id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
26105	create_permissions uses ContentType cache which contains non-existing pks	Sven R. Kunze	nobody	"While migrating a larger project, we found the traceback attached.

We found that create_permissions from {{{django/contrib/auth/management/__init__.py}}} uses the {{{ ContentType.objects._cache }}} instead of querying the database for the real pk of the contenttype.


Real pks from database:
{{{
 id  |       app_label       |                   model                    
-----+-----------------------+--------------------------------------------
   1 | auth                  | permission
   2 | auth                  | group
   3 | auth                  | user
}}}

Pks generated by django (execution at breakpoint at line 103):
{{{
>>> [(id, ct) for id, ct in ContentType.objects._cache['default'].items() if ct.app_label == 'auth']
[
    (2, <ContentType: group>),
    (3, <ContentType: permission>),
    (4, <ContentType: user>),
]
}}}


It seems Django confused real pks with imaginary pks. We created a placeholder contenttype with pk=4 before rerunning the migrations, which fixed the exception but created a new permission linked to this ""false"" contenttype.

If the contenttype with pk=4 were a real one (i.e. an existing model etc.), a wrong permission would have been created then.

{{{
=> select * from django_content_type where id=4;
 id | app_label |     model     
----+-----------+---------------
  4 | auth      | XXXXXXXXXXXXX

=> select * from auth_permission where content_type_id=4;
 id  |      name       | content_type_id |  codename   
-----+-----------------+-----------------+-------------
 598 | Can delete user |               4 | delete_user
 597 | Can change user |               4 | change_user
 596 | Can add user    |               4 | add_user
}}}

The migration traceback:
{{{
Traceback (most recent call last):
  File ""lib/python2.7/site-packages/django/core/management/__init__.py"", line 354, in execute_from_command_line
    utility.execute()
  File ""lib/python2.7/site-packages/django/core/management/__init__.py"", line 346, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File ""lib/python2.7/site-packages/django/core/management/base.py"", line 394, in run_from_argv
    self.execute(*args, **cmd_options)
  File ""lib/python2.7/site-packages/django/core/management/base.py"", line 445, in execute
    output = self.handle(*args, **options)
  File ""lib/python2.7/site-packages/django/core/management/commands/migrate.py"", line 226, in handle
    emit_post_migrate_signal(created_models, self.verbosity, self.interactive, connection.alias)
  File ""lib/python2.7/site-packages/django/core/management/sql.py"", line 280, in emit_post_migrate_signal
    using=db)
  File ""lib/python2.7/site-packages/django/dispatch/dispatcher.py"", line 189, in send
    response = receiver(signal=self, sender=sender, **named)
  File ""lib/python2.7/site-packages/django/contrib/auth/management/__init__.py"", line 114, in create_permissions 
    Permission.objects.using(using).bulk_create(perms)
  File ""lib/python2.7/site-packages/django/db/models/query.py"", line 392, in bulk_create
    self._batched_insert(objs_without_pk, fields, batch_size)
  File ""lib/python2.7/site-packages/django/db/transaction.py"", line 225, in __exit__
    connection.commit() 
  File ""lib/python2.7/site-packages/django/db/backends/base/base.py"", line 173, in commit
    self._commit() 
  File ""lib/python2.7/site-packages/django/db/backends/base/base.py"", line 142, in _commit
    return self.connection.commit()
  File ""lib/python2.7/site-packages/django/db/utils.py"", line 98, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File ""lib/python2.7/site-packages/django/db/backends/base/base.py"", line 142, in _commit
    return self.connection.commit()
django.db.utils.IntegrityError: insert or update on table ""auth_permission"" violates foreign key constraint ""auth_content_type_id_508cf46651277a81_fk_django_content_type_id""
DETAIL:  Key (content_type_id)=(4) is not present in table ""django_content_type"".
}}}"	Bug	closed	Database layer (models, ORM)	1.8	Normal	duplicate		tzanke@…	Unreviewed	0	0	0	0	0	0