On Fri, 2003-08-22 at 11:17, Shridhar Daithankar wrote:
> On 22 Aug 2003 at 11:03, Jan Wieck wrote:
> > That's why I think it needs one more pg_stat column to count the number
> > of vacuumed tuples. If one does
> >
> > tuples_updated + tuples_deleted - tuples_vacuumed
> >
> > he'll get approximately the number of tuples a regular vacuum might be
> > able to reclaim. If that number is really small, no need for autovacuum
> > to cause any big trouble by scanning the relation.
> >
> > Another way to give autovacuum some hints would be to return some number
> > as commandtuples from vacuum. like the number of tuples actually
> > vacuumed. That together with the new number of reltuples in pg_class
> > will tell autovacuum how frequent a relation really needs scanning.
>
> This kind of information does not really help autovacuum. If we are talking
> about modifying backend stat collection algo., so that vacuum does minimum
> work, is has translate to cheaper vacuum analyze so that autovacuum can fire it
> at will any time. In the best case, another resident process like stat
> collector can keep cleaning the deads.
I believe what Jan is talking about is knowing when to use a normal
vacuum, and when to do a vacuum decent. So his proposal is working
under the assumption that there would be a cheaper vacuum analyze that
can be run most of the time.
