django-tree-queries 0.1.0

Tree queries with explicit opt-in, without configurability

Query Django model trees using adjacency lists and recursive common table expressions. Supports PostgreSQL, sqlite3 (3.8.3 or higher) and MariaDB (10.2.2 or higher), maybe also MySQL 8.0 but I found no easy way to test against it.

Supports Django 1.11 or better, Python 2.7 and 3.4 or better.

Features and limitations

• Supports only integer primary keys.
• Allows adding an integer field to order nodes on a given level.
• Uses the correct definition of depth, where root nodes have a depth of zero.
• Only supports 10 levels of nodes on MariaDB.
• Only supports maximum primary key values of 16^9 on sqlite3 and MariaDB (this may change if the database engines implement proper array support).
• The parent foreign key must be named "parent" at the moment (but why would you want to name it differently?)
• The fields added by the common table expression always are tree_depth, tree_path and tree_ordering. The names cannot be changed. The first field is always an integer, the other fields are lists of integers.
• Besides adding the fields mentioned above the package only adds queryset methods for filtering ancestors and descendants. Other features may be useful, but will not be added to the package just because it’s possible to do so.
• Little code, and relatively simple when compared to other tree management solutions for Django.

Usage

• Install django-tree-queries using pip.
• Extend tree_queries.models.TreeNode or build your own queryset and/or manager using tree_queries.query.TreeQuerySet The TreeNode abstract model already contains a parent foreign key for your convenience.
• Call the with_tree_fields() queryset method if you require the additional fields respectively the CTE.
• Until documentation is more complete I’ll have to refer you to the test suite for additional instructions and usage examples.