Question on how group by aggregations are implemented in Pinot. From what I understand, groupKeys are generated from group by columns’s dictionary ids. How does this work for intersegment and inter server aggregations?

The dictionary id based grouping happens at segment level. Since column dictionary ids are segment specific, it cannot be used for server/broker level grouping. There we have to default to using actual values. May I ask what's your issue? Is it just for understanding of the system, or are you facing an issue that needs to be addressed?

Mostly just understanding the system.