[GitHub] [arrow-datafusion] lst-codes commented on pull request #1392: Fix index out of bounds for stats on nested fields

[GitBox <gi...@apache.org>]

lst-codes commented on pull request #1392:
URL: https://github.com/apache/arrow-datafusion/pull/1392#issuecomment-989029092


   > Thanks @andrei-ionescu for taking a stab at this. I don't think we can just flatting all the columns like how it's handled in parquet because the rest of the datafusion code base assumes arrow's hierarchical column structure. As a result, column indexes only map to top level columns. I suspect this approach will not cause runtime crashes because we are only expanding the column vector, but it could lead to incorrect read of column stats in places like
   > 
   > https://github.com/apache/arrow-datafusion/blob/069449f754c92765a2d0dbbf62cd7bac76257892/datafusion/src/physical_optimizer/aggregate_statistics.rs#L181
   
   @houqp 
   
   Do you think column statistics should include something similar to `Field#fields()`, which returns a list of subfields for nested structures? 
   
   https://github.com/apache/arrow-rs/blob/master/arrow/src/datatypes/field.rs#L110-L125


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