public static void setNullDataEntriesLong(
      LongColumnVector v, boolean selectedInUse, int[] sel, int n) {
    if (v.noNulls) {
      return;
    } else if (v.isRepeating && v.isNull[0]) {
      v.vector[0] = LongColumnVector.NULL_VALUE;
    } else if (selectedInUse) {
      for (int j = 0; j != n; j++) {
        int i = sel[j];
        if(v.isNull[i]) {
          v.vector[i] = LongColumnVector.NULL_VALUE;
        }
      }
    } else {
      for (int i = 0; i != n; i++) {
        if(v.isNull[i]) {
          v.vector[i] = LongColumnVector.NULL_VALUE;
        }
      }
    }
  }
Set the data value for all NULL entries to the designated NULL_VALUE.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/NullUtil.java