private void iterateSelectionHasNulls(
        Aggregation myagg,
        int batchSize,
        boolean[] isNull,
        int[] selected) {

      for (int j=0; j< batchSize; ++j) {
        int i = selected[j];
        if (!isNull[i]) {
          myagg.count += 1;
        }
      }
    }
class for storing the current aggregate value.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/aggregates/VectorUDAFCount.java