tustvold opened a new issue #1361:
URL: https://github.com/apache/arrow-datafusion/issues/1361


   **Describe the bug**
   
   `ProjectionExec` does not preserve field metadata when generating the 
projected schema. I believe this will also cause it to lose dictionary 
information for the field.
   
   I think fixing this will require extending PhysicalExpr with a `fn 
field(&self, input_schema: &Schema) -> Result<Field>;` or similar to replace 
the [current 
logic](https://github.com/apache/arrow-datafusion/blob/0facd4d483e8c289ee4e3a89487d0cd1ede1a110/datafusion/src/physical_plan/projection.rs#L68)
 that just constructs a new Field
   
   **To Reproduce**
   
   Create a RecordBatch with a schema with field metadata and pass it through 
ProjectionExec.
   
   **Expected behavior**
   
   There is potentially discussion to be had w.r.t schema-level metadata, but I 
would expect field-level metadata to be preserved for the fields that are 
projected


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