Regardless if star transformation works for multi-column keys and column bitmap indexes, I very much disagree with the comment below to get rid of surrogate keys. That makes zero sense. I won't go as far as to say using multi-column keys and column bitmap indexes is wrong, but I certainly would not design it that way. Personally I use only single column SKs and all of the data molders that I personally know stick to that as well. Basic searching on this topic in the Internet yields the same findings and recommendations. On Thu, Oct 7, 2010 at 3:26 PM, amonte <ax.mount@xxxxxxxxx> wrote: > 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 >> > > -- Regards, Greg Rahn http://structureddata.org