public static void updateStats(Statistics stats, long newNumRows,
      boolean useColStats, Operator<? extends OperatorDesc> op) {
    updateStats(stats, newNumRows, useColStats, op, Collections.EMPTY_SET);
  }
Update the basic statistics of the statistics object based on the row number
@param stats
         - statistics to be updated
@param newNumRows
         - new number of rows
@param useColStats
         - use column statistics to compute data size
ql/src/java/org/apache/hadoop/hive/ql/stats/StatsUtils.java