@Override
    public RelOptCost computeSelfCost(RelOptPlanner planner, RelMetadataQuery mq) {
      return planner.getCostFactory().makeInfiniteCost();
    }
Rule that replaces Box operators by the plan they hold.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/views/HiveMaterializedViewBoxing.java