public RelNode getChosenSemiJoin(int factIdx) {
    return chosenSemiJoins[factIdx];
  }
Returns the optimal semijoin for the specified factor; may be the factor
itself if semijoins are not chosen for the factor.

@param factIdx Index corresponding to the desired factor
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveLoptSemiJoinOptimizer.java