
Jim C. Nasby, Sr. Engineering Consultant jnasby(at)pervasive(dot)com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
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