django-pgtrigger provides primitives for configuring
on Django models.
Triggers can solve a wide variety of database-level problems more elegantly and reliably than in the application-level of Django. Here are some common problems that can be solved with triggers, many of which we later show how to solve in the docs:
Protecting updates and deletes or rows or columns (
Soft deleting models by setting a field to a value on delete (
Tracking changes to models or columns change, or when specific conditions happen (django-pghistory uses
django-pgtriggerto do this).
Keeping fields in sync with other fields.
Ensuring that engineers use an official interface (e.g. engineers must use
Only allowing a status field of a model to transition through certain states (
pip install django-pgtrigger and
Users declare the plpgsql code manually
pgtrigger.Trigger object or can use the derived triggers in
django-pgtrigger that implement common scenarios. For example,
pgtrigger.Protect can protect operations on a model, such as deletions:
from django.db import models import pgtrigger @pgtrigger.register( pgtrigger.Protect(name='protect_deletes', operation=pgtrigger.Delete) ) class CannotBeDeletedModel(models.Model): """This model cannot be deleted!"""
django-pgtrigger aims to alleviate the boilerplate of triggers and
having to write raw SQL by using common Django idioms. For example, users
pgtrigger.F objects to
conditionally execute triggers based on the
being modified. For example, let’s only protect deletes
against “active” rows of a model:
from django.db import models import pgtrigger @pgtrigger.register( pgtrigger.Protect( name='protect_deletes', operation=pgtrigger.Delete, # Protect deletes when the OLD row of the trigger is still active condition=pgtrigger.Q(old__is_active=True) ) ) class CannotBeDeletedModel(models.Model): """Active model object cannot be deleted!""" is_active = models.BooleanField(default=True)
pgtrigger.F, and derived
objects can solve a wide array of Django problems without ever having to
write raw SQL. Users, however, can still customize
triggers and write as much raw SQL as needed for their use case.
For a complete run-through of
django-pgtrigger and all derived
triggers (along with a trigger cookbook!), read the Tutorial.
After you have gone through the tutorial, check out https://wesleykendall.github.io/django-pgtrigger-tutorial/, which is an interactive tutorial written for a Django meetup talk about