django.db.migrations.executor.MigrationExecutor - python examples

    def setUp(self):
        self.migrate_from = [self.migrate_from]
        self.migrate_to = [self.migrate_to]

        # Reverse to the original migration
        executor = MigrationExecutor(connection)
        executor.migrate(self.migrate_from)

        old_apps = executor.loader.project_state(self.migrate_from).apps
        self.setUpBeforeMigration(old_apps)

        # Run the migration to test
        executor.loader.build_graph()
        executor.migrate(self.migrate_to)

        self.apps = executor.loader.project_state(self.migrate_to).apps

    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_non_atomic"})
    def test_non_atomic_migration(self):
        """
        Applying a non-atomic migration works as expected.
        """
        executor = MigrationExecutor(connection)
        with self.astertRaisesMessage(RuntimeError, "Abort migration"):
            executor.migrate([("migrations", "0001_initial")])
        self.astertTableExists("migrations_publisher")
        migrations_apps = executor.loader.project_state(("migrations", "0001_initial")).apps
        Publisher = migrations_apps.get_model("migrations", "Publisher")
        self.astertTrue(Publisher.objects.exists())
        self.astertTableNotExists("migrations_book")

    @skipUnlessDBFeature('can_rollback_ddl')
    @override_settings(MIGRATION_MODULES={'migrations': 'migrations.test_migrations'})
    def test_migrations_applied_and_recorded_atomically(self):
        """Migrations are applied and recorded atomically."""
        executor = MigrationExecutor(connection)
        with mock.patch('django.db.migrations.executor.MigrationExecutor.record_migration') as record_migration:
            record_migration.side_effect = RuntimeError('Recording migration failed.')
            with self.astertRaisesMessage(RuntimeError, 'Recording migration failed.'):
                executor.migrate([('migrations', '0001_initial')])
        # The migration isn't recorded as applied since it failed.
        migration_recorder = MigrationRecorder(connection)
        self.astertFalse(migration_recorder.migration_qs.filter(app='migrations', name='0001_initial').exists())
        self.astertTableNotExists('migrations_author')

    def setUp(self):
        astert self.migrate_from and self.migrate_to, \
            "TestCase '{}' must define migrate_from and " \
            "migrate_to properties".format(type(self).__name__)
        self.migrate_from = [(self.app, self.migrate_from)]
        self.migrate_to = [(self.app, self.migrate_to)]
        executor = MigrationExecutor(connection)
        old_apps = executor.loader.project_state(self.migrate_from).apps

        # Reverse to the original migration
        executor.migrate(self.migrate_from)

        self.setUpBeforeMigration(old_apps)

        # Run the migration to test
        executor.loader.build_graph()
        executor.migrate(self.migrate_to)

        self.apps = executor.loader.project_state(self.migrate_to).apps

@api_view(['GET'])
@authentication_clastes(())
@permission_clastes((permissions.AllowAny,))
def health_check(request):
    """
    This endpoint (/health) returns 200 if no migrations are pending, else 503
    https://engineering.instawork.com/elegant-database-migrations-on-ecs-74f3487da99f
    """
    executor = MigrationExecutor(connections[DEFAULT_DB_ALIAS])
    plan = executor.migration_plan(executor.loader.graph.leaf_nodes())
    return HttpResponse(status=503 if plan else 200)

    def __init__(
        self,
        database: Optional[str] = None,
    ) -> None:
        """That's where we initialize all required internals."""
        if database is None:
            database = DEFAULT_DB_ALIAS

        self._database: str = database
        self._executor = MigrationExecutor(connections[self._database])

    def check_migrations(self):
        """
        Print a warning if the set of migrations on disk don't match the
        migrations in the database.
        """
        from django.db.migrations.executor import MigrationExecutor
        try:
            executor = MigrationExecutor(connections[DEFAULT_DB_ALIAS])
        except ImproperlyConfigured:
            # No databases are configured (or the dummy one)
            return
        except MigrationSchemaMissing:
            self.stdout.write(self.style.NOTICE(
                "\nNot checking migrations as it is not possible to access/create the django_migrations table."
            ))
            return

        plan = executor.migration_plan(executor.loader.graph.leaf_nodes())
        if plan:
            apps_waiting_migration = sorted(set(migration.app_label for migration, backwards in plan))
            self.stdout.write(
                self.style.NOTICE(
                    "\nYou have %(unpplied_migration_count)s unapplied migration(s). "
                    "Your project may not work properly until you apply the "
                    "migrations for app(s): %(apps_waiting_migration)s." % {
                        "unpplied_migration_count": len(plan),
                        "apps_waiting_migration": ", ".join(apps_waiting_migration),
                    }
                )
            )
            self.stdout.write(self.style.NOTICE("Run 'python manage.py migrate' to apply them.\n"))

    def handle(self, *args, **options):

        self.verbosity = options['verbosity']
        self.interactive = options['interactive']

        # Import the 'management' module within each installed app, to register
        # dispatcher events.
        for app_config in apps.get_app_configs():
            if module_has_submodule(app_config.module, "management"):
                import_module('.management', app_config.name)

        # Get the database we're operating from
        db = options['database']
        connection = connections[db]

        # Hook for backends needing any database preparation
        connection.prepare_database()
        # Work out which apps have migrations and which do not
        executor = MigrationExecutor(connection, self.migration_progress_callback)

        # Raise an error if any migrations are applied before their dependencies.
        executor.loader.check_consistent_history(connection)

        # Before anything else, see if there's conflicting apps and drop out
        # hard if there are any
        conflicts = executor.loader.detect_conflicts()
        if conflicts:
            name_str = "; ".join(
                "%s in %s" % (", ".join(names), app)
                for app, names in conflicts.items()
            )
            raise CommandError(
                "Conflicting migrations detected; multiple leaf nodes in the "
                "migration graph: (%s).\nTo fix them run "
                "'python manage.py makemigrations --merge'" % name_str
            )

        # If they supplied command line arguments, work out what they mean.
        target_app_labels_only = True
        if options['app_label'] and options['migration_name']:
            app_label, migration_name = options['app_label'], options['migration_name']
            if app_label not in executor.loader.migrated_apps:
                raise CommandError(
                    "App '%s' does not have migrations." % app_label
                )
            if migration_name == "zero":
                targets = [(app_label, None)]
            else:
                try:
                    migration = executor.loader.get_migration_by_prefix(app_label, migration_name)
                except AmbiguityError:
                    raise CommandError(
                        "More than one migration matches '%s' in app '%s'. "
                        "Please be more specific." %
                        (migration_name, app_label)
                    )
                except KeyError:
                    raise CommandError("Cannot find a migration matching '%s' from app '%s'." % (
                        migration_name, app_label))
                targets = [(app_label, migration.name)]
            target_app_labels_only = False
        elif options['app_label']:
            app_label = options['app_label']
            if app_label not in executor.loader.migrated_apps:
                raise CommandError(
                    "App '%s' does not have migrations." % app_label
                )
            targets = [key for key in executor.loader.graph.leaf_nodes() if key[0] == app_label]
        else:
            targets = executor.loader.graph.leaf_nodes()

        plan = executor.migration_plan(targets)
        run_syncdb = options['run_syncdb'] and executor.loader.unmigrated_apps

