Re: HOT patch, missing things

On 8/14/07, Gregory Stark <stark(at)enterprisedb(dot)com> wrote:
>
> "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
>
> >
> > Doesn't this design completely fail to take index bloat into account?
> > Repairing heap fragmentation does not reduce the need for VACUUM to work
> > on the indexes.
>
> Index bloat is a bit of an open issue already. Because page splits already
> prune any LP_DELETEd pointers any busy index keys will be pruned already.

However any index keys which have not been the subject of an index lookup --
> and that includes keys which are only accessed by bitmap-index-scans --
> won't
> be pruned.
>
> So we don't really know how much bloat is currently in an index. Perhaps
> we
> need a new statistic which gets updated whenever a page split prunes
> LP_DELETEd pointers (or perhaps when LP_DELETE is set?).

I agree here. As a first step, may be can address the heap space usage
statistics and then take up index stats separately. Index bloat would carry
a different weight in triggering autovacuum.

I shall code up a patch which tracks the dead space in the heap and
trigger autovac based on that.

Thanks,
Pavan

--
Pavan Deolasee
EnterpriseDB http://www.enterprisedb.com