Can you define what "nested sets" means more specifically? Postgres supports hierarchical/nested structures using the "ltree" column type. There is nothing st

Can you define what "nested sets" means more specifically? Postgres supports hierarchical/nested structures using the "ltree" column type. There is nothing stopping you from defining a primary key of (eg) "set1.set10.set100". There is also support for recursive views/etc to operate on these kinds of sets. Again, if you have some kind of "sparse" column, it can make sense to put that into a JSONB column. This is effectively the same thing as attaching an unstructured document to a record for this use-case.