        # Print some useful info
        if self.verbosity >= 1:
            self.stdout.write(self.style.MIGRATE_HEADING("Operations to perform:"))
            if run_syncdb:
                self.stdout.write(
                    self.style.MIGRATE_LABEL("  Synchronize unmigrated apps: ") +
                    (", ".join(sorted(executor.loader.unmigrated_apps)))
                )
            if target_app_labels_only:
                self.stdout.write(
                    self.style.MIGRATE_LABEL("  Apply all migrations: ") +
                    (", ".join(sorted(set(a for a, n in targets))) or "(none)")
                )
            else:
                if targets[0][1] is None:
                    self.stdout.write(self.style.MIGRATE_LABEL(
                        "  Unapply all migrations: ") + "%s" % (targets[0][0], )
                    )
                else:
                    self.stdout.write(self.style.MIGRATE_LABEL(
                        "  Target specific migration: ") + "%s, from %s"
                        % (targets[0][1], targets[0][0])
                    )

        pre_migrate_state = executor._create_project_state(with_applied_migrations=True)
        pre_migrate_apps = pre_migrate_state.apps
        emit_pre_migrate_signal(
            self.verbosity, self.interactive, connection.alias, apps=pre_migrate_apps, plan=plan,
        )

        # Run the syncdb phase.
        if run_syncdb:
            if self.verbosity >= 1:
                self.stdout.write(self.style.MIGRATE_HEADING("Synchronizing apps without migrations:"))
            self.sync_apps(connection, executor.loader.unmigrated_apps)

        # Migrate!
        if self.verbosity >= 1:
            self.stdout.write(self.style.MIGRATE_HEADING("Running migrations:"))
        if not plan:
            if self.verbosity >= 1:
                self.stdout.write("  No migrations to apply.")
                # If there's changes that aren't in migrations yet, tell them how to fix it.
                autodetector = MigrationAutodetector(
                    executor.loader.project_state(),
                    ProjectState.from_apps(apps),
                )
                changes = autodetector.changes(graph=executor.loader.graph)
                if changes:
                    self.stdout.write(self.style.NOTICE(
                        "  Your models have changes that are not yet reflected "
                        "in a migration, and so won't be applied."
                    ))
                    self.stdout.write(self.style.NOTICE(
                        "  Run 'manage.py makemigrations' to make new "
                        "migrations, and then re-run 'manage.py migrate' to "
                        "apply them."
                    ))
            fake = False
            fake_initial = False
        else:
            fake = options['fake']
            fake_initial = options['fake_initial']
        post_migrate_state = executor.migrate(
            targets, plan=plan, state=pre_migrate_state.clone(), fake=fake,
            fake_initial=fake_initial,
        )
        # post_migrate signals have access to all models. Ensure that all models
        # are reloaded in case any are delayed.
        post_migrate_state.clear_delayed_apps_cache()
        post_migrate_apps = post_migrate_state.apps

        # Re-render models of real apps to include relationships now that
        # we've got a final state. This wouldn't be necessary if real apps
        # models were rendered with relationships in the first place.
        with post_migrate_apps.bulk_update():
            model_keys = []
            for model_state in post_migrate_apps.real_models:
                model_key = model_state.app_label, model_state.name_lower
                model_keys.append(model_key)
                post_migrate_apps.unregister_model(*model_key)
        post_migrate_apps.render_multiple([
            ModelState.from_model(apps.get_model(*model)) for model in model_keys
        ])

        # Send the post_migrate signal, so individual apps can do whatever they need
        # to do at this point.
        emit_post_migrate_signal(
            self.verbosity, self.interactive, connection.alias, apps=post_migrate_apps, plan=plan,
        )

    def handle(self, *args, **options):
        # Get the database we're operating from
        connection = connections[options['database']]

        # Load up an executor to get all the migration data
        executor = MigrationExecutor(connection)

        # Resolve command-line arguments into a migration
        app_label, migration_name = options['app_label'], options['migration_name']
        if app_label not in executor.loader.migrated_apps:
            raise CommandError("App '%s' does not have migrations" % app_label)
        try:
            migration = executor.loader.get_migration_by_prefix(app_label, migration_name)
        except AmbiguityError:
            raise CommandError("More than one migration matches '%s' in app '%s'. Please be more specific." % (
                migration_name, app_label))
        except KeyError:
            raise CommandError("Cannot find a migration matching '%s' from app '%s'. Is it in INSTALLED_APPS?" % (
                migration_name, app_label))
        targets = [(app_label, migration.name)]

        # Show begin/end around output only for atomic migrations
        self.output_transaction = migration.atomic

        # Make a plan that represents just the requested migrations and show SQL
        # for it
        plan = [(executor.loader.graph.nodes[targets[0]], options['backwards'])]
        sql_statements = executor.collect_sql(plan)
        return '\n'.join(sql_statements)

    def setUp(self):
        astert (
            self.migrate_from and self.migrate_to
        ), "TestCase '{}' must define migrate_from and migrate_to properties".format(
            type(self).__name__
        )
        self.migrate_from = [(self.app, self.migrate_from)]
        self.migrate_to = [(self.app, self.migrate_to)]
        executor = MigrationExecutor(connection)
        old_apps = executor.loader.project_state(self.migrate_from).apps

        # Reverse to the original migration
        executor.migrate(self.migrate_from)

        if self.migrate_fixtures:
            self.load_fixtures(self.migrate_fixtures, apps=old_apps)

        self.setUpBeforeMigration(old_apps)

        # Run the migration to test
        executor = MigrationExecutor(connection)
        executor.loader.build_graph()  # reload.
        executor.migrate(self.migrate_to)

        self.apps = executor.loader.project_state(self.migrate_to).apps

    def setUp(self):
        self.executor = MigrationExecutor(connection)

    def handle(self, *args, **options):
        changed = set()

        self.stdout.write("Checking...")
        for db in settings.DATABASES.keys():
            try:
                executor = MigrationExecutor(connections[db])
            except OperationalError:
                sys.exit("Unable to check migrations: cannot connect to database\n")

            autodetector = MigrationAutodetector(
                executor.loader.project_state(),
                ProjectState.from_apps(apps),
            )
            changed.update(autodetector.changes(graph=executor.loader.graph).keys())

        changed -= set(options['ignore'])

        if changed:
            sys.exit(
                "Apps with model changes but no corresponding migration file: %(changed)s\n" % {
                    'changed': list(changed)
                })
        else:
            sys.stdout.write("All migration files present\n")

    def handle(self, *args, **options):

        self.verbosity = options.get('verbosity')
        self.interactive = options.get('interactive')

        # Import the 'management' module within each installed app, to register
        # dispatcher events.
        for app_config in apps.get_app_configs():
            if module_has_submodule(app_config.module, "management"):
                import_module('.management', app_config.name)

        # Get the database we're operating from
        db = options.get('database')
        connection = connections[db]

        # If they asked for a migration listing, quit main execution flow and show it
        if options.get("list", False):
            warnings.warn(
                "The 'migrate --list' command is deprecated. Use 'showmigrations' instead.",
                RemovedInDjango110Warning, stacklevel=2)
            self.stdout.ending = None  # Remove when #21429 is fixed
            return call_command(
                'showmigrations',
                '--list',
                app_labels=[options['app_label']] if options['app_label'] else None,
                database=db,
                no_color=options.get('no_color'),
                settings=options.get('settings'),
                stdout=self.stdout,
                traceback=options.get('traceback'),
                verbosity=self.verbosity,
            )

        # Hook for backends needing any database preparation
        connection.prepare_database()
        # Work out which apps have migrations and which do not
        executor = MigrationExecutor(connection, self.migration_progress_callback)

        # Before anything else, see if there's conflicting apps and drop out
        # hard if there are any
        conflicts = executor.loader.detect_conflicts()
        if conflicts:
            name_str = "; ".join(
                "%s in %s" % (", ".join(names), app)
                for app, names in conflicts.items()
            )
            raise CommandError(
                "Conflicting migrations detected; multiple leaf nodes in the "
                "migration graph: (%s).\nTo fix them run "
                "'python manage.py makemigrations --merge'" % name_str
            )

