mbutrovich commented on PR #21484:
URL: https://github.com/apache/datafusion/pull/21484#issuecomment-4215134237

   Thanks for the feedback @Dandandan!
   
   > * Conversion to row format for multiple columns (like SPM, topk, etc.) . 
DynComparator is faster but still does dynamic dispatch and for a larger number 
of columns does a bigger number of comparisions.
   
   I'm not sure how common multi-column joins are in practice or how many 
columns we'd need to be comparing to hit the break-even point for the cost of 
conversion for the `RowConverter`. But it's definitely something to keep in 
mind.
   
   > * specializing for single-column case
   
   I suspect the branch predictor will figure this out pretty fast since it 
doesn't change, and the dominant cost is the virtual call through `Box<dyn 
Fn>`. I can try that out, but don't anticipate much of a change.


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