Re: strange fsm issues

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.


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