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# from https://djangosnippets.org/snippets/2283/
from django.db import transaction
from django.db.models import get_models, Model
from django.contrib.contenttypes.fields import GenericForeignKey
@transaction.atomic
def merge_model_objects(primary_object, alias_objects=[], keep_old=False):
"""
Use this function to merge model objects (i.e. Users, Organizations, Polls,
etc.) and migrate all of the related fields from the alias objects to the
primary object.
Usage:
from django.contrib.auth.models import User
primary_user = User.objects.get(email='good_email@example.com')
duplicate_user = User.objects.get(email='good_email+duplicate@example.com')
merge_model_objects(primary_user, duplicate_user)
"""
MERGE_FIELDS = ('merge_candidate', 'merge_exclusion')
if not isinstance(alias_objects, list):
alias_objects = [alias_objects]
# check that all aliases are the same class as primary one and that
# they are subclass of model
primary_class = primary_object.__class__
if not issubclass(primary_class, Model):
raise TypeError('Only django.db.models.Model subclasses can be merged')
for alias_object in alias_objects:
if not isinstance(alias_object, primary_class):
raise TypeError('Only models of same class can be merged')
# Get a list of all GenericForeignKeys in all models
# TODO: this is a bit of a hack, since the generics framework should
# provide a similar
# method to the ForeignKey field for accessing the generic related fields.
generic_fields = []
for model in get_models():
for field_name, field in filter(lambda x: isinstance(
x[1], GenericForeignKey), model.__dict__.iteritems()):
generic_fields.append(field)
blank_local_fields = set()
for field in primary_object._meta.local_fields:
value = getattr(primary_object, field.attname)
# string fields with only spaces are empty fields
if isinstance(value, unicode) or isinstance(value, str):
value = value.strip()
if value in [None, '']:
blank_local_fields.add(field.attname)
# Loop through all alias objects and migrate their data to the primary
# object.
for alias_object in alias_objects:
# Migrate all foreign key references from alias object to primary
# object.
for related_object in alias_object._meta.get_all_related_objects():
# The variable name on the alias_object model.
alias_varname = related_object.get_accessor_name()
# The variable name on the related model.
obj_varname = related_object.field.name
related_objects = getattr(alias_object, alias_varname)
for obj in related_objects.all():
setattr(obj, obj_varname, primary_object)
obj.save()
# Migrate all many to many references from alias object to primary
# object.
related_many_objects = \
alias_object._meta.get_all_related_many_to_many_objects()
related_many_object_names = set()
for related_many_object in related_many_objects:
alias_varname = related_many_object.get_accessor_name()
obj_varname = related_many_object.field.name
if alias_varname in MERGE_FIELDS or obj_varname in MERGE_FIELDS:
continue
if alias_varname is not None:
# standard case
related_many_objects = getattr(
alias_object, alias_varname).all()
related_many_object_names.add(alias_varname)
else:
# special case, symmetrical relation, no reverse accessor
related_many_objects = getattr(alias_object, obj_varname).all()
related_many_object_names.add(obj_varname)
for obj in related_many_objects.all():
getattr(obj, obj_varname).remove(alias_object)
getattr(obj, obj_varname).add(primary_object)
# Migrate local many to many references from alias object to primary
# object.
for many_to_many_object in alias_object._meta.many_to_many:
alias_varname = many_to_many_object.get_attname()
if alias_varname in related_many_object_names or \
alias_varname in MERGE_FIELDS:
continue
many_to_many_objects = getattr(alias_object, alias_varname).all()
if alias_varname in blank_local_fields:
blank_local_fields.pop(alias_varname)
for obj in many_to_many_objects.all():
getattr(alias_object, alias_varname).remove(obj)
getattr(primary_object, alias_varname).add(obj)
# Migrate all generic foreign key references from alias object to
# primary object.
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)
for generic_related_object in field.model.objects.filter(
**filter_kwargs):
setattr(generic_related_object, field.name, primary_object)
generic_related_object.save()
# Try to fill all missing values in primary object by values of
# duplicates
filled_up = set()
for field_name in blank_local_fields:
val = getattr(alias_object, field_name)
if val not in [None, '']:
setattr(primary_object, field_name, val)
filled_up.add(field_name)
blank_local_fields -= filled_up
if not keep_old:
alias_object.delete()
primary_object.save()
return primary_object
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