atul-bhouraskar / django-mptt

Utilities for implementing a modified pre-order traversal tree in django.

django-mptt

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/

Documentation: http://django-mptt.github.com/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

What is django-mptt?

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.

Feature overview

• 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
• A TreeManager manager 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.