[GitHub] [druid] FrankChen021 edited a comment on issue #10530: Allow zero period for TIMESTAMPADD to help make Tableau operable

[GitBox <gi...@apache.org>]

FrankChen021 edited a comment on issue #10530:
URL: https://github.com/apache/druid/issues/10530#issuecomment-716472662


   I made some investigation about this problem, and I think it should be a bug. 
   
   It's interesting that `TIMESTAMPADD` works fine with `DAY`, `MINUTE` when the 2nd parameter is zero, while `MONTH`, `YEAR` fail.
   
   Druid's internal implementation converts calling of `TIMESTAMPADD` to `TIME_SHIFT`, and its parameters are also converted to a type of `Period` which is accepted by the latter function. And the code dealing with `Period`, which checks period should not be zero mainly for query granularity,  are shared across the whole project. 
   
   While for the cases of `DAY` or `MINUTE`, Druid converts it to an integer value in milliseconds, which does not involve a `Period` object. This is also why the existing [UT test case](https://github.com/apache/druid/blob/f3a2903218573f5d336b082b1c9b8a60a19e8c54/sql/src/test/java/org/apache/druid/sql/calcite/CalciteQueryTest.java#L11393) don't help to expose this bug.  
   
   @gianm what do you think ?


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