Re: bitmap index and star transformation must be single colum?

Hi Greg

So that means that in Oracle if we want star transformation we must use
surrogate keys for all dimensions and fact tables FK?


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
>

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