public boolean isNullGenerating(int factIdx) {
    return joinTypes.get(factIdx).isOuterJoin();
  }
Returns whether the factor corresponds to a null-generating factor
in a left or right outer join.

@param factIdx Factor for which information will be returned
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveLoptMultiJoin.java