If you set A, B, and C as mandatory dimensions, that means Kylin will save the cuboid result by grouping A, B, C internally. But that not means you could only query by grouping A, B, C. If you only query A, B. The final result will do post-aggregation by grouping the above cuboid. Same as query grouping A. The cost is performance, since more post-aggregation needed. But if you query by grouping D. There would be no result, since you missed the mandatory dimension.
2016-11-17 13:31 GMT+08:00 张晓明（zhangxiaoming）-技术产品中心 <zhangxiaom...@qiyi.com >: > Hi,all > > I have create a cube in My System with Mandatory Dimensions such > as A B C, and the Measure use count distinct filed “u” will HLL , > > When the segment of the cube complete,I query the result with kylin sql > as “select count(distinct u) from table where A=xxx and b=yyy” or “select > count(distinct u) from table where A=xxx ”. The result is correct > > In my opinion, all of the query condition must be set (A=xxx,B=yyyy,C=zzz) > ,the kylin sql can be wrok, > > The question is How the Kylin query the result and the distinct value is > right ? that is unbelievable > -- With Warm regards Yiming Liu (刘一鸣)
