[Mondrian] Aggregate tables and distinct-count

Luc Boudreau lucboudreau at gmail.com
Mon Jan 14 12:41:18 EST 2013


Depends on the structure of your dimension table. If you create a 1:N
relation by using non-collapsed levels, then yeah, you'll have wrong
results returning.

Luc


On Mon, Jan 14, 2013 at 12:17 PM, Pedro Alves <pmgalves at gmail.com> wrote:

> The agg has one single (non-collapsed) level, and this is a star schema.
> Could I get into troubles?
>
>
>
> On 01/14/2013 05:14 PM, Luc Boudreau wrote:
> > Be careful with the non-collapsed dimensions. This feature needs the
> > tables to be in a snowflake form. If the dimension table is a single
> > table and you join on the non-last level, you will get a cartesian
> product.
> >
> > Luc
> >
> > On Mon, Jan 14, 2013 at 12:04 PM, Pedro Alves <pmgalves at gmail.com
> > <mailto:pmgalves at gmail.com>> wrote:
> >
> >
> >
> >     IT IS WORKING!
> >
> >
> >     However, I had to skip the first level of a hierarchy, marking the
> >     second level as collapsed= false.. something I've never used before
> and
> >     seems to be exactly for this :p
> >
> >
> >
> >     -pedro
> >
> >
> >
> >
> >     On 01/14/2013 05:01 PM, Julian Hyde wrote:
> >      > yes, it should be used.
> >      >
> >      > furthermore, mondrian knows that it is safe to roll up any
> >     attributes that are functionally dependent on the measure column.
> >     (e.g. if you have computed count(distinct customer_id), and you have
> >     in the agg table the distinct count for male and female customers in
> >     each state, you can compute the number of distinct customers in each
> >     state by adding the distinct males and females.)
> >      >
> >      > Julian
> >      >
> >      >
> >      > On Jan 14, 2013, at 8:52 AM, Pedro Alves <pmgalves at gmail.com
> >     <mailto:pmgalves at gmail.com>> wrote:
> >      >
> >      >>
> >      >>
> >      >> I know we can't aggregate distinct-count measures like we do
> >     with the
> >      >> others.
> >      >>
> >      >> But if a query matches a specific aggregation table's bitkey,
> >      >> couldn't/shuoldn't it be used?
> >      >>
> >      >>
> >      >>
> >      >> -pedro
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