andygrove opened a new issue, #4835:
URL: https://github.com/apache/datafusion-comet/issues/4835

   `first_value` / `last_value` over a `RANGE` frame that uses a literal 
`PRECEDING`/`FOLLOWING` offset fall back to Spark today.
   
   See `spark/src/main/scala/org/apache/spark/sql/comet/CometWindowExec.scala` 
(around lines 404-420), which records "FIRST_VALUE with RANGE frame and literal 
offset is not supported" / "LAST_VALUE with RANGE frame and literal offset is 
not supported".
   
   Comet's stateless native RANGE frame cannot reproduce Spark's monotonic 
lower-bound iterator semantics under non-ANSI overflow, so it falls back rather 
than risk an incorrect result.
   
   Documented as a current limitation in the window function compatibility 
guide.


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