Many to many only with explicit through models?

[stephan0h]

Regarding the tracking of many-to-many relationships: I gather from the documentation (https://django-pghistory.readthedocs.io/en/3.8.0/event_tracking/#many-to-many-fields) that the through model has to be declared explicitly for pghistory to track these. Just having a ManyToManyField in a model won't be enough. Am I right?

[wesleykendall]

The through model does not have to be declared explicitly, but the tracking model does.

Here is the example from the docs you linked, but with the models declared:

class Group(models.Model):
    ...

class User(models.Model):
    groups = models.ManyToMany(Group)


@pghistory.track(
    pghistory.AfterInsert("group.add"),
    pghistory.BeforeDelete("group.remove"),
    obj_field=None,
)
class UserGroups(User.groups.through):
    class Meta:
        proxy = True

In other words, we don't have to declare an explicit through model on groups like this example in the Django docs. However, in order for pghistory to track the auto-generated M2M model, one must declare a tracker on a proxy model like above.

Hope this distinction makes sense. I was unable to support pghistory.track(User.groups.through). There's something about Django's auto-generated M2M models that caused issues when trying to support it, hence the proxy model workaround

[stephan0h]

Thanks for the clarification - works!