@Override
    public Object next() {
      checkForComodification();
      idx++;
      return null;
    }
This can be used for functions with no parameters.
next() function in this impl does not fetch anything from rowContainer, thus saving IO.
It just increments the pointer to maintain iterator contract.
ql/src/java/org/apache/hadoop/hive/ql/exec/PTFPartition.java