Thanks Alberto for the update. Actually I am investigating the calculations in R10 and my plan was to later cover R11 as well. Since still most of the systems are on R10 and in future also (atleast 2-3 years), I am very interested. Having said that, your references and update will be very helpful. I just downloaded the stuff and reading :-) On Thu, Apr 9, 2009 at 3:44 AM, Alberto Dell'Era <alberto.dellera@xxxxxxxxx>wrote: > On Mon, Apr 6, 2009 at 17:20, Neeraj Bhatia <neeraj.dba@xxxxxxxxx> wrote: > > Basically I am interested to know how density is calculated in case of > > height-based histograms. Also, how CBO calculate selectivity. > > I wouldn't investigate too much the density in 10.x since the formula > has changed (to a very intuitive one) in 11gR1: > > http://www.adellera.it/investigations/11g_newdensity/index.html > > so, the 10.x formula has been "deprecated" by the kernel developers. > > I did find a statistical justification for the 10.x computation, but > I have never "published" it for the above reasons, it is no longer > important. > > hth > alberto >