I was preparing a email with related doubts:
Some times we have derived dimensions with relation 1:1, examples:
WeekDayID & WeekDayTxt
MonthID & WeekTxt
SOL1: Derived. ID as Host and Txt Extended
PB: You can't filter / Group by Txt
SOL2: Joint. Define tuples of ID & TXT
Some PB/limitation? (I need test this option)
2016-12-01 0:35 GMT+01:00 Billy(Yiming) Liu <liuyiming....@gmail.com>:
> Thanks, Alberto. The explanation is accurate. EXTENDED_COLUMN is only used
> for representation, but not filtering or grouping which is done by
> HOST_COLUMN. So EXTENDED_COLUMN is not a dimension, it works like a
> key/value map against the HOST_COLUMN.
> If the value in EXTENDED_COLUMN is not long, you could just define two
> dimensions with joint dimension setting, it has almost the same performance
> impact with EXTENDED_COLUMN which reduces one dimension, but better
> 2016-11-30 19:00 GMT+08:00 Alberto Ramón <a.ramonporto...@gmail.com>:
>> This will help you
>> The idea is always, How I can reduce the number of Dimension ?
>> If you reduce Dim, the time / resources to build the cube and final size
>> it decrease --> Its good
>> An example can be DIM_Persons: Id_Person , Name, Surname, Address, .....
>> Id_Person can be HostColumn
>> and other columns can be calculated from ID --> are Extended Column
>> 2016-11-30 11:35 GMT+01:00 仇同心 <qiutong...@jd.com>:
>> > Hi ,all
>> > I don’t understand the usage scenarios of EXTENDED_COLUMN,although I
>> > this article “https://issues.apache.org/jira/browse/KYLIN-1313”.
>> > What,s the means about parameters of “Host Column” and “Extended
>> > Why use this expression,and what aspects of optimization that this
>> > expression solved?
>> > Can be combined with a SQL statement to explain?
>> > Thanks~
> With Warm regards
> Yiming Liu (刘一鸣)