[GitHub] [arrow-datafusion] alamb commented on issue #790: Rework GroupByHash to support grouping by nulls

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alamb commented on issue #790:
URL: https://github.com/apache/arrow-datafusion/issues/790#issuecomment-888533539


   > Before implementing this proposal it is I think be possible with minimal changes to also to include a null part in the hashmap key, so the key would become something like (bool, Vec<u8>) as hashmap key
   
   @Dandandan  I think this is a version of what I was trying to  explain in the "Alternatives" considered section. I think we need an entire validity mask (as only some of the group keys might be null). Also,  we would need to keep validity in the hash map's *values* to produce the correct output , but we could get that "for free" switching to `ScalarValue` ala https://github.com/apache/arrow-datafusion/pull/788
   
   


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