title: Parquet: difference between metadata and common_metadata
body: <p>When writing a metadata file, the ThriftParquetWriter actually generates two files: <strong>_metadata</strong> and <strong>_common_metadata</strong></p>
  
  <p><a href="https://github.com/apache/parquet-mr/blob/master/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileWriter.java" rel="nofollow noreferrer">https://github.com/apache/parquet-mr/blob/master/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileWriter.java</a></p>
  
  <p>Whats the difference between this two files? They have a different file size so there must be a difference</p>
  
  <p>Thanks</p>