[GitHub] [druid] LakshSingla opened a new pull request #12047: Grouping keys incorrectly reduce where they shouldn't

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

LakshSingla opened a new pull request #12047:
URL: https://github.com/apache/druid/pull/12047


   ### Description
   
   In [Grouping#applyProject](https://github.com/apache/druid/blob/6ac4e2dbb8d2e390f0f4a9c0130ce2fb223c297b/sql/src/main/java/org/apache/druid/sql/calcite/rel/Grouping.java#L188), their is an attempt made to reduce the dimensions on which group by is done, if they are not appearing in the final result/`Project`.
   However, this ends up removing all of the literal dimensions which are present in the group by. 
   Consider the following query
   ```
   SELECT dim1, 'dummy' FROM druid.foo GROUP BY dim1, 'dummy'
   ```
   According to our intentions, the 'dummy' shouldn't be removed in the GROUP BY, since it is present in the projection, but it gets removed (Due to the implementation of the `RelOptUtil.InputFinder.bits(project.getChildExps(), null);` not setting bit corresponding to `dummy` to true. It is a `RexLiteral` as opposed to `RexInputRef`.
   
   In a more obscure case like:
   ```
   SELECT 'A', dim1 FROM druid.foo WHERE m1 = 10310313 AND dim1 = 'dummy' GROUP BY dim1
   ```
   The dim1 gets reduced to 'dummy' by Calcite (and is treated as a literal), which gets subsequently removed by the current implementation of the Groupings#applyProject, and it results a row of ('A', 'dummy') when it shouldn't have returned anything. 
   
   This fix changes the visitor which is used to find  the literals in the input expression, and directly compares the DruidExpression of the literal in the input expression, with the dimensions in the group by. 
   
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   <hr>
   
   ##### Key changed/added classes in this PR
    * `Grouping#applyProject`
   <hr>
   
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   This PR has:
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   - [ ] been tested in a test Druid cluster.
   


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