@Override
    public void close() throws IOException {
      if (writer != null) {
        writer.close(false);
      }
      if (deleteEventWriter != null) {
        deleteEventWriter.close(false);
      }
    }
This input format returns its own input split as a value.  This is because our splits
contain information needed to properly construct the writer.  Crazy, huh?
ql/src/java/org/apache/hadoop/hive/ql/txn/compactor/MRCompactor.java