Currently, our Group By clause follows Hive https://cwiki.apache.org/confluence/display/Hive/Enhanced+Aggregation,+Cube,+Grouping+and+Rollup :
However, this does not match ANSI SQL compliance. The proposal is to update our parser and analyzer for ANSI compliance.
It is nice to support ANSI SQL syntax at the same time.
Note, we only need to support one-level grouping set in this stage. That means, nested grouping set is not supported.
Note, we should not break the existing syntax. The parser changes should be like