1. To get precise result, top n query has to scan a full cuboid (not cube). There are very fast estimates result if 100% correctness is not required.
2. You are correct, that's why we recommend list filtering dimensions before the rest in http://www.slideshare.net/YangLi43/design-cube-in-apache-kylin Cheers On Thu, Apr 9, 2015 at 9:11 PM, 林澍荣 <[email protected]> wrote: > hi, kylin team, > 1. does a topk query scan all the data in the cube table? > 2. does the order of the dimensions in rowkey effect the query speed? for > example, a rowkey consists of A,B,C dimension in order, and will a query > with "WHERE A=a" be finished faster than another with "WHERE C=c"? In my > view, as the hbase table rows are sorting in the lexicographical order, and > the former query will result in a partial scan with a rowkey scale from "a" > to "aa", while the latter one will result in a full scan. But I don't know > whether the hbase coprocessor will do anything to make the latter one > efficient. I'd like to know how Kylin deals with it. > > if I get anything wrong, I will appreciate any correction. > > thanks, Shon >
