Deletion error of model with generic relation to inherited model

[ramusus]

I found that if we have 2 simple models connected by GenericRelation:

from django.contrib.comments.models import Comment
class NewComment(Comment):
    title = models.CharField(max_length=60)

class PersonWithComments(models.Model):
    comments = generic.GenericRelation(NewComment, object_id_field='object_pk')

It's impossible to delete PersonWithComments instance. With postgresql_psycopg2 and mysql DB drivers I always get error:

Traceback (most recent call last):
  File "/home/ram/PycharmProjects/m/web_site/generic/tests.py", line 75, in test_inherited_models_delete
    p.delete()
  File "/home/ram/PycharmProjects/m/web_site/django/db/models/base.py", line 610, in delete
    delete_objects(seen_objs, using)
  File "/home/ram/PycharmProjects/m/web_site/django/db/models/query.py", line 1282, in delete_objects
    del_query.delete_batch_related(pk_list, using=using)
  File "/home/ram/PycharmProjects/m/web_site/django/db/models/sql/subqueries.py", line 69, in delete_batch_related
    self.do_query(f.m2m_db_table(), where, using=using)
  File "/home/ram/PycharmProjects/m/web_site/django/db/models/sql/subqueries.py", line 27, in do_query
    self.get_compiler(using).execute_sql(None)
  File "/home/ram/PycharmProjects/m/web_site/django/db/models/sql/compiler.py", line 727, in execute_sql
    cursor.execute(sql, params)
  File "/home/ram/PycharmProjects/m/web_site/django/db/backends/postgresql_psycopg2/base.py", line 44, in execute
    return self.cursor.execute(query, args)
DatabaseError: column "object_pk" does not exist
LINE 1: DELETE FROM "generic_newcomment" WHERE ("object_pk" IN (E'23...

With sqlite3 everithing is ok! I don't know, may be this issue related to ​http://code.djangoproject.com/ticket/11263, but there tells nothing about deleting.

This error appears because fields 'object_pk' and 'content_type' are not in NewComment, they are in Comment model from Comments app. And there is no checks for these fields inside ContentTypes apps.

I attach tests for recreating this issue and patch for solving it.

[ramusus]

tests for recreating error

[ramusus]

patch for solving issue

[Russell Keith-Magee]

If I'm understanding the patch correctly, most of the change to m2m_table_name() is to discover the name of the model on which the object_id_field and content_type_field are located. This can be replaced by using a call to get_fields_with_model(). This returns tuples of (field, model) that describe the actual model on which fields can be found without the need to manually traverse the model heirarchy.

[ramusus]

Update patch with respect to russellm comment (ver 2)

[Aymeric Augustin]

Change UI/UX from NULL to False.

[Aymeric Augustin]

Change Easy pickings from NULL to False.

[Ramiro Morales]

See also #12885.

[Ramiro Morales]

Updated the proposed fix to current master: ​https://github.com/ramiro/django/compare/13203

There isn't actually need of running any test code. Just by providing a models design like the one added in the patch is enough to get the syncdb process to the test DB to crash under Postgres because of invalid DDL:

$ ~/django_test/pg84 generic_relations_regress -v2
Python version: 3.3.0 (default, Oct  7 2012, 14:43:21)
[GCC 4.6.3]
Importing application generic_relations_regress
Creating test database for alias 'default' ('test_django_default')...
Creating tables ...
Creating table django_content_type
Creating table auth_permission
Creating table auth_group_permissions
Creating table auth_group
Creating table auth_user_groups
Creating table auth_user_user_permissions
Creating table auth_user
Creating table django_site
Creating table django_flatpage_sites
Creating table django_flatpage
Creating table django_redirect
Creating table django_session
Creating table django_comments
Creating table django_comment_flags
Creating table django_admin_log
Creating table generic_relations_regress_link
Creating table generic_relations_regress_place
Creating table generic_relations_regress_restaurant
Creating table generic_relations_regress_address
Creating table generic_relations_regress_person
Creating table generic_relations_regress_charlink
Creating table generic_relations_regress_textlink
Creating table generic_relations_regress_oddrelation1
Creating table generic_relations_regress_oddrelation2
Creating table generic_relations_regress_note
Creating table generic_relations_regress_contact
Creating table generic_relations_regress_organization_contacts
Creating table generic_relations_regress_organization
Creating table generic_relations_regress_company
Creating table generic_relations_regress_reference
Creating table generic_relations_regress_venue
Installing custom SQL ...
Installing indexes ...
Traceback (most recent call last):
  File "django/upstream/django/db/backends/postgresql_psycopg2/base.py", line 54, in execute
    return self.cursor.execute(query, args)
psycopg2.ProgrammingError: column "id" of relation "generic_relations_regress_reference" does not exist


During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "django/upstream/django/core/management/commands/flush.py", line 62, in handle_noargs
    cursor.execute(sql)
  File "django/upstream/django/db/backends/postgresql_psycopg2/base.py", line 58, in execute
    six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2])
  File "django/upstream/django/utils/six.py", line 312, in reraise
    raise value.with_traceback(tb)
  File "django/upstream/django/db/backends/postgresql_psycopg2/base.py", line 54, in execute
    return self.cursor.execute(query, args)
django.db.utils.DatabaseError: column "id" of relation "generic_relations_regress_reference" does not exist


During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "./runtests.py", line 323, in <module>
    options.failfast, args)
  File "./runtests.py", line 166, in django_tests
    failures = test_runner.run_tests(test_labels, extra_tests=extra_tests)
  File "django/upstream/django/test/simple.py", line 368, in run_tests
    old_config = self.setup_databases()
  File "django/upstream/django/test/simple.py", line 316, in setup_databases
    self.verbosity, autoclobber=not self.interactive)
  File "django/upstream/django/db/backends/creation.py", line 305, in create_test_db
    database=self.connection.alias)
  File "django/upstream/django/core/management/__init__.py", line 161, in call_command
    return klass.execute(*args, **defaults)
  File "django/upstream/django/core/management/base.py", line 255, in execute
    output = self.handle(*args, **options)
  File "django/upstream/django/core/management/base.py", line 385, in handle
    return self.handle_noargs(**options)
  File "django/upstream/django/core/management/commands/flush.py", line 70, in handle_noargs
    The full error: %s""" % (connection.settings_dict['NAME'], e))
django.core.management.base.CommandError: Database test_django_default couldn't be flushed. Possible reasons:
  * The database isn't running or isn't configured correctly.
  * At least one of the expected database tables doesn't exist.
  * The SQL was invalid.
Hint: Look at the output of 'django-admin.py sqlflush'. That's the SQL this command wasn't able to run.
The full error: column "id" of relation "generic_relations_regress_reference" does not exist

[Ramiro Morales]

See also #9501.

[Ramiro Morales]

#18297 was closed as duplicate of this.

[Tim Graham]

It seems this was fixed in Django 1.6 by 97774429aeb54df4c09895c07cd1b09e70201f7d. I've added ​a regression test.

[Simon Charette]

The added test covers the reported use cases, LGTM given the tests pass.

[Tim Graham <timograham@…>]

In 58c7ff3:

Refs #13203, #9501 -- Added a test for generic relations to child models.

Fixed in 97774429aeb54df4c09895c07cd1b09e70201f7d.