alamb opened a new issue #1425:
URL: https://github.com/apache/arrow-datafusion/issues/1425


   **Background**
   
   @hntd187  fixed https://github.com/apache/arrow-datafusion/issues/1361 via 
https://github.com/apache/arrow-datafusion/pull/1378 but when I was reviewing 
the code, I found several other places that project `RecordBatch`s and 
`Schemas` that may also have the same subtle issues about losing the metadata. 
I am not sure of any bugs related to this yet but I fear they are lurking
   
   The basic idea is to make functions like
   
   ```rust
   fn project_schema(schema: &Schema, projection: &[usize]) -> <Schema> {
   ...
   }
   
   fn project_batch(batch: &RecordBatch, projection: &[usize]) -> 
Result<RecordBatch> {
   ...
   }
   ```
   And replace the duplicated code like
   
   ```rust
           let projected_schema = match &projection {
               Some(columns) => {
                   let fields: Result<Vec<Field>> = columns
                       .iter()
                       .map(|i| {
                           if *i < schema.fields().len() {
                               Ok(schema.field(*i).clone())
                           } else {
                               Err(DataFusionError::Internal(
                                   "Projection index out of range".to_string(),
                               ))
                           }
                       })
                       .collect();
                   Arc::new(Schema::new(fields?))
               }
               None => Arc::clone(&schema),
           };
   ```
   ALl over the datafusion codebase
   
   **Additional context**
   Here is a corresponding arrow ticket to put the logic into arrow-rs: 
https://github.com/apache/arrow-rs/issues/1014


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