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
25817	Unable to rename a field reference in foreign key 'to_field'	Simon Kelly	nobody	"Steps to reproduce:

1. Create a model with a foreign key referencing another model's field via the 'to_field' arg.
2. Generate the initial migration

{{{#!python
class Bar(models.Model):
    bar_id = models.CharField(max_length=255, db_index=True, unique=True)

class Bazz(models.Model):
    bar = models.ForeignKey(Bar, to_field='bar_id')
}}}

3. Rename the field referenced in 'to_field' and create a migration for the change

Rename 'bar_id' to 'external_id':
{{{#!python
class Bar(models.Model):
    external_id = models.CharField(max_length=255, db_index=True, unique=True)

class Bazz(models.Model):
    bar = models.ForeignKey(Bar, to_field='external_id') 
}}}

Migration:
{{{#!python
    operations = [
        migrations.RenameField(
            model_name='bar',
            old_name='bar_id',
            new_name='external_id',
        ),
        migrations.AlterField(
            model_name='bazz',
            name='bar',
            field=models.ForeignKey(to='form_processor.Bar', to_field=b'external_id'),
            preserve_default=True,
        ),
    ]
}}}

4. Run the migration 

Error:
{{{
Traceback (most recent call last):
  File ""./manage.py"", line 73, in <module>
    execute_from_command_line(sys.argv)
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/core/management/__init__.py"", line 385, in execute_from_command_line
    utility.execute()
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/core/management/__init__.py"", line 377, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/core/management/base.py"", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/core/management/commands/sqlmigrate.py"", line 30, in execute
    return super(Command, self).execute(*args, **options)
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/core/management/base.py"", line 338, in execute
    output = self.handle(*args, **options)
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/core/management/commands/sqlmigrate.py"", line 61, in handle
    sql_statements = executor.collect_sql(plan)
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/db/migrations/executor.py"", line 82, in collect_sql
    migration.apply(project_state, schema_editor, collect_sql=True)
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/db/migrations/migration.py"", line 108, in apply
    operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/db/migrations/operations/fields.py"", line 139, in database_forwards
    schema_editor.alter_field(from_model, from_field, to_field)
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/db/backends/schema.py"", line 445, in alter_field
    old_db_params = old_field.db_parameters(connection=self.connection)
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/db/models/fields/related.py"", line 1787, in db_parameters
    return {""type"": self.db_type(connection), ""check"": []}
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/db/models/fields/related.py"", line 1778, in db_type
    rel_field = self.related_field
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/db/models/fields/related.py"", line 1684, in related_field
    return self.foreign_related_fields[0]
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/db/models/fields/related.py"", line 1442, in foreign_related_fields
    return tuple(rhs_field for lhs_field, rhs_field in self.related_fields)
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/db/models/fields/related.py"", line 1429, in related_fields
    self._related_fields = self.resolve_related_fields()
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/db/models/fields/related.py"", line 1422, in resolve_related_fields
    else self.rel.to._meta.get_field_by_name(to_field_name)[0])
  File ""/home/skelly/.virtualenvs/hq/local/lib/python2.7/site-packages/django/db/models/options.py"", line 420, in get_field_by_name
    % (self.object_name, name))
django.db.models.fields.FieldDoesNotExist: Bar has no field named 'bar_id'
}}}"	Bug	closed	Migrations	dev	Normal	fixed	to_field rename	Simon Charette	Ready for checkin	1	0	0	0	0	0