Calcite has the rule that does the work. But you can't remove the group by clause if the constant is the only group key. The semantic is different without group key. Try it on empty relation, you will see the difference.
Thanks~ Haisheng Yuan------------------------------------------------------------------ 发件人：Krzysztof Zarzycki<k.zarzy...@gmail.com> 日 期：2019年06月26日 21:52:41 收件人：<dev@calcite.apache.org> 主 题：Modify Calcite Planner in Hive to remove GROUP BY <constant> Hello, While the question I have might look like regards to Hive, I believe is more about Calcite. I need to add a Calcite plan rule to Hive, that removes "Group by" clause when it groups by some constant value (GROUP BY TRUE more precisely). As far as I believe, the query semantically is the same. Could anyone on this mailing list help me how to do it properly? While I'm an experienced java engineer, I have no clue how to achieve this. I was trying to modify hive code to do this myself, but unfortunately I got only NullPointerExceptions. More context below: I want to use JdbcStorageHandler in Hive, that connects to Apache Kylin and forward queries there. Then I put Tableau on top of Hive. Unfortunately, the queries produced by Tableau to Hive and then reproduced by Calcite Planner to Kylin, cannot be handled by Kylin (which BTW uses Calcite as well). I disabled some of the hive optimizations which fixed some of my queries. But I'm stuck on one I cannot disable. Tableau generates a query with "GROUP BY 1.000000...01" , that is translated to "GROUP BY TRUE", by Hive/Calcite. But neither of those can be handled by Kylin. I got an idea that I will remove GROUP BY completely, because in my understanding it's unecessary. I will be very grateful for your help, Kind Regards, Krzysztof
