By the way found in this url where we can see compount bitmap indexes and star transformation in action http://www.business-intelligence-quotient.com/?p=21 Which states: *This also means that surrogate keys are not a pre-requisite for star transformation to be used in a dimensional model. So another reason to get rid of them (in most situations).* Thank you Alex 2010/10/7 Greg Rahn <greg@xxxxxxxxxxxxxxxxxx> > I dont think your schema design will work for star transformation. I > believe the requirement is: > - primary key on column of dimension table > - bitmap index on SK column on fact table > > In both cases its single column keys. Given you cant have 2 single column > primary keys on your dimension table, it would seem it would not work. > > In good design there is a single column PK and SK on the dimension and fact > table. > > On Thu, Oct 7, 2010 at 12:25 AM, amonte <ax.mount@xxxxxxxxx> wrote: > >> Hi >> >> I am reading 11.1 and 11.2 Data Warehousing Guide and where it explains >> about using star transformation with bitmap index in both release it states: >> >> *A prerequisite of the star transformation is that there be a >> single-column bitmap index on every join column of the fact table. These >> join columns include all foreign key columns.* >> >> Is it saying that bitmap index cannot be composite? >> >> So for example if fact table has FK against dimension such as >> >> fact.c1 ----> dim1.c1 >> fact.c2 ----> dim1.c2 >> >> We cannot create a bitmap index on fact.c1 and fact.c2? But we can create >> two seperate bitmap index each for each fact table column? >> >> >> Alex >> >> > > > -- > Regards, > Greg Rahn > http://structureddata.org >