private boolean isLess(Object in, Object last) {
      if (in == null) {
        return false;
      }
      if (last == null) {
        return true;
      }
      return ObjectInspectorUtils.compare(in, inputOI(), last, outputOI()) < 0;
    }
class for storing the current max value
ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDAFMin.java