Kimahriman opened a new issue, #1121:
URL: https://github.com/apache/datafusion-comet/issues/1121

   ### Describe the bug
   
   Because Delta scans work by using a subclass of `ParquetFileFormat` within a 
normal Hadoop relation, Comet will see this and simply replace it with a 
`CometParquetFileFormat`, losing all the Delta-specific things in it's own 
subclass, such as deletion vector support and column mapping
   
   ### Steps to reproduce
   
   Don't have exact steps right now, noticed this randomly while testing things 
out and kind of expected this to be a problem.
   
   ### Expected behavior
   
   If doing a Delta scan, it should not be eligible to be converted to a 
CometScan. The check for `ParquetFileFormat` probably needs to be an exact 
class comparison that doesn't include subclasses.
   
   Longer term it would be interesting if it is possible to delegate the 
necessary behavior to custom file formats, but all the work trying to push down 
the Parquet scans to datafusion might make that impossible unless a different 
approach like using delta-rs directly is used such as in #174 
   
   ### Additional context
   
   _No response_


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