private static void propagateNullsCombine(boolean selectedInUse, int n, int[] sel,
      ColumnVector inV1, ColumnVector inV2, BytesColumnVector outV) {
    if (selectedInUse) {
      for(int j = 0; j != n; j++) {
        int i = sel[j];
        outV.isNull[i] = inV1.isNull[i] || inV2.isNull[i];
      }
    } else {
      for(int i = 0; i != n; i++) {
        outV.isNull[i] = inV1.isNull[i] || inV2.isNull[i];
      }
    }
  }
Propagate the logic OR of null vectors from two inputs to output.

@param selectedInUse true/false flag to tell if sel[] is in use
@param n number of qualifying rows
@param sel selected value position array
@param inV1 input vector 1
@param inV2 input vector 2
@param outV output vector
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/StringGroupConcatColCol.java