public LogicalJoin getJoinRemovalSemiJoin(int dimIdx) {
    return joinRemovalSemiJoins[dimIdx];
  }
Returns the semi-join that allows the join of a dimension table to be
removed.

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