Hello
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
> understanding.
>
> 2016-11-30 19:00 GMT+08:00 Alberto Ramón <a.ramonporto...@gmail.com>:
>
>> This will help you
>> http://kylin.apache.org/docs/howto/howto_optimize_cubes.html
>>
>> 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
>> of
>> 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
>> saw
>> > this article “https://issues.apache.org/jira/browse/KYLIN-1313”.
>> > What,s the means about parameters of “Host Column” and “Extended
>> Column”?
>> > 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)
>

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