Yes I agree with what you say, sometimes it's just inconvenient to manipulate a query planner using a high-level language instead of using a more direct approac

Yes I agree with what you say, sometimes it's just inconvenient to manipulate a query planner using a high-level language instead of using a more direct approach. Also, while many databases provide a way to work with underlying representations of their data, it is still quite difficult or impossible to build something entirely new (I.e. a new application) with them.