@Override
  public ResourceStatistics getStatistics(String location, Job job) throws IOException {
    try {
      if (dbName == null || tableName == null) {
        throw new IOException("DB or table name unset. setLocation() must be invoked on this " +
                "loader to set them");
      }
      ResourceStatistics stats = new ResourceStatistics();
      long inputSize = -1;

      LinkedList<InputJobInfo> inputJobInfos = HCatUtil.getInputJobInfosFromConf(
              job.getConfiguration());

      for (InputJobInfo inputJobInfo : inputJobInfos) {
        if (dbName.equals(inputJobInfo.getDatabaseName()) && tableName.equals(inputJobInfo.getTableName())){
          inputSize = getSizeInBytes(inputJobInfo);
          break;
        }
      }

      if (inputSize == -1) {
        throw new IOException("Could not calculate input size for database: " + dbName + ", " +
                "table: " + tableName + ". Requested location:" + location);
      }
      stats.setSizeInBytes(inputSize);
      return stats;
    } catch (Exception e) {
      throw new IOException(e);
    }
  }
Get statistics about the data to be loaded. Only input data size is implemented at this time.
hcatalog/hcatalog-pig-adapter/src/main/java/org/apache/hive/hcatalog/pig/HCatLoader.java