sunchao commented on PR #5558:
URL: 
https://github.com/apache/datafusion-comet/pull/5558#issuecomment-5534196629

   **I’d ask for it in this PR, at medium priority (P2).** The current 
implementation is correct, but the improvement is a small predicate/branch swap 
with reproducible savings and no added abstraction.
   
   Its importance depends on the query:
   
   - **Two arguments or a constant non-null replacement:** unaffected; these 
calls already avoid the guard.
   - **A replacement column containing mixed nulls:** meaningful savings. We 
measured about 29% less expression time for short arrays at 50% null 
replacements.
   - **Large arrays with mostly null replacements:** potentially substantial. 
The current guard copies considerable data that it immediately discards.
   
   The whole-query benefit remains unmeasured. A 97.5% reduction in this 
expression’s time does **not** imply a similar query speedup.
   
   The strongest reason to take it now is the favorable tradeoff: **a tiny 
change removes avoidable work while preserving the existing design and tested 
error behavior.** The evidence supports that small fix; it does not justify a 
larger custom implementation.


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