Hi Kylin Developers, I'm confused about when to use derived dimension and how it will affects query performance. So far I've known that derived dimension will not be included in row key and value, then how kylin achieves to implement query grouping by these dimensions? The "Design Cube in Kylin" document says "Derived dimension reduces combination from 2N to 2 at the cost of extra runtime aggregation." I find it hard to understand.
Also, it's not clear to me what is the requirement for using derived dimension. In "Add Dimension" step, there is a tip saying "Using Derived for One-One relationship between columns, like ID and Name". Does it mean derived dimension should be unique key of the lookup table? If that's the case, the applicable scenario seams limited. I'm aware that there's a JIRA https://issues.apache.org/jira/browse/KYLIN-887 <https://issues.apache.org/jira/browse/KYLIN-887> for it, but I can't wait to know the answer :-) Regards, Dayue
