chenkovsky commented on PR #14057:
URL: https://github.com/apache/datafusion/pull/14057#issuecomment-2644409227

   > Do you know the rationale for spark that why it doesn't consider projected 
columns as normal column?
   
   If my memory is correct, it's also designed for dataframe api user. for 
`withColumn` clause, it's a project.
   dataframe users often chain withColumn operators.
   
   ```python
   df.withColumn(...).withColumn(...)
   ```
   
   If project cannot propagate metadata/system columns, it's very hard to use 
this chain.
   
   I cannot tell are there any other differences between spark standard and 
#14362 's standard because most sqls will have at least one project.


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