"Greg Stark" <gsstark@xxxxxxx> 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
