Rachelint commented on issue #11680:
URL: https://github.com/apache/datafusion/issues/11680#issuecomment-5021536629

   I also tried this in #23446 before.
   And for clickbench, it seems that only can get improvement in cases with 
expansive hash calculation.
   I think the reason is that:
   - Creating and operating the hash column may be not trivial as we think
   - And also hash calculation for `primitive`s may be also not expansive as we 
think
   
   About how to define `cases with expansive hash calculation`, I think maybe 
we can start from the static and simple rules:
   - reuse when `byte/byte view` or `other more complex columns` appear in 
`group by`
   - reuse when we group by a large amount of columns even all of them are 
`primitive`
   - not reuse in other cases


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