Rich-T-kid commented on PR #23128:
URL: https://github.com/apache/datafusion/pull/23128#issuecomment-4937006410

   > We could potentially have an optimized dictionary group values that 
somehow wraps another group values and does the dictionary translation 🤔
   
   This is pretty much what https://github.com/apache/datafusion/pull/23187 
does, 
[benchmarks](https://github.com/apache/datafusion/pull/23187#issuecomment-4932432620)
 show good results
   
   > The thing with Dictionaries is that the dictionary indices for hte same 
logical value can vary from batch to batch, so we can't just do the grouping 
based on the dictionary indices
   
   I think theres room to optimize for the low cardinality case similar to what 
#21765 benchmarks showcased. Ive tried a couple approaches but the results have 
not been worth the extra complexity.
   


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