This is a bump of KYLIN-976 in case you are not yet aware... KYLIN-976 is a refactoring of how Kylin works with aggregation and aims to allow adding custom aggregation types easily.
Kylin started with basic support of SUM, COUNT, MAX, MIN, AVG (from sum and count), and COUNT_DISTINCT (based on hyperloglog). Later TopN is added in 2.x branch. And the list is growing for sure. Xiaoyu is working on storing raw records as a special type of measure (KYLIN-1122), also Yerui is working on precise count distinct using bitmap (KYLIN-1186). The possibility is unlimited. Implement a domain specific aggregation is now quite easy. E.g. aggregate user events to detect time serials or access patterns. Or draw a sketch of certain user groups. Or pre-calculate clusters of data points. Or histogram... Use your imagination. Whoever interested can peek at MeasureTypeFactory and MeasureType on 2.x branch. The API may still change, but at the same time is stable enough for pilots. The javadoc should get you started. HLLCMeasureType and TopNMeasureType are two good examples. Cheers Yang
