"Greg Stark" <gsstark@mit.edu> wrote
>
> If the whole database is in RAM I wouldn't expect clustering to have any
> effect. Either you're doing a lot of merge joins or a few other cases
> where
> clustering might be helping you, or the cluster is helping you keep more
> of
> the database in ram avoiding the occasional disk i/o.
>
Hi Greg,
At first I think the same - notice that Tom has submitted a patch to scan a
whole page in one run, so if Harry tests against the cvs tip, he could see
the real benefits. For example, a index scan may touch 5000 tuples, which
involves 5000 pairs of lock/unlock buffer, no matter how the tuples are
distributed. After the patch, if the tuples belong to a few pages, then a
significant number of lock/unlock are avoided.
Regards,
Qingqing
