@Override
    public String toString() {
      StringBuilder sb = new StringBuilder();
      sb.append(" bytesRead: ").append(bytesRead);
      sb.append(" bytesWritten: ").append(bytesWritten);
      sb.append(" readOps: ").append(readOps);
      sb.append(" largeReadOps: ").append(largeReadOps);
      sb.append(" writeOps: ").append(writeOps);
      return sb.toString();
    }
Convenience class over Hadoop's FileSystem.Statistics.StatisticsData.
Unfortunately, neither the fields, nor the convenience methods (e.g. StatisticsData.add, StatisticsData.negate)
are available here as they are package protected, so we cannot reuse them.
llap-common/src/java/org/apache/hadoop/hive/llap/LlapThreadLocalStatistics.java