I have a question that is EXTENDED_COLUMN the same as DERIVED_COLUMN?
On 1 Dec 2016, 07:35 +0800, Billy(Yiming) Liu <[email protected]>, wrote: > 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 <[email protected]>: > > > 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 <[email protected]>: > > > > > 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)