        # If they supplied command line arguments, work out what they mean.
        target_app_labels_only = True
        if options['app_label'] and options['migration_name']:
            app_label, migration_name = options['app_label'], options['migration_name']
            if app_label not in executor.loader.migrated_apps:
                raise CommandError(
                    "App '%s' does not have migrations." % app_label
                )
            if migration_name == "zero":
                targets = [(app_label, None)]
            else:
                try:
                    migration = executor.loader.get_migration_by_prefix(app_label, migration_name)
                except AmbiguityError:
                    raise CommandError(
                        "More than one migration matches '%s' in app '%s'. "
                        "Please be more specific." %
                        (migration_name, app_label)
                    )
                except KeyError:
                    raise CommandError("Cannot find a migration matching '%s' from app '%s'." % (
                        migration_name, app_label))
                targets = [(app_label, migration.name)]
            target_app_labels_only = False
        elif options['app_label']:
            app_label = options['app_label']
            if app_label not in executor.loader.migrated_apps:
                raise CommandError(
                    "App '%s' does not have migrations." % app_label
                )
            targets = [key for key in executor.loader.graph.leaf_nodes() if key[0] == app_label]
        else:
            targets = executor.loader.graph.leaf_nodes()

        plan = executor.migration_plan(targets)
        run_syncdb = options.get('run_syncdb') and executor.loader.unmigrated_apps

        # Print some useful info
        if self.verbosity >= 1:
            self.stdout.write(self.style.MIGRATE_HEADING("Operations to perform:"))
            if run_syncdb:
                self.stdout.write(
                    self.style.MIGRATE_LABEL("  Synchronize unmigrated apps: ") +
                    (", ".join(executor.loader.unmigrated_apps))
                )
            if target_app_labels_only:
                self.stdout.write(
                    self.style.MIGRATE_LABEL("  Apply all migrations: ") +
                    (", ".join(set(a for a, n in targets)) or "(none)")
                )
            else:
                if targets[0][1] is None:
                    self.stdout.write(self.style.MIGRATE_LABEL(
                        "  Unapply all migrations: ") + "%s" % (targets[0][0], )
                    )
                else:
                    self.stdout.write(self.style.MIGRATE_LABEL(
                        "  Target specific migration: ") + "%s, from %s"
                        % (targets[0][1], targets[0][0])
                    )

        emit_pre_migrate_signal(self.verbosity, self.interactive, connection.alias)

        # Run the syncdb phase.
        if run_syncdb:
            if self.verbosity >= 1:
                self.stdout.write(self.style.MIGRATE_HEADING("Synchronizing apps without migrations:"))
            self.sync_apps(connection, executor.loader.unmigrated_apps)

        # Migrate!
        if self.verbosity >= 1:
            self.stdout.write(self.style.MIGRATE_HEADING("Running migrations:"))
        if not plan:
            executor.check_replacements()
            if self.verbosity >= 1:
                self.stdout.write("  No migrations to apply.")
                # If there's changes that aren't in migrations yet, tell them how to fix it.
                autodetector = MigrationAutodetector(
                    executor.loader.project_state(),
                    ProjectState.from_apps(apps),
                )
                changes = autodetector.changes(graph=executor.loader.graph)
                if changes:
                    self.stdout.write(self.style.NOTICE(
                        "  Your models have changes that are not yet reflected "
                        "in a migration, and so won't be applied."
                    ))
                    self.stdout.write(self.style.NOTICE(
                        "  Run 'manage.py makemigrations' to make new "
                        "migrations, and then re-run 'manage.py migrate' to "
                        "apply them."
                    ))
        else:
            fake = options.get("fake")
            fake_initial = options.get("fake_initial")
            executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)

        # Send the post_migrate signal, so individual apps can do whatever they need
        # to do at this point.
        emit_post_migrate_signal(self.verbosity, self.interactive, connection.alias)

    def check_migrations(self):
        """
        Checks to see if the set of migrations on disk matches the
        migrations in the database. Prints a warning if they don't match.
        """
        try:
            executor = MigrationExecutor(connections[DEFAULT_DB_ALIAS])
        except ImproperlyConfigured:
            # No databases are configured (or the dummy one)
            return
        except MigrationSchemaMissing:
            self.stdout.write(self.style.NOTICE(
                "\nNot checking migrations as it is not possible to access/create the django_migrations table."
            ))
            return

        plan = executor.migration_plan(executor.loader.graph.leaf_nodes())
        if plan:
            self.stdout.write(self.style.NOTICE(
                "\nYou have unapplied migrations; your app may not work properly until they are applied."
            ))
            self.stdout.write(self.style.NOTICE("Run 'python manage.py migrate' to apply them.\n"))

    def handle(self, *args, **options):
        # Get the database we're operating from
        connection = connections[options['database']]

        # Load up an executor to get all the migration data
        executor = MigrationExecutor(connection)

        # Resolve command-line arguments into a migration
        app_label, migration_name = options['app_label'], options['migration_name']
        if app_label not in executor.loader.migrated_apps:
            raise CommandError("App '%s' does not have migrations" % app_label)
        try:
            migration = executor.loader.get_migration_by_prefix(app_label, migration_name)
        except AmbiguityError:
            raise CommandError("More than one migration matches '%s' in app '%s'. Please be more specific." % (
                migration_name, app_label))
        except KeyError:
            raise CommandError("Cannot find a migration matching '%s' from app '%s'. Is it in INSTALLED_APPS?" % (
                migration_name, app_label))
        targets = [(app_label, migration.name)]

        # Make a plan that represents just the requested migrations and show SQL
        # for it
        plan = [(executor.loader.graph.nodes[targets[0]], options['backwards'])]
        sql_statements = executor.collect_sql(plan)
        return '\n'.join(sql_statements)

    def setUp(self):
        super(MigrationTestCase, self).setUp()
        self.executor = MigrationExecutor(connection)
        self.executor.migrate(self.migrate_origin)

def check_migrations():
	from django.db.migrations.autodetector import MigrationAutodetector
	from django.db.migrations.executor import MigrationExecutor
	from django.db.migrations.state import ProjectState

	changed = set()

	print("Checking {} migrations...".format(APP_NAME))
	for db in settings.DATABASES.keys():
		try:
			executor = MigrationExecutor(connections[db])
		except OperationalError as e:
			sys.exit(
				"Unable to check migrations due to database: {}".format(e)
			)

		autodetector = MigrationAutodetector(
			executor.loader.project_state(),
			ProjectState.from_apps(apps),
		)

		changed.update(
			autodetector.changes(graph=executor.loader.graph).keys()
		)

	if changed and APP_NAME in changed:
		sys.exit(
			"A migration file is missing. Please run "
			"`python makemigrations.py` to generate it."
		)
	else:
		print("All migration files present.")

    def setUp(self):
        astert (
            self.migrate_from and self.migrate_to
        ), "TestCase '{}' must define migrate_from and migrate_to properties".format(
            type(self).__name__
        )

        migrate_from = [(self.app, self.migrate_from)]
        migrate_to = [(self.app, self.migrate_to)]
        executor = MigrationExecutor(connection)
        old_apps = executor.loader.project_state(migrate_from).apps

        # Reverse to the original migration
        executor.migrate(migrate_from)

        self.setUpBeforeMigration(old_apps)

        # Run the migration to test
        executor = MigrationExecutor(connection)
        executor.loader.build_graph()  # reload.
        executor.migrate(migrate_to)

        self.apps = executor.loader.project_state(migrate_to).apps

    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations"})
    def test_run(self):
        """
        Tests running a simple set of migrations.
        """
        executor = MigrationExecutor(connection)
        # Let's look at the plan first and make sure it's up to scratch
        plan = executor.migration_plan([("migrations", "0002_second")])
        self.astertEqual(
            plan,
            [
                (executor.loader.graph.nodes["migrations", "0001_initial"], False),
                (executor.loader.graph.nodes["migrations", "0002_second"], False),
            ],
        )
        # Were the tables there before?
        self.astertTableNotExists("migrations_author")
        self.astertTableNotExists("migrations_book")
        # Alright, let's try running it
        executor.migrate([("migrations", "0002_second")])
        # Are the tables there now?
        self.astertTableExists("migrations_author")
        self.astertTableExists("migrations_book")
        # Rebuild the graph to reflect the new DB state
        executor.loader.build_graph()
        # Alright, let's undo what we did
        plan = executor.migration_plan([("migrations", None)])
        self.astertEqual(
            plan,
            [
                (executor.loader.graph.nodes["migrations", "0002_second"], True),
                (executor.loader.graph.nodes["migrations", "0001_initial"], True),
            ],
        )
        executor.migrate([("migrations", None)])
        # Are the tables gone?
        self.astertTableNotExists("migrations_author")
        self.astertTableNotExists("migrations_book")

