If a row key column wasn¹t appeared in any aggregation group, and it is not ³mandatory², Kylin will put it into a group named as ³tail².
Moving column to ³tail² will reduce the generated cuboid numbers, so to reduce the calculation as well as storage; This is a cube optimization method in Kylin, for advanced user. On 4/14/15, 4:31 PM, "[email protected]" <[email protected]> wrote: >Hi, all > >*RowKeyDesc* there is a tailMask and its value is assigned by > this.tailMask = fullMask ^ mandatoryColumnMask ^ aggrGroupFullMask >AFAIK, fullMask would be all 1 byte and mandatoryColumnMask would be byte >with only mandatory column desc got assgining value 1. > >aggrGroupFullMask goes to the value that only present on each aggregation >group would be assigned as 1. > >But this.tailMask made me a little confused and CANNOT quite catch the >real meaning. > >Hope for some interesting explaination : ) > >Best, >Sun. > > > >[email protected]
