how to to Handle Unique Constraints with Multiple Related Models in Django 4.2
I'm integrating two systems and I'm stuck on something that should probably be simple... I'm working with an scenario while trying to enforce unique constraints across multiple related models in Django 4.2. I have two models, `Author` and `Book`, where each `Book` must have a unique title per `Author`. However, when I try to save a `Book` instance, I get an integrity behavior, even when the title is unique for that author. I've set up my models like this: ```python class Author(models.Model): name = models.CharField(max_length=100) class Book(models.Model): title = models.CharField(max_length=200) author = models.ForeignKey(Author, on_delete=models.CASCADE) class Meta: unique_together = ('title', 'author') ``` When I attempt to create a `Book` like so: ```python author = Author.objects.create(name='Jane Doe') book1 = Book.objects.create(title='Django for Beginners', author=author) book2 = Book(title='Django for Beginners', author=author) # This should be valid book2.save() ``` Unfortunately, I encounter the following behavior: ``` IntegrityError: UNIQUE constraint failed: myapp_book (title, author_id) ``` I have tried to ensure that there is no existing `Book` with the same title for the `Author` before saving, but the behavior continues when I try to save `book2`. I also checked the database directly, and there are no duplicates. I've tried using Django's `clean` method in the `Book` model to check for existing titles, but it doesn't seem to be the right approach since the behavior gets raised before that. Any insights into how I can enforce this unique constraint correctly or any alternative approaches would be greatly appreciated! Am I missing something obvious? I'm working on a API that needs to handle this. Any ideas what could be causing this? I'd be grateful for any help. I've been using Python for about a year now. What's the best practice here? Has anyone else encountered this?