It allows for recursion in the query (fetching a tree of a category structure for instance where it's just a id,parent_id,priority tuple) Handling that efficie

It allows for recursion in the query (fetching a tree of a category structure for instance where it's just a id,parent_id,priority tuple) Handling that efficiently without conditioning the data first using something like nested set or materialized paths is going to be a challenge when the depth is unknown.