Thanks Billy If Kylin save the result separate By A B C,The Times Can be understand, But “count distinct ” is merge the same “u” ,Can’t do ++ Operation “”
From: Billy(Yiming) Liu [mailto:[email protected]] Sent: Thursday, November 17, 2016 2:05 PM To: user <[email protected]> Cc: [email protected] Subject: Re: some confuse about Mandatory Dimensions 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 <[email protected]<mailto:[email protected]>>: 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)
