Adding constraints validations to a model

We want to make sure that our models do not have invalid or inconsistent data. Odoo has two kinds of constraints to do this:

• Database-level constraints: These are the constraints that PostgreSQL supports. The most common ones are the UNIQUE constraints, which prevent duplicate values. We can also use CHECK and EXCLUDE constraints for other conditions. These constraints are fast and reliable, but they are limited by what PostgreSQL can do.
• Server-level constraints: These are the constraints that we write in Python code. We can use these constraints when the database-level ones are not enough for our needs. These constraints are more flexible and powerful, but they are slower and more complex.

Getting ready

We will continue using the my_hostel add-on module from the previous recipe. We will use the hostel room model and add some constraints to it. We will use the hostel room model from Chapter 3, Creating Odoo Add-On Modules...