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

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