alamb commented on issue #8657:
URL: https://github.com/apache/arrow-rs/issues/8657#issuecomment-3548003691

   I am pretty sure the issue is that [Lists are encoded like this in parquet 
schema](https://github.com/apache/parquet-format/blob/master/LogicalTypes.md#lists):
   ```
   // List<String> (list non-null, elements nullable)
   // required group my_list (LIST) {
   //   repeated group list {
   //     optional binary element (STRING);
   //   }
   ```
   
   The check for nested types in the parquet cache logic is wrong as it nested 
types have mulitple children,
   but lists only have one child (the "list" group) which in turn has one child 
(the "element").
   
   I think it is wrong for MAPs as well, but I haven't verified that yet.
   
   The fix is simple, but I am working on figuring out where best to put the 
tests
   


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