Question

How can I get a list of all the model objects that have a ForeignKey pointing to an object? (Something like the delete confirmation page in the Django admin before DELETE CASCADE).

I’m trying to come up with a generic way of merging duplicate objects in the database. Basically I want all of the objects that have ForeignKeys points to object “B” to be updated to point to object “A” so I can then delete “B” without losing anything important.

Thanks for your help!

Answer 1

Django <= 1.7

This gives you the property names for all related objects:

links = [rel.get_accessor_name() for rel in a._meta.get_all_related_objects()]

You can then use something like this to get all related objects:

for link in links:
    objects = getattr(a, link).all()
    for object in objects:
        # do something with related object instance

I spent a while trying to figure this out so I could implement a kind of “Observer Pattern” on
one of my models. Hope it’s helpful.

Django 1.8+

Use _meta.get_fields(): https://docs.djangoproject.com/en/1.10/ref/models/meta/#django.db.models.options.Options.get_fields (see reverse in the _get_fields() source also)