@Override
  public String getName() {
    return getOperatorName();
  }
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