@Override
  protected Long minus(Long number1, Long number2) {
    return VectorPTFEvaluatorHelper.minus(number1, number2);
  }
This class evaluates long avg() for a PTF group.

Sum up non-null column values; group result is sum / non-null count.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/ptf/VectorPTFEvaluatorLongAvg.java