public static List<ColStatistics> getColStatisticsUpdatingTableAlias(Statistics parentStats) {
    List<ColStatistics> cs = Lists.newArrayList();

    for (ColStatistics parentColStat : parentStats.getColumnStats()) {
      ColStatistics colStat;
      colStat = parentColStat.clone();
      if (colStat != null) {
        cs.add(colStat);
      }
    }

    return cs;
  }
Get column statistics from parent statistics given the
row schema of its child.
@param parentStats
         - parent statistics
@return column statistics
ql/src/java/org/apache/hadoop/hive/ql/stats/StatsUtils.java