    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_squashed"})
    def test_run_with_squashed(self):
        """
        Tests running a squashed migration from zero (should ignore what it replaces)
        """
        executor = MigrationExecutor(connection)
        # Check our leaf node is the squashed one
        leaves = [key for key in executor.loader.graph.leaf_nodes() if key[0] == "migrations"]
        self.astertEqual(leaves, [("migrations", "0001_squashed_0002")])
        # Check the plan
        plan = executor.migration_plan([("migrations", "0001_squashed_0002")])
        self.astertEqual(
            plan,
            [
                (executor.loader.graph.nodes["migrations", "0001_squashed_0002"], False),
            ],
        )
        # Were the tables there before?
        self.astertTableNotExists("migrations_author")
        self.astertTableNotExists("migrations_book")
        # Alright, let's try running it
        executor.migrate([("migrations", "0001_squashed_0002")])
        # Are the tables there now?
        self.astertTableExists("migrations_author")
        self.astertTableExists("migrations_book")
        # Rebuild the graph to reflect the new DB state
        executor.loader.build_graph()
        # Alright, let's undo what we did. Should also just use squashed.
        plan = executor.migration_plan([("migrations", None)])
        self.astertEqual(
            plan,
            [
                (executor.loader.graph.nodes["migrations", "0001_squashed_0002"], True),
            ],
        )
        executor.migrate([("migrations", None)])
        # Are the tables gone?
        self.astertTableNotExists("migrations_author")
        self.astertTableNotExists("migrations_book")

    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_atomic_operation"})
    def test_atomic_operation_in_non_atomic_migration(self):
        """
        An atomic operation is properly rolled back inside a non-atomic
        migration.
        """
        executor = MigrationExecutor(connection)
        with self.astertRaisesMessage(RuntimeError, "Abort migration"):
            executor.migrate([("migrations", "0001_initial")])
        migrations_apps = executor.loader.project_state(("migrations", "0001_initial")).apps
        Editor = migrations_apps.get_model("migrations", "Editor")
        self.astertFalse(Editor.objects.exists())
        # Record previous migration as successful.
        executor.migrate([("migrations", "0001_initial")], fake=True)
        # Rebuild the graph to reflect the new DB state.
        executor.loader.build_graph()
        # Migrating backwards is also atomic.
        with self.astertRaisesMessage(RuntimeError, "Abort migration"):
            executor.migrate([("migrations", None)])
        self.astertFalse(Editor.objects.exists())

    @override_settings(MIGRATION_MODULES={
        "migrations": "migrations.test_migrations",
        "migrations2": "migrations2.test_migrations_2",
    })
    def test_empty_plan(self):
        """
        Re-planning a full migration of a fully-migrated set doesn't
        perform spurious unmigrations and remigrations.

        There was previously a bug where the executor just always performed the
        backwards plan for applied migrations - which even for the most recent
        migration in an app, might include other, dependent apps, and these
        were being unmigrated.
        """
        # Make the initial plan, check it
        executor = MigrationExecutor(connection)
        plan = executor.migration_plan([
            ("migrations", "0002_second"),
            ("migrations2", "0001_initial"),
        ])
        self.astertEqual(
            plan,
            [
                (executor.loader.graph.nodes["migrations", "0001_initial"], False),
                (executor.loader.graph.nodes["migrations", "0002_second"], False),
                (executor.loader.graph.nodes["migrations2", "0001_initial"], False),
            ],
        )
        # Fake-apply all migrations
        executor.migrate([
            ("migrations", "0002_second"),
            ("migrations2", "0001_initial")
        ], fake=True)
        # Rebuild the graph to reflect the new DB state
        executor.loader.build_graph()
        # Now plan a second time and make sure it's empty
        plan = executor.migration_plan([
            ("migrations", "0002_second"),
            ("migrations2", "0001_initial"),
        ])
        self.astertEqual(plan, [])
        # The resulting state should include applied migrations.
        state = executor.migrate([
            ("migrations", "0002_second"),
            ("migrations2", "0001_initial"),
        ])
        self.astertIn(('migrations', 'book'), state.models)
        self.astertIn(('migrations', 'author'), state.models)
        self.astertIn(('migrations2', 'otherauthor'), state.models)
        # Erase all the fake records
        executor.recorder.record_unapplied("migrations2", "0001_initial")
        executor.recorder.record_unapplied("migrations", "0002_second")
        executor.recorder.record_unapplied("migrations", "0001_initial")

    @override_settings(MIGRATION_MODULES={
        "migrations": "migrations.test_migrations",
        "migrations2": "migrations2.test_migrations_2_no_deps",
    })
    def test_mixed_plan_not_supported(self):
        """
        Although the MigrationExecutor interfaces allows for mixed migration
        plans (combined forwards and backwards migrations) this is not
        supported.
        """
        # Prepare for mixed plan
        executor = MigrationExecutor(connection)
        plan = executor.migration_plan([("migrations", "0002_second")])
        self.astertEqual(
            plan,
            [
                (executor.loader.graph.nodes["migrations", "0001_initial"], False),
                (executor.loader.graph.nodes["migrations", "0002_second"], False),
            ],
        )
        executor.migrate(None, plan)
        # Rebuild the graph to reflect the new DB state
        executor.loader.build_graph()
        self.astertIn(('migrations', '0001_initial'), executor.loader.applied_migrations)
        self.astertIn(('migrations', '0002_second'), executor.loader.applied_migrations)
        self.astertNotIn(('migrations2', '0001_initial'), executor.loader.applied_migrations)

        # Generate mixed plan
        plan = executor.migration_plan([
            ("migrations", None),
            ("migrations2", "0001_initial"),
        ])
        msg = (
            'Migration plans with both forwards and backwards migrations are '
            'not supported. Please split your migration process into separate '
            'plans of only forwards OR backwards migrations.'
        )
        with self.astertRaisesMessage(InvalidMigrationPlan, msg) as cm:
            executor.migrate(None, plan)
        self.astertEqual(
            cm.exception.args[1],
            [
                (executor.loader.graph.nodes["migrations", "0002_second"], True),
                (executor.loader.graph.nodes["migrations", "0001_initial"], True),
                (executor.loader.graph.nodes["migrations2", "0001_initial"], False),
            ],
        )
        # Rebuild the graph to reflect the new DB state
        executor.loader.build_graph()
        executor.migrate([
            ("migrations", None),
            ("migrations2", None),
        ])
        # Are the tables gone?
        self.astertTableNotExists("migrations_author")
        self.astertTableNotExists("migrations_book")
        self.astertTableNotExists("migrations2_otherauthor")

