Adding a hierarchy to a model

You can use an m2o field to represent hierarchies, where each record has a parent record and many child records in the same model. However, Odoo also provides improved support for this type of field by using the nested set model (https://en.wikipedia.org/wiki/Nested_set_model). When activated, queries using the child_of operator in their domain filters will run significantly faster.

Staying with the Hostel example, we will build a hierarchical category tree that can be used to categorize hostels.

Getting ready

We will continue using the my_hostel add-on module from the previous recipe.

How to do it...

We will add a new Python file, models/hostel_categ.py, for the category tree, as follows:

1. To load the new Python code file, add the following line to models/__init__.py:

   from . import hostel_categ

2. To create the Hostel Category model with the parent and child relationships, create the models/hostel_categ.py file with the following...