Merging parquet files

merge.rs

//
// WARNING: Not a complete executable program, this is for demonstration purposes
//

fn main() -> Result<(), CustomError> {
    /// .. get input and output from the user
    for input in inputs {
        dump_contents(input, output)?;
    }
    
    Ok(())
}

pub fn dump_contents(input: &str, output: &str) -> Result<(), CustomError> {
    // .. open_file is a function that returns a fs::File
    let input_file = open_file(input)?;
    let output_file = File::create(output)?;

    let reader = SerializedFileReader::new(input_file).unwrap();
    let mut arrow_reader = ParquetFileArrowReader::new(Arc::new(reader));
    let mut arrow_batch_reader = arrow_reader.get_record_reader(1024).unwrap();
    let first_batch = arrow_batch_reader.next().unwrap().unwrap();
    let arrow_schema = first_batch.schema();
    debug!("{:#?}", &arrow_schema);

    let mut writer =
        ArrowWriter::try_new(output_file.try_clone().unwrap(), arrow_schema, None).unwrap();
    writer.write(&first_batch).unwrap();

    while let Some(batch) = arrow_batch_reader.next() {
        let record_batch = batch.unwrap();
        writer.write(&record_batch).unwrap();
    }
    writer.close().unwrap();
    
    // how to update FileMetaData at the end?

    Ok(())
}