Utilities for implementing Modified Preorder Tree Traversal with your Django Models and working with trees of Model instances.
Project home: http://github.com/django-mptt/django-mptt/
Discussion group: http://groups.google.com/group/django-mptt-dev
What is Modified Preorder Tree Traversal?
MPTT is a technique for storing hierarchical data in a database. The aim is to make retrieval operations very efficient.
The trade-off for this efficiency is that performing inserts and moving items around the tree is more involved, as there's some extra work required to keep the tree structure in a good state at all times.
Here are a few articles about MPTT to whet your appetite and provide details about how the technique itself works:
* `Trees in SQL`_ * `Storing Hierarchical Data in a Database`_ * `Managing Hierarchical Data in MySQL`_
Trees in SQL: http://www.intelligententerprise.com/001020/celko.jhtml
Storing Hierarchical Data in a Database: http://www.sitepoint.com/print/hierarchical-data-database
Managing Hierarchical Data in MySQL: http://dev.mysql.com/tech-resources/articles/hierarchical-data.html
django-mptt is a reusable Django app which aims to make it easy for you
to use MPTT with your own Django models.
It takes care of the details of managing a database table as a tree structure and provides tools for working with trees of model instances.
Simple registration of models - fields required for tree structure will be added automatically.
The tree structure is automatically updated when you create or delete model instances, or change an instance's parent.
Each level of the tree is automatically sorted by a field (or fields) of your choice.
New model methods are added to each registered model for:
- changing position in the tree
- retrieving ancestors, siblings, descendants
- counting descendants
- other tree-related operations
TreeManagermanager is added to all registered models. This provides methods to:
- move nodes around a tree, or into a different tree
- insert a node anywhere in a tree
- rebuild the MPTT fields for the tree (useful when you do bulk updates outside of django)
Form fields for tree models.
Utility functions for tree models.
Template tags and filters for rendering trees.