    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations"})
    def test_soft_apply(self):
        """
        Tests detection of initial migrations already having been applied.
        """
        state = {"faked": None}

        def fake_storer(phase, migration=None, fake=None):
            state["faked"] = fake
        executor = MigrationExecutor(connection, progress_callback=fake_storer)
        # Were the tables there before?
        self.astertTableNotExists("migrations_author")
        self.astertTableNotExists("migrations_tribble")
        # Run it normally
        self.astertEqual(
            executor.migration_plan([("migrations", "0001_initial")]),
            [
                (executor.loader.graph.nodes["migrations", "0001_initial"], False),
            ],
        )
        executor.migrate([("migrations", "0001_initial")])
        # Are the tables there now?
        self.astertTableExists("migrations_author")
        self.astertTableExists("migrations_tribble")
        # We shouldn't have faked that one
        self.astertIs(state["faked"], False)
        # Rebuild the graph to reflect the new DB state
        executor.loader.build_graph()
        # Fake-reverse that
        executor.migrate([("migrations", None)], fake=True)
        # Are the tables still there?
        self.astertTableExists("migrations_author")
        self.astertTableExists("migrations_tribble")
        # Make sure that was faked
        self.astertIs(state["faked"], True)
        # Finally, migrate forwards; this should fake-apply our initial migration
        executor.loader.build_graph()
        self.astertEqual(
            executor.migration_plan([("migrations", "0001_initial")]),
            [
                (executor.loader.graph.nodes["migrations", "0001_initial"], False),
            ],
        )
        # Applying the migration should raise a database level error
        # because we haven't given the --fake-initial option
        with self.astertRaises(DatabaseError):
            executor.migrate([("migrations", "0001_initial")])
        # Reset the faked state
        state = {"faked": None}
        # Allow faking of initial CreateModel operations
        executor.migrate([("migrations", "0001_initial")], fake_initial=True)
        self.astertIs(state["faked"], True)
        # And migrate back to clean up the database
        executor.loader.build_graph()
        executor.migrate([("migrations", None)])
        self.astertTableNotExists("migrations_author")
        self.astertTableNotExists("migrations_tribble")

    @override_settings(
        MIGRATION_MODULES={
            "migrations": "migrations.test_migrations_custom_user",
            "django.contrib.auth": "django.contrib.auth.migrations",
        },
        AUTH_USER_MODEL="migrations.Author",
    )
    def test_custom_user(self):
        """
        Regression test for #22325 - references to a custom user model defined in the
        same app are not resolved correctly.
        """
        executor = MigrationExecutor(connection)
        self.astertTableNotExists("migrations_author")
        self.astertTableNotExists("migrations_tribble")
        # Migrate forwards
        executor.migrate([("migrations", "0001_initial")])
        self.astertTableExists("migrations_author")
        self.astertTableExists("migrations_tribble")
        # Make sure the soft-application detection works (#23093)
        # Change table_names to not return auth_user during this as
        # it wouldn't be there in a normal run, and ensure migrations.Author
        # exists in the global app registry temporarily.
        old_table_names = connection.introspection.table_names
        connection.introspection.table_names = lambda c: [x for x in old_table_names(c) if x != "auth_user"]
        migrations_apps = executor.loader.project_state(("migrations", "0001_initial")).apps
        global_apps.get_app_config("migrations").models["author"] = migrations_apps.get_model("migrations", "author")
        try:
            migration = executor.loader.get_migration("auth", "0001_initial")
            self.astertIs(executor.detect_soft_applied(None, migration)[0], True)
        finally:
            connection.introspection.table_names = old_table_names
            del global_apps.get_app_config("migrations").models["author"]
        # And migrate back to clean up the database
        executor.loader.build_graph()
        executor.migrate([("migrations", None)])
        self.astertTableNotExists("migrations_author")
        self.astertTableNotExists("migrations_tribble")

    @override_settings(
        MIGRATION_MODULES={
            "migrations": "migrations.test_add_many_to_many_field_initial",
        },
    )
    def test_detect_soft_applied_add_field_manytomanyfield(self):
        """
        executor.detect_soft_applied() detects ManyToManyField tables from an
        AddField operation. This checks the case of AddField in a migration
        with other operations (0001) and the case of AddField in its own
        migration (0002).
        """
        tables = [
            # from 0001
            "migrations_project",
            "migrations_task",
            "migrations_project_tasks",
            # from 0002
            "migrations_task_projects",
        ]
        executor = MigrationExecutor(connection)
        # Create the tables for 0001 but make it look like the migration hasn't
        # been applied.
        executor.migrate([("migrations", "0001_initial")])
        executor.migrate([("migrations", None)], fake=True)
        for table in tables[:3]:
            self.astertTableExists(table)
        # Table detection sees 0001 is applied but not 0002.
        migration = executor.loader.get_migration("migrations", "0001_initial")
        self.astertIs(executor.detect_soft_applied(None, migration)[0], True)
        migration = executor.loader.get_migration("migrations", "0002_initial")
        self.astertIs(executor.detect_soft_applied(None, migration)[0], False)

        # Create the tables for both migrations but make it look like neither
        # has been applied.
        executor.loader.build_graph()
        executor.migrate([("migrations", "0001_initial")], fake=True)
        executor.migrate([("migrations", "0002_initial")])
        executor.loader.build_graph()
        executor.migrate([("migrations", None)], fake=True)
        # Table detection sees 0002 is applied.
        migration = executor.loader.get_migration("migrations", "0002_initial")
        self.astertIs(executor.detect_soft_applied(None, migration)[0], True)

        # Leave the tables for 0001 except the many-to-many table. That missing
        # table should cause detect_soft_applied() to return False.
        with connection.schema_editor() as editor:
            for table in tables[2:]:
                editor.execute(editor.sql_delete_table % {"table": table})
        migration = executor.loader.get_migration("migrations", "0001_initial")
        self.astertIs(executor.detect_soft_applied(None, migration)[0], False)

        # Cleanup by removing the remaining tables.
        with connection.schema_editor() as editor:
            for table in tables[:2]:
                editor.execute(editor.sql_delete_table % {"table": table})
        for table in tables:
            self.astertTableNotExists(table)

    @override_settings(
        INSTALLED_APPS=[
            "migrations.migrations_test_apps.lookuperror_a",
            "migrations.migrations_test_apps.lookuperror_b",
            "migrations.migrations_test_apps.lookuperror_c"
        ]
    )
    def test_unrelated_model_lookups_forwards(self):
        """
        #24123 - All models of apps already applied which are
        unrelated to the first app being applied are part of the initial model
        state.
        """
        try:
            executor = MigrationExecutor(connection)
            self.astertTableNotExists("lookuperror_a_a1")
            self.astertTableNotExists("lookuperror_b_b1")
            self.astertTableNotExists("lookuperror_c_c1")
            executor.migrate([("lookuperror_b", "0003_b3")])
            self.astertTableExists("lookuperror_b_b3")
            # Rebuild the graph to reflect the new DB state
            executor.loader.build_graph()

            # Migrate forwards -- This led to a lookup LookupErrors because
            # lookuperror_b.B2 is already applied
            executor.migrate([
                ("lookuperror_a", "0004_a4"),
                ("lookuperror_c", "0003_c3"),
            ])
            self.astertTableExists("lookuperror_a_a4")
            self.astertTableExists("lookuperror_c_c3")

            # Rebuild the graph to reflect the new DB state
            executor.loader.build_graph()
        finally:
            # Cleanup
            executor.migrate([
                ("lookuperror_a", None),
                ("lookuperror_b", None),
                ("lookuperror_c", None),
            ])
            self.astertTableNotExists("lookuperror_a_a1")
            self.astertTableNotExists("lookuperror_b_b1")
            self.astertTableNotExists("lookuperror_c_c1")

    @override_settings(
        INSTALLED_APPS=[
            "migrations.migrations_test_apps.lookuperror_a",
            "migrations.migrations_test_apps.lookuperror_b",
            "migrations.migrations_test_apps.lookuperror_c"
        ]
    )
    def test_unrelated_model_lookups_backwards(self):
        """
        #24123 - All models of apps being unapplied which are
        unrelated to the first app being unapplied are part of the initial
        model state.
        """
        try:
            executor = MigrationExecutor(connection)
            self.astertTableNotExists("lookuperror_a_a1")
            self.astertTableNotExists("lookuperror_b_b1")
            self.astertTableNotExists("lookuperror_c_c1")
            executor.migrate([
                ("lookuperror_a", "0004_a4"),
                ("lookuperror_b", "0003_b3"),
                ("lookuperror_c", "0003_c3"),
            ])
            self.astertTableExists("lookuperror_b_b3")
            self.astertTableExists("lookuperror_a_a4")
            self.astertTableExists("lookuperror_c_c3")
            # Rebuild the graph to reflect the new DB state
            executor.loader.build_graph()

