alamb commented on PR #20292:
URL: https://github.com/apache/datafusion/pull/20292#issuecomment-4037988529

   > @alamb do you see any way we can have NDV/distinct_count when generating 
test files via that tool?
   > 
   > There has been a lot of activity and interest lately around NDV (including 
myself), it'd be nice to be able to track progress via this new test suite.
   
   @asolimando I think we would need to add support to arrow-rs for writing the 
distinct statistics first
   - https://github.com/apache/arrow-rs/issues/8608 
   
   One challenge we have had so far is that distinct count is often quite 
memory and CPU expensive to calculate (there are less intensive estimates too 
like hyper log log but the actual parquet statistics call for NDV). 
   
   


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