private void putDummyOrEmpty(Byte i) {
    // put a empty list or null
    if (noOuterJoin) {
      storage[i] = emptyList;
    } else {
      storage[i] = dummyObjVectors[i];
    }
  }
Decides if the actual row must be an unmatched row.

Unmatched rows are those which are not part of the inner-join.
The current implementation has issues processing filtered rows in FOJ conditions.
Putting them in a separate group also reduces processing done for them.
ql/src/java/org/apache/hadoop/hive/ql/exec/CommonMergeJoinOperator.java