This is a problem that ActiveRecord-style ORM's have failed to solve. One possible solution is writing queries like in the article that transform normalized data from the DB into a JSON structure. Another possibility is to design an ORM that is actually capable of taking a set of relations and dynamically building queries with joins, then transforming the returned rows into tree like structures.

This is a very interesting area for exploring a new kind of ORM. I find the whole "CRUD monkey" shtick preached by DHH et al quite lacking for expressing the kind of hierarchical data structures developers need.