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
23983	Cannot Alter order_with_respect_to after there is already data in a table	James Pulec	Andriy Sokolovskiy	"Due to the way that migration operation 'AlterOrderWithRespectTo' is implemented, it will not set a default for the '_order' column it tries to create. Because of this, it is not possible to change 'order_with_respect_to' once there is already data in your database, since the SQL it generates is 'ALTER TABLE ""test_app_eggs"" ADD COLUMN ""_order"" integer NOT NULL;'.


Inital models:
{{{
from django.db import models

# Create your models here.


class Spam(models.Model):
    name = models.CharField(max_length=200)


class Eggs(models.Model):
    spam = models.ForeignKey('test_app.Spam')
    name = models.CharField(max_length=200)

}}}

Then add some data, and change the models to:


{{{
from django.db import models

# Create your models here.


class Spam(models.Model):
    name = models.CharField(max_length=200)


class Eggs(models.Model):
    spam = models.ForeignKey('test_app.Spam')
    name = models.CharField(max_length=200)

    class Meta:
        order_with_respect_to = 'spam'

}}}

and then make migrations and try to migrate results in the following traceback:


{{{
(test_project)~/test_project/test_project: $ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, test_app, contenttypes, auth, sessions
Running migrations:
  Applying test_app.0002_auto_20141211_2202...Traceback (most recent call last):
  File ""manage.py"", line 10, in <module>
    execute_from_command_line(sys.argv)
  File ""/home/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/core/management/__init__.py"", line 385, in execute_from_command_line
    utility.execute()
  File ""/home/james/.virtualenvs/test_project/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/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/core/management/base.py"", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File ""/home/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/core/management/base.py"", line 338, in execute
    output = self.handle(*args, **options)
  File ""/home/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py"", line 160, in handle
    executor.migrate(targets, plan, fake=options.get(""fake"", False))
  File ""/home/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/db/migrations/executor.py"", line 63, in migrate
    self.apply_migration(migration, fake=fake)
  File ""/home/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/db/migrations/executor.py"", line 97, in apply_migration
    migration.apply(project_state, schema_editor)
  File ""/home/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/db/migrations/migration.py"", line 107, in apply
    operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
  File ""/home/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/db/migrations/operations/models.py"", line 328, in database_forwards
    field,
  File ""/home/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/db/backends/schema.py"", line 390, in add_field
    self.execute(sql, params)
  File ""/home/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/db/backends/schema.py"", line 99, in execute
    cursor.execute(sql, params)
  File ""/home/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/db/backends/utils.py"", line 81, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File ""/home/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/db/backends/utils.py"", line 65, in execute
    return self.cursor.execute(sql, params)
  File ""/home/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/db/utils.py"", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File ""/home/james/.virtualenvs/test_project/local/lib/python2.7/site-packages/django/db/backends/utils.py"", line 65, in execute
    return self.cursor.execute(sql, params)
django.db.utils.IntegrityError: column ""_order"" contains null values
}}}
"	Bug	closed	Migrations	1.7	Normal	fixed			Accepted	1	0	0	0	0	0