I see. How would this be different than a normal group by though when running queries in Kylin sql? What is the difference between specifying this hierarchy and just a normal dimension for each?
On Fri, Sep 18, 2015 at 3:22 AM, Li Yang <[email protected]> wrote: > Yes, the "roll-up" understanding is correct. > > Defining one hierarchy made up of the three dimensions is good enough. It > covers all 3 roll-ups. The order of dimensions matters because hierarchy > basically describes a "contains" relationship, like CONTINENT => COUNTRY => > CITY. A wrong order will impact performance at both build time and query > time. > > On Thu, Sep 17, 2015 at 11:27 PM, Patrick McAnneny < > [email protected]> wrote: > > > The way I understand the hierarchy feature (lets say with three columns > > specified) is the following: "create a roll-up aggregate grouping by this > > column, then that column, then that column" Is this correct > understanding? > > > > If I would want to query potentially based on any combination of those > > three roll-ups, would it be best to create three separate hierarchy > > dimensions or the combination of each? Would order even matter here? > Order > > does not usually matter in 'group by' statements > > >
