mptt

I have a table in my database where I store a tree structure using the hybrid Nested Set (MPTT) model (the one which has lft and rght values) and the Adjacency List model (storing parent_id on each node). my_table (id, parent_id, lft, rght, alias) This question doesn't relate to any of the MPTT aspects of the tree but I thought I'd leave it in in case anyone had a good idea about how to leverage that. I want to convert a path of aliases to a specific node. For example: "users.admins.nickf" would find the node with alias "nickf" which is a child of one with alias "admins" which is a child of

Does anybody have an efficient algorithm to retrieve all ancestors of an mptt queryset? The best I could think of so far is something like this: def qs_ancestors(queryset): if isinstance(queryset, EmptyQuerySet): return queryset queryset_aggs = queryset.values_list('tree_id', 'level').annotate(max_lft=Max('lft'), min_rght=Min('rght')) new_queryset = queryset.none() for tree_id, level, max_lft, min_rght in queryset_aggs: ancestors = MyModel.objects.filter( tree_id=tree_id, level__lt=level, lft__lte=max_lft, rght__gte=min_rght, ) new_queryset = ancestors | new_queryset return new_queryset There

I'm using nested sets (aka modified preorder tree traversal) to store a list of groups, and I'm trying to find a quick way to generate breadcrumbs (as a string, not a table) for ALL of the groups at once. My data is also stored using the adjacency list model (there are triggers to keep the two in sync). So for example: ID Name ParentId Left Right 0 Node A 0 1 12 1 Node B 0 2 5 2 Node C 1 3 4 3 Node D 0 6 11 4 Node E 3 7 8 5 Node F 4 9 9 Which represents the tree: Node A Node B Node C Node D Node E Node F I would like to be able to have a user-defined function that returns a table: ID

I'm trying to make a model for categorizing some objects. I already tried using django-mptt to easily retrieve related categories, and now I'm searching different solutions to find the best one. I can't find out though what are main differences between Materialized Path, Adjacency List and Nested Set. Wikipedia didn't give me a short answer, all I know is mptt is probably Nested Set... Can anyone explain it to me in few words ? It's easier to explain with examples than with a few words. Consider the sample tree, storing names: William Jones Blake Adams Tyler Joseph Miller Flint Materialized

For a while now I've been wrestling with how best to handle hierarchies in SQL. Frustrated by the limitations of adjacency lists and the complexity of MPTT/nested sets, I began thinking about simply storing key paths instead, as a simple node_key/node_key/... string. I decided to compile the pros and cons of the three techniques: Number of calls required to create/delete/move a node: Adjacency = 1 MPTT = 3 Path = 1 (Replace old node path with new node path across all nodes that contain that path) Number of calls required to get a tree: Adjacency = [number of sub-levels] MPTT = 1 Path = 1