eye-gu commented on issue #13811: URL: https://github.com/apache/skywalking/issues/13811#issuecomment-4237481599
> > For testing the distributed TopN query, my entry point was banyand/dquery/topn.go. However, at this entry point, there was no pushdown. > > Aggregation is carried out solely on the liaison node. Each data node sends back its pre-aggregation list, and the liaison node completes the final aggregation. This aggregation process happens during the write phase on each data node, not during querying. That's the reason why there is no push-down. Based on my distribute integration testing, the TopN aggregation during the write phase does not perform SUM/COUNT or other aggregations — it stores the original values. Assuming a data node has the following data: entity1=10 entity1=20 entity2=15 Query TopN=2, SUM: the data node applies top-2 truncation and returns entity1=20, entity2=15. entity1=10 is discarded. Liaison's PostProcessor then performs SUM: entity1: SUM(20)=20, entity2: SUM(15)=15. The correct result should be: entity1: SUM(10+20)=30, entity2: SUM(15)=15. Is my understanding correct? Or am I missing something?Thanks again for your patience! -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
