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
22342	"Changing a model to an abstract model caused ""ValueError: Related model 'app.Model' cannot be resolved"""	Daniel Hahler	nobody	"I have just run into an error with `migrate`.

I had turned an existing model (which had a database table already) into a abstract base for others.

The generated migration was, and removing it from the migration worked around the problem:

{{{
migrations.DeleteModel(
    name='Model',
),
}}}


{{{
  Applying app.0016_auto_20140326_1723...Traceback (most recent call last):
  File ""…/manage.py"", line 62, in <module>
    execute_from_command_line(sys.argv)
  File ""…/django-master/django/core/management/__init__.py"", line 427, in execute_from_command_line
    utility.execute()
  File ""…/django-master/django/core/management/__init__.py"", line 419, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File ""…/django-master/django/core/management/base.py"", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File ""…/django-master/django/core/management/base.py"", line 337, in execute
    output = self.handle(*args, **options)
  File ""…/django-master/django/core/management/commands/migrate.py"", line 145, in handle
    executor.migrate(targets, plan, fake=options.get(""fake"", False))
  File ""…/django-master/django/db/migrations/executor.py"", line 60, in migrate
    self.apply_migration(migration, fake=fake)
  File ""…/django-master/django/db/migrations/executor.py"", line 94, in apply_migration
    migration.apply(project_state, schema_editor)
  File ""…/django-master/django/db/migrations/migration.py"", line 97, in apply
    operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
  File ""…/django-master/django/db/migrations/operations/fields.py"", line 83, in database_forwards
    schema_editor.remove_field(from_model, from_model._meta.get_field_by_name(self.name)[0])
  File ""…/django-master/django/db/backends/schema.py"", line 443, in remove_field
    if field.db_parameters(connection=self.connection)['type'] is None:
  File ""…/django-master/django/db/models/fields/related.py"", line 1758, in db_parameters
    return {""type"": self.db_type(connection), ""check"": []}
  File ""…/django-master/django/db/models/fields/related.py"", line 1749, in db_type
    rel_field = self.related_field
  File ""…/django-master/django/db/models/fields/related.py"", line 1655, in related_field
    return self.foreign_related_fields[0]
  File ""…/django-master/django/db/models/fields/related.py"", line 1414, in foreign_related_fields
    return tuple(rhs_field for lhs_field, rhs_field in self.related_fields)
  File ""…/django-master/django/db/models/fields/related.py"", line 1401, in related_fields
    self._related_fields = self.resolve_related_fields()
  File ""…/django-master/django/db/models/fields/related.py"", line 1386, in resolve_related_fields
    raise ValueError('Related model %r cannot be resolved' % self.rel.to)
ValueError: Related model 'app.Model' cannot be resolved
}}}

It might be somewhat related to bug #22319."	Bug	closed	Migrations	dev	Normal	worksforme			Unreviewed	0	0	0	0	0	0