Refs #18012 -- Removed special casing for proxy models deletion.

from collections import Counter, OrderedDict

from itertools import chain

from operator import attrgetter

from django.db import IntegrityError, connections, transaction

def get_candidate_relations_to_delete(opts):

    # Collect models that contain candidate relations to delete. This may include

    # relations coming from proxy models.

    candidate_models = {opts}

    candidate_models = candidate_models.union(opts.concrete_model._meta.proxied_children)

    # For each model, get all candidate fields.

    candidate_model_fields = chain.from_iterable(

        opts.get_fields(include_hidden=True) for opts in candidate_models

    )

    # The candidate relations are the ones that come from N-1 and 1-1 relations.

    # N-N  (i.e., many-to-many) relations aren't candidates for deletion.

    return (

        f for f in candidate_model_fields

        f for f in opts.get_fields(include_hidden=True)

        if f.auto_created and not f.concrete and (f.one_to_one or f.one_to_many)

    )