funkybob / django-closure-tree

Closure view based Tree models for Django

Django closure tree model.

Abstract base model for creating a Closure Tree using a recursive Postgres view.

https://schinckel.net/2016/01/27/django-trees-via-closure-view/

Usage

Inherit from the Node model:

from closure_tree.models import Node


class MyNode(Node):
    name = models.CharField(max_length=30)

Create migrations:

$ ./manage.py makemigrations

Add the CreateTreeClosure migration step:

$ ./manage.py makemigrations --empty myapp

from closure_tree.migrations import CreateTreeClosure

class Migration(migrations.Migration):

    dependencies = [
        ('dummy', '0001_initial'),
    ]

    operations = [
        CreateTreeClosure('MyNode'),
    ]

django-closure-tree's Issues

Materialised Path View

It's also possible to have a materialised path view that does the same basic thing as this - but is that too much feature creep?

CREATE OR REPLACE RECURSIVE VIEW {view}(node_id, ancestors) AS

SELECT node_id, ARRAY[]::INTEGER[] AS ancestors
FROM {table} WHERE parent_id IS NULL

UNION ALL

SELECT node_id, ancestors || parent_id
FROM {table}
INNER JOIN {view} ON (parent_id = node_id);

It seems this may be useful - in the case of fetching the list of ancestors, it could then be done without building the other view (and then aggregating that, and remembering to include ordering).

'ancestors' attribute is not showing on Node subclass.