presto-main/src/main/java/io/prestosql/cost/CostComparator.java/CostComparator/forSession
class CostComparator:    public Ordering<PlanCostEstimate> forSession(Session session)
    {
        requireNonNull(session, "session is null");
        return Ordering.from((left, right) -> this.compare(session, left, right));
    }