👀 Views: 0 💬 Answers: 1 📅 Created: 2025-07-31

django signals bulk-update many-to-many Python

I've hit a wall trying to I've tried everything I can think of but I am experiencing unexpected behavior when trying to trigger signals for a Many-to-Many relationship after performing a bulk update using `update()` in Django 4.1... I've set up a `ManyToManyField` between `Author` and `Book` models, and I want to emit a signal whenever an author is added to a book. However, I noticed that the signal doesn't get called when I use `bulk_update()` or `update()`. For example, this is how I defined my models: ```python class Author(models.Model): name = models.CharField(max_length=100) class Book(models.Model): title = models.CharField(max_length=200) authors = models.ManyToManyField(Author) ``` I connected my signal as follows: ```python from django.db.models.signals import m2m_changed from django.dispatch import receiver @receiver(m2m_changed, sender=Book.authors.through) def authors_changed(sender, instance, action, **kwargs): print(f'Authors changed for book: {instance.title}, action: {action}') ``` When I add authors to a book using: ```python book = Book.objects.get(id=1) author = Author.objects.get(id=1) book.authors.add(author) ``` The signal works and I see the expected output. However, when I attempt to use `bulk_update()` like this: ```python book = Book.objects.get(id=1) book.authors.set([author]) # This line does not trigger the signal Book.objects.filter(id=1).update(title='New Title') ``` The signal is not triggered, and I do not see any output at all. I've confirmed that `bulk_update()` does not call the `m2m_changed` signal, but does anyone know if there's a recommended way to handle this situation? My intention is to ensure that any updates to the Many-to-Many relationship also trigger the necessary signals for downstream logic. Am I missing something, or is there a better approach that adheres to Django's best practices for handling Many-to-Many relationships? I've been using Python for about a year now. This is my first time working with Python stable. What would be the recommended way to handle this?