cache parent_id or root_id

[tilo]

It would be nice to have Klass.is_parent as a scope

e.g. in a User model you often want to find all managers quickly

EDITED by kbrock:

This will allow us to fetch leafs and non-leaf nodes (discussion moved to #422)
It also cuts down a lot on processing if the parent_id is cached.
Caching in the database would be the best

[tilo]

@stefankroes bump..

[kbrock]

@tilo There are a few posts that talk about "leaves" that I think are similar to your request.

since the fact that this is a parent is not stored in the record itself, but the presence of other records, means this would be a query with an exists clause.

Have you come up with a query that meets your needs?

[KevinColemanInc]

I can jump in here as I worked with tilo on this problem.

We ended up doing this adding a separate parent id column. For our purposes, it made simple queries for:

1. Finding everyone that is a parent
2. Joining against the parent

  before_save :sync_parent_id_from_ancestry, if: :ancestry_changed?

  def sync_read_only_parent_id_from_ancestry
    write_attribute(:read_only_parent_id, self.parent_id)
  end

[kbrock]

I think the solution is to revamp the nodes like suggested in #422 - we need to start using sql instead of the darned to_node junk

[kbrock]

@KevinColemanInc This is very old...

I'm leaving the asking for leafs / parents over in #422

I'm taking liberty for the definition of this feature request as caching parent_id
there is a lot of stuff you could get from there