            # Migrate backwards -- This led to a lookup LookupErrors because
            # lookuperror_b.B2 is not in the initial state (unrelated to app c)
            executor.migrate([("lookuperror_a", None)])

            # Rebuild the graph to reflect the new DB state
            executor.loader.build_graph()
        finally:
            # Cleanup
            executor.migrate([
                ("lookuperror_b", None),
                ("lookuperror_c", None)
            ])
            self.astertTableNotExists("lookuperror_a_a1")
            self.astertTableNotExists("lookuperror_b_b1")
            self.astertTableNotExists("lookuperror_c_c1")

    @override_settings(
        INSTALLED_APPS=[
            'migrations.migrations_test_apps.mutate_state_a',
            'migrations.migrations_test_apps.mutate_state_b',
        ]
    )
    def test_unrelated_applied_migrations_mutate_state(self):
        """
        #26647 - Unrelated applied migrations should be part of the final
        state in both directions.
        """
        executor = MigrationExecutor(connection)
        executor.migrate([
            ('mutate_state_b', '0002_add_field'),
        ])
        # Migrate forward.
        executor.loader.build_graph()
        state = executor.migrate([
            ('mutate_state_a', '0001_initial'),
        ])
        self.astertIn('added', dict(state.models['mutate_state_b', 'b'].fields))
        executor.loader.build_graph()
        # Migrate backward.
        state = executor.migrate([
            ('mutate_state_a', None),
        ])
        self.astertIn('added', dict(state.models['mutate_state_b', 'b'].fields))
        executor.migrate([
            ('mutate_state_b', None),
        ])

    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations"})
    def test_process_callback(self):
        """
        #24129 - Tests callback process
        """
        call_args_list = []

        def callback(*args):
            call_args_list.append(args)

        executor = MigrationExecutor(connection, progress_callback=callback)
        # Were the tables there before?
        self.astertTableNotExists("migrations_author")
        self.astertTableNotExists("migrations_tribble")
        executor.migrate([
            ("migrations", "0001_initial"),
            ("migrations", "0002_second"),
        ])
        # Rebuild the graph to reflect the new DB state
        executor.loader.build_graph()

        executor.migrate([
            ("migrations", None),
            ("migrations", None),
        ])
        self.astertTableNotExists("migrations_author")
        self.astertTableNotExists("migrations_tribble")

        migrations = executor.loader.graph.nodes
        expected = [
            ("render_start",),
            ("render_success",),
            ("apply_start", migrations['migrations', '0001_initial'], False),
            ("apply_success", migrations['migrations', '0001_initial'], False),
            ("apply_start", migrations['migrations', '0002_second'], False),
            ("apply_success", migrations['migrations', '0002_second'], False),
            ("render_start",),
            ("render_success",),
            ("unapply_start", migrations['migrations', '0002_second'], False),
            ("unapply_success", migrations['migrations', '0002_second'], False),
            ("unapply_start", migrations['migrations', '0001_initial'], False),
            ("unapply_success", migrations['migrations', '0001_initial'], False),
        ]
        self.astertEqual(call_args_list, expected)

    @override_settings(
        INSTALLED_APPS=[
            "migrations.migrations_test_apps.alter_fk.author_app",
            "migrations.migrations_test_apps.alter_fk.book_app",
        ]
    )
    def test_alter_id_type_with_fk(self):
        try:
            executor = MigrationExecutor(connection)
            self.astertTableNotExists("author_app_author")
            self.astertTableNotExists("book_app_book")
            # Apply initial migrations
            executor.migrate([
                ("author_app", "0001_initial"),
                ("book_app", "0001_initial"),
            ])
            self.astertTableExists("author_app_author")
            self.astertTableExists("book_app_book")
            # Rebuild the graph to reflect the new DB state
            executor.loader.build_graph()

            # Apply PK type alteration
            executor.migrate([("author_app", "0002_alter_id")])

            # Rebuild the graph to reflect the new DB state
            executor.loader.build_graph()
        finally:
            # We can't simply unapply the migrations here because there is no
            # implicit cast from VARCHAR to INT on the database level.
            with connection.schema_editor() as editor:
                editor.execute(editor.sql_delete_table % {"table": "book_app_book"})
                editor.execute(editor.sql_delete_table % {"table": "author_app_author"})
            self.astertTableNotExists("author_app_author")
            self.astertTableNotExists("book_app_book")
            executor.migrate([("author_app", None)], fake=True)

    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_squashed"})
    def test_apply_all_replaced_marks_replacement_as_applied(self):
        """
        Applying all replaced migrations marks replacement as applied (#24628).
        """
        recorder = MigrationRecorder(connection)
        # Place the database in a state where the replaced migrations are
        # partially applied: 0001 is applied, 0002 is not.
        recorder.record_applied("migrations", "0001_initial")
        executor = MigrationExecutor(connection)
        # Use fake because we don't actually have the first migration
        # applied, so the second will fail. And there's no need to actually
        # create/modify tables here, we're just testing the
        # MigrationRecord, which works the same with or without fake.
        executor.migrate([("migrations", "0002_second")], fake=True)

        # Because we've now applied 0001 and 0002 both, their squashed
        # replacement should be marked as applied.
        self.astertIn(
            ("migrations", "0001_squashed_0002"),
            recorder.applied_migrations(),
        )

    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_squashed"})
    def test_migrate_marks_replacement_applied_even_if_it_did_nothing(self):
        """
        A new squash migration will be marked as applied even if all its
        replaced migrations were previously already applied (#24628).
        """
        recorder = MigrationRecorder(connection)
        # Record all replaced migrations as applied
        recorder.record_applied("migrations", "0001_initial")
        recorder.record_applied("migrations", "0002_second")
        executor = MigrationExecutor(connection)
        executor.migrate([("migrations", "0001_squashed_0002")])

        # Because 0001 and 0002 are both applied, even though this migrate run
        # didn't apply anything new, their squashed replacement should be
        # marked as applied.
        self.astertIn(
            ("migrations", "0001_squashed_0002"),
            recorder.applied_migrations(),
        )

    def test_minimize_rollbacks(self):
        """
        Minimize unnecessary rollbacks in connected apps.

        When you say "./manage.py migrate appA 0001", rather than migrating to
        just after appA-0001 in the linearized migration plan (which could roll
        back migrations in other apps that depend on appA 0001, but don't need
        to be rolled back since we're not rolling back appA 0001), we migrate
        to just before appA-0002.
        """
        a1_impl = FakeMigration('a1')
        a1 = ('a', '1')
        a2_impl = FakeMigration('a2')
        a2 = ('a', '2')
        b1_impl = FakeMigration('b1')
        b1 = ('b', '1')
        graph = MigrationGraph()
        graph.add_node(a1, a1_impl)
        graph.add_node(a2, a2_impl)
        graph.add_node(b1, b1_impl)
        graph.add_dependency(None, b1, a1)
        graph.add_dependency(None, a2, a1)

        executor = MigrationExecutor(None)
        executor.loader = FakeLoader(graph, {a1, b1, a2})

        plan = executor.migration_plan({a1})

        self.astertEqual(plan, [(a2_impl, True)])

    def test_minimize_rollbacks_branchy(self):
        r"""
        Minimize rollbacks when target has multiple in-app children.

