private void iterate(PercentileAgg percAgg, Object percentiles, Object oderByColumnValue) {
      if (percAgg.percentiles == null) {
        percAgg.percentiles = converter.convertPercentileParameter(percentiles);
      }

      if (oderByColumnValue == null) {
        return;
      }

      T input = getInput(oderByColumnValue, inputOI);

      if (input != null) {
        increment(percAgg, wrapInput(input), 1);
      }
    }
A state class to store intermediate aggregation results.
ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDAFPercentileCont.java