======== Overview

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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's a good article 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: https://www.ibase.ru/files/articles/programming/dbmstrees/sqltrees.html .. _Storing Hierarchical Data in a Database: https://www.sitepoint.com/hierarchical-data-database/ .. _Managing Hierarchical Data in MySQL: http://mikehillyer.com/articles/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.

• Translations for:

  • Danish
  • French
  • German
  • Polish