        a: 1 <---- 3 <--\
              \ \- 2 <--- 4
               \       \
        b:      \- 1 <--- 2
        """
        a1_impl = FakeMigration('a1')
        a1 = ('a', '1')
        a2_impl = FakeMigration('a2')
        a2 = ('a', '2')
        a3_impl = FakeMigration('a3')
        a3 = ('a', '3')
        a4_impl = FakeMigration('a4')
        a4 = ('a', '4')
        b1_impl = FakeMigration('b1')
        b1 = ('b', '1')
        b2_impl = FakeMigration('b2')
        b2 = ('b', '2')
        graph = MigrationGraph()
        graph.add_node(a1, a1_impl)
        graph.add_node(a2, a2_impl)
        graph.add_node(a3, a3_impl)
        graph.add_node(a4, a4_impl)
        graph.add_node(b1, b1_impl)
        graph.add_node(b2, b2_impl)
        graph.add_dependency(None, a2, a1)
        graph.add_dependency(None, a3, a1)
        graph.add_dependency(None, a4, a2)
        graph.add_dependency(None, a4, a3)
        graph.add_dependency(None, b2, b1)
        graph.add_dependency(None, b1, a1)
        graph.add_dependency(None, b2, a2)

        executor = MigrationExecutor(None)
        executor.loader = FakeLoader(graph, {a1, b1, a2, b2, a3, a4})

        plan = executor.migration_plan({a1})

        should_be_rolled_back = [b2_impl, a4_impl, a2_impl, a3_impl]
        exp = [(m, True) for m in should_be_rolled_back]
        self.astertEqual(plan, exp)

    def test_backwards_nothing_to_do(self):
        r"""
        If the current state satisfies the given target, do nothing.

        a: 1 <--- 2
        b:    \- 1
        c:     \- 1

        If a1 is applied already and a2 is not, and we're asked to migrate to
        a1, don't apply or unapply b1 or c1, regardless of their current state.
        """
        a1_impl = FakeMigration('a1')
        a1 = ('a', '1')
        a2_impl = FakeMigration('a2')
        a2 = ('a', '2')
        b1_impl = FakeMigration('b1')
        b1 = ('b', '1')
        c1_impl = FakeMigration('c1')
        c1 = ('c', '1')
        graph = MigrationGraph()
        graph.add_node(a1, a1_impl)
        graph.add_node(a2, a2_impl)
        graph.add_node(b1, b1_impl)
        graph.add_node(c1, c1_impl)
        graph.add_dependency(None, a2, a1)
        graph.add_dependency(None, b1, a1)
        graph.add_dependency(None, c1, a1)

        executor = MigrationExecutor(None)
        executor.loader = FakeLoader(graph, {a1, b1})

        plan = executor.migration_plan({a1})

        self.astertEqual(plan, [])

def get_fake_model(fields=None, model_base=models.Model, options=None):
    fields = fields if fields else {}
    options = options if options else {}
    """Create fake model to use during unit tests."""

    model = define_fake_model(fields, model_base, options)

    clast TestProject:
        def clone(self, *_args, **_kwargs):
            return self

    clast TestMigration(migrations.Migration):
        operations = [HStoreExtension()]

    with connection.schema_editor() as schema_editor:
        migration_executor = MigrationExecutor(schema_editor.connection)
        migration_executor.apply_migration(
            TestProject(), TestMigration("caluma_extra", "core")
        )

        schema_editor.create_model(model)

    return model

def test_migrate_to_flat_answers(transactional_db):
    executor = MigrationExecutor(connection)
    app = "form"
    migrate_from = [(app, "0017_auto_20190619_1320")]
    migrate_to = [(app, "0019_remove_answer_value_docameent")]

    executor.migrate(migrate_from)
    old_apps = executor.loader.project_state(migrate_from).apps

    # Create some old data. Can't use factories here

    Docameent = old_apps.get_model(app, "Docameent")
    Form = old_apps.get_model(app, "Form")
    Answer = old_apps.get_model(app, "Answer")
    Question = old_apps.get_model(app, "Question")
    FormQuestion = old_apps.get_model(app, "FormQuestion")

    main_form = Form.objects.create(slug="main-form")
    sub_form = Form.objects.create(slug="sub-form")

    main_form_question = Question.objects.create(
        type="form", sub_form=sub_form, slug="main-form-question"
    )
    FormQuestion.objects.create(form=main_form, question=main_form_question)

    main_text_question = Question.objects.create(type="text", slug="main-text-question")
    FormQuestion.objects.create(form=main_form, question=main_text_question)

    sub_text_question = Question.objects.create(type="text", slug="sub_1_question_1")
    FormQuestion.objects.create(form=sub_form, question=sub_text_question)

    # we need to set a temporary family, because the signals are not available
    main_docameent = Docameent.objects.create(form=main_form, family=uuid4())
    # then we set the correct family
    main_docameent.family = main_docameent.pk
    main_docameent.save()

    sub_docameent = Docameent.objects.create(form=sub_form, family=main_docameent.pk)
    sub_answer = Answer.objects.create(
        value="lorem ipsum", question=sub_text_question, docameent=sub_docameent
    )
    Answer.objects.create(
        value_docameent=sub_docameent, question=main_form_question, docameent=main_docameent
    )

    text_answer = Answer.objects.create(
        value="dolor sit", question=main_text_question, docameent=main_docameent
    )

    astert not sub_answer.docameent == main_docameent
    astert text_answer.docameent == main_docameent

    # Migrate forwards.
    executor.loader.build_graph()  # reload.
    executor.migrate(migrate_to)
    new_apps = executor.loader.project_state(migrate_to).apps

    # Test the new data.
    Answer = new_apps.get_model(app, "Answer")

    sub_answer = Answer.objects.get(value="lorem ipsum")
    text_answer = Answer.objects.get(value="dolor sit")

    astert Answer.objects.filter(question__type="form").count() == 0
    astert sub_answer.docameent.pk == main_docameent.pk
    astert text_answer.docameent.pk == main_docameent.pk

def test_migrate_to_form_question_natural_key_forward(transactional_db):
    executor = MigrationExecutor(connection)
    app = "form"
    migrate_from = [(app, "0023_auto_20190729_1448")]
    migrate_to = [(app, "0024_auto_20190919_1244")]

    executor.migrate(migrate_from)
    old_apps = executor.loader.project_state(migrate_from).apps

    # Create some old data. Can't use factories here

    Form = old_apps.get_model(app, "Form")
    Question = old_apps.get_model(app, "Question")
    FormQuestion = old_apps.get_model(app, "FormQuestion")

    form_1 = Form.objects.create(slug="form-1")

    question_1 = Question.objects.create(type="text", slug="question-1")
    form_question = FormQuestion.objects.create(form=form_1, question=question_1)

    astert isinstance(form_question.pk, UUID)

    # Migrate forwards.
    executor.loader.build_graph()  # reload.
    executor.migrate(migrate_to)
    new_apps = executor.loader.project_state(migrate_to).apps

    # Test the new data.
    FormQuestion = new_apps.get_model(app, "FormQuestion")

    form_question = FormQuestion.objects.first()

    astert form_question.pk == "form-1.question-1"

def test_migrate_to_form_question_natural_key_reverse(transactional_db):
    executor = MigrationExecutor(connection)
    app = "form"
    migrate_from = [(app, "0024_auto_20190919_1244")]
    migrate_to = [(app, "0023_auto_20190729_1448")]

    executor.migrate(migrate_from)
    old_apps = executor.loader.project_state(migrate_from).apps

    # Create some old data. Can't use factories here

    Form = old_apps.get_model(app, "Form")
    Question = old_apps.get_model(app, "Question")
    FormQuestion = old_apps.get_model(app, "FormQuestion")

    form_1 = Form.objects.create(slug="form-1")

    question_1 = Question.objects.create(type="text", slug="question-1")
    FormQuestion.objects.create(form=form_1, question=question_1)

    # Migrate backwards.
    executor.loader.build_graph()  # reload.
    with pytest.raises(DataError):
        executor.migrate(migrate_to)

    @clastmethod
    def setUpTestData(cls):
        """
        Injects data into the test database prior to the migration we're trying to test.

