storing the tree as an MPTT/NestedSet would massively simplify this, without any subquery shenanigans.

https://en.m.wikipedia.org/wiki/Nested_set_model

https://imrannazar.com/articles/modified-preorder-tree-trave...

Well the read query has simpler syntax with MPTT but implementing the whole structure is more complicated and any re-organization like moving a folder around requires rewriting a lot of rows. Although it doesn’t apply to the Firefox use-case, I’ve never understood how this technique can be applied to anything but the most trivially sized, roughly immutable trees. What do you do in a production system when two people move two different node in the tree? It seems to need all kinds of complicated locks.

There are at least five ways to store a tree in PostgreSQL, for example: adjacency list, nested sets like MPTT Modified Preorder Tree Traversal, nested intervals, Materialized Paths, ltree, JSON

E.g. django-mptt : https://github.com/django-mptt/django-mptt/blob/main/mptt/mo... :

  indexed_attrs = (mptt_meta.tree_id_attr,)
  field_names = (
    mptt_meta.left_attr,
    mptt_meta.right_attr,
    mptt_meta.tree_id_attr,
    mptt_meta.level_attr, )

> The nested interval model stores the position of the nodes as rational numbers expressed as quotients (n/d).