"""
Handles the merging of two or more model instances.
Adapted from the django-extensions package:
https://github.com/django-extensions/django-extensions
"""
from django.apps import apps
from django.contrib.contenttypes.fields import GenericForeignKey
from django.db import transaction
from uniauth.utils import get_setting
def _get_generic_fields():
"""
Return a list of all GenericForeignKeys in all models.
"""
generic_fields = []
for model in apps.get_models():
for field_name, field in model.__dict__.items():
if isinstance(field, GenericForeignKey):
generic_fields.append(field)
return generic_fields
@transaction.atomic()
def merge_model_instances(primary_object, alias_objects, field_trace=[]):
"""
Merge several model instances into one, the `primary_object`.
Use this function to merge model objects and migrate all of the
related fields from the alias objects into the primary object.
Performs recursive merging of related One-to-One fields.
"""
generic_fields = _get_generic_fields()
# get related fields
related_fields = list(filter(
lambda x: x.is_relation is True,
primary_object._meta.get_fields()))
many_to_many_fields = list(filter(
lambda x: x.many_to_many is True, related_fields))
related_fields = list(filter(
lambda x: x.many_to_many is False, related_fields))
# Loop through all alias objects and migrate their references to the
# primary object
deleted_objects = []
deleted_objects_count = 0
for alias_object in alias_objects:
# Migrate all foreign key references from alias object to primary
# object.
for many_to_many_field in many_to_many_fields:
alias_varname = many_to_many_field.name
related_objects = getattr(alias_object, alias_varname, None)
if related_objects is None:
continue
for obj in related_objects.all():
try:
# Handle regular M2M relationships.
getattr(alias_object, alias_varname).remove(obj)
getattr(primary_object, alias_varname).add(obj)
except AttributeError:
# Handle M2M relationships with a 'through' model.
# This does not delete the 'through model.
through_model = getattr(alias_object, alias_varname).through
kwargs = {
many_to_many_field.m2m_reverse_field_name(): obj,
many_to_many_field.m2m_field_name(): alias_object,
}
through_model_instances = through_model.objects.filter(**kwargs)
for instance in through_model_instances:
# Re-attach the through model to the primary_object
setattr(
instance,
many_to_many_field.m2m_field_name(),
primary_object)
instance.save()
for related_field in related_fields:
if related_field.one_to_many:
alias_varname = related_field.get_accessor_name()
related_objects = getattr(alias_object, alias_varname, None)
if related_objects is None:
continue
for obj in related_objects.all():
field_name = related_field.field.name
setattr(obj, field_name, primary_object)
obj.save()
elif related_field.one_to_one or related_field.many_to_one:
alias_varname = related_field.name
related_object = getattr(alias_object, alias_varname, None)
primary_related_object = getattr(primary_object,
alias_varname, None)
if related_object is None:
continue
elif primary_related_object is None:
setattr(primary_object, alias_varname, related_object)
primary_object.save()
elif related_field.one_to_one:
# Perform recursive merging for one-to-one fields
if get_setting("UNIAUTH_PERFORM_RECURSIVE_MERGING"):
if related_field in field_trace:
continue
updated_trace = field_trace + [related_field,
related_field.remote_field]
merge_model_instances(primary_related_object,
[related_object], updated_trace)
else:
related_object.delete()
for field in generic_fields:
filter_kwargs = {}
filter_kwargs[field.fk_field] = alias_object._get_pk_val()
filter_kwargs[field.ct_field] = field.get_content_type(alias_object)
related_objects = field.model.objects.filter(**filter_kwargs)
for generic_related_object in related_objects:
setattr(generic_related_object, field.name, primary_object)
generic_related_object.save()
if alias_object.id:
deleted_objects += [alias_object]
alias_object.delete()
deleted_objects_count += 1
return primary_object, deleted_objects, deleted_objects_count
