Nested Sets trees
=================
.. module:: treebeard.ns_tree
.. moduleauthor:: Gustavo Picon <tabo@tabo.pe>
An implementation of Nested Sets trees for Django 1.0+, as described by
`Joe Celko`_ in `Trees and Hierarchies in SQL for Smarties`_.
Nested sets have very efficient reads at the cost of high maintenance on
write/delete operations.
.. _`Joe Celko`: http://en.wikipedia.org/wiki/Joe_Celko
.. _`Trees and Hierarchies in SQL for Smarties`:
http://www.elsevier.com/wps/product/cws_home/702605
.. inheritance-diagram:: NS_Node
.. autoclass:: NS_Node
:show-inheritance:
.. attribute:: node_order_by
Attribute: a list of model fields that will be used for node
ordering. When enabled, all tree operations will assume this ordering.
Example::
node_order_by = ['field1', 'field2', 'field3']
.. attribute:: depth
``PositiveIntegerField``, depth of a node in the tree. A root node
has a depth of *1*.
.. attribute:: lft
``PositiveIntegerField``
.. attribute:: rgt
``PositiveIntegerField``
.. attribute:: tree_id
``PositiveIntegerField``
.. automethod:: get_tree
See: :meth:`treebeard.Node.get_tree`
.. note::
This metod returns a queryset.
