Nice Liu We have some cases like DayWeekTXT , DayWeekID MonthTXT, MonthID
small proposal: Can would be interesting create Derived with 1:1 relation, with support for filters and Group by 2016-12-01 11:55 GMT+01:00 Billy(Yiming) Liu <liuyiming....@gmail.com>: > The cost of joint dimension compared with extended column is you have more > columns in the HBase rowkey. It may harm the query performance. But most > time, joint dimension is still recommended, since the normal dimension > column supports much more functions than extended column, such as count(*). > > 2016-12-01 17:07 GMT+08:00 Alberto Ramón <a.ramonporto...@gmail.com>: > >> 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) >>> >> >> > > > -- > With Warm regards > > Yiming Liu (刘一鸣) >