        This clast methods reverts the test database back to the state of the last migration file
        prior to the migrations we want to test. It will then allow the user to inject data into the
        test database by calling the `setUpMigrationData` hook. After the data has been injected, it
        will apply the migrations we want to test and call the `setUpPostMigrationData` hook. The
        user can now test if the migration correctly migrated the injected test data.
        """
        if not cls.app:
            raise ValueError("The `app` attribute was not set.")

        if not cls.migration_prior or not cls.migration_target:
            raise ValueError("Both ` migration_prior` and `migration_target` need to be set.")

        cls.migrate_from = [(cls.app, cls.migration_prior)]
        cls.migrate_to = [(cls.app, cls.migration_target)]

        # Reverse to database state prior to the migrations we want to test
        executor = MigrationExecutor(connection)
        executor.migrate(cls.migrate_from)

        # Call the data injection hook with the current state of the project
        old_apps = executor.loader.project_state(cls.migrate_from).apps
        cls.setUpMigrationData(old_apps)

        # Run the migrations we want to test
        executor = MigrationExecutor(connection)
        executor.loader.build_graph()
        executor.migrate(cls.migrate_to)

        # Save the project state so we're able to work with the correct model states
        cls.apps = executor.loader.project_state(cls.migrate_to).apps

        # Call `setUpPostMigrationData` to potentially set up post migration data used in testing
        cls.setUpPostMigrationData(cls.apps)

    def check_migrations(self):
        """
        Print a warning if the set of migrations on disk don't match the
        migrations in the database.
        """
        from django.db.migrations.executor import MigrationExecutor
        try:
            executor = MigrationExecutor(connections[DEFAULT_DB_ALIAS])
        except ImproperlyConfigured:
            # No databases are configured (or the dummy one)
            return

        plan = executor.migration_plan(executor.loader.graph.leaf_nodes())
        if plan:
            apps_waiting_migration = sorted({migration.app_label for migration, backwards in plan})
            self.stdout.write(
                self.style.NOTICE(
                    "\nYou have %(unpplied_migration_count)s unapplied migration(s). "
                    "Your project may not work properly until you apply the "
                    "migrations for app(s): %(apps_waiting_migration)s." % {
                        "unpplied_migration_count": len(plan),
                        "apps_waiting_migration": ", ".join(apps_waiting_migration),
                    }
                )
            )
            self.stdout.write(self.style.NOTICE("Run 'python manage.py migrate' to apply them.\n"))

    @no_translations
    def handle(self, *args, **options):

        self.verbosity = options['verbosity']
        self.interactive = options['interactive']

        # Import the 'management' module within each installed app, to register
        # dispatcher events.
        for app_config in apps.get_app_configs():
            if module_has_submodule(app_config.module, "management"):
                import_module('.management', app_config.name)

        # Get the database we're operating from
        db = options['database']
        connection = connections[db]

        # Hook for backends needing any database preparation
        connection.prepare_database()
        # Work out which apps have migrations and which do not
        executor = MigrationExecutor(connection, self.migration_progress_callback)

        # Raise an error if any migrations are applied before their dependencies.
        executor.loader.check_consistent_history(connection)

        # Before anything else, see if there's conflicting apps and drop out
        # hard if there are any
        conflicts = executor.loader.detect_conflicts()
        if conflicts:
            name_str = "; ".join(
                "%s in %s" % (", ".join(names), app)
                for app, names in conflicts.items()
            )
            raise CommandError(
                "Conflicting migrations detected; multiple leaf nodes in the "
                "migration graph: (%s).\nTo fix them run "
                "'python manage.py makemigrations --merge'" % name_str
            )

        # If they supplied command line arguments, work out what they mean.
        target_app_labels_only = True
        if options['app_label'] and options['migration_name']:
            app_label, migration_name = options['app_label'], options['migration_name']
            if app_label not in executor.loader.migrated_apps:
                raise CommandError(
                    "App '%s' does not have migrations." % app_label
                )
            if migration_name == "zero":
                targets = [(app_label, None)]
            else:
                try:
                    migration = executor.loader.get_migration_by_prefix(app_label, migration_name)
                except AmbiguityError:
                    raise CommandError(
                        "More than one migration matches '%s' in app '%s'. "
                        "Please be more specific." %
                        (migration_name, app_label)
                    )
                except KeyError:
                    raise CommandError("Cannot find a migration matching '%s' from app '%s'." % (
                        migration_name, app_label))
                targets = [(app_label, migration.name)]
            target_app_labels_only = False
        elif options['app_label']:
            app_label = options['app_label']
            if app_label not in executor.loader.migrated_apps:
                raise CommandError(
                    "App '%s' does not have migrations." % app_label
                )
            targets = [key for key in executor.loader.graph.leaf_nodes() if key[0] == app_label]
        else:
            targets = executor.loader.graph.leaf_nodes()

        plan = executor.migration_plan(targets)
        run_syncdb = options['run_syncdb'] and executor.loader.unmigrated_apps

        # Print some useful info
        if self.verbosity >= 1:
            self.stdout.write(self.style.MIGRATE_HEADING("Operations to perform:"))
            if run_syncdb:
                self.stdout.write(
                    self.style.MIGRATE_LABEL("  Synchronize unmigrated apps: ") +
                    (", ".join(sorted(executor.loader.unmigrated_apps)))
                )
            if target_app_labels_only:
                self.stdout.write(
                    self.style.MIGRATE_LABEL("  Apply all migrations: ") +
                    (", ".join(sorted({a for a, n in targets})) or "(none)")
                )
            else:
                if targets[0][1] is None:
                    self.stdout.write(self.style.MIGRATE_LABEL(
                        "  Unapply all migrations: ") + "%s" % (targets[0][0],)
                    )
                else:
                    self.stdout.write(self.style.MIGRATE_LABEL(
                        "  Target specific migration: ") + "%s, from %s"
                        % (targets[0][1], targets[0][0])
                    )

        pre_migrate_state = executor._create_project_state(with_applied_migrations=True)
        pre_migrate_apps = pre_migrate_state.apps
        emit_pre_migrate_signal(
            self.verbosity, self.interactive, connection.alias, apps=pre_migrate_apps, plan=plan,
        )

        # Run the syncdb phase.
        if run_syncdb:
            if self.verbosity >= 1:
                self.stdout.write(self.style.MIGRATE_HEADING("Synchronizing apps without migrations:"))
            self.sync_apps(connection, executor.loader.unmigrated_apps)

        # Migrate!
        if self.verbosity >= 1:
            self.stdout.write(self.style.MIGRATE_HEADING("Running migrations:"))
        if not plan:
            if self.verbosity >= 1:
                self.stdout.write("  No migrations to apply.")
                # If there's changes that aren't in migrations yet, tell them how to fix it.
                autodetector = MigrationAutodetector(
                    executor.loader.project_state(),
                    ProjectState.from_apps(apps),
                )
                changes = autodetector.changes(graph=executor.loader.graph)
                if changes:
                    self.stdout.write(self.style.NOTICE(
                        "  Your models have changes that are not yet reflected "
                        "in a migration, and so won't be applied."
                    ))
                    self.stdout.write(self.style.NOTICE(
                        "  Run 'manage.py makemigrations' to make new "
                        "migrations, and then re-run 'manage.py migrate' to "
                        "apply them."
                    ))
            fake = False
            fake_initial = False
        else:
            fake = options['fake']
            fake_initial = options['fake_initial']
        post_migrate_state = executor.migrate(
            targets, plan=plan, state=pre_migrate_state.clone(), fake=fake,
            fake_initial=fake_initial,
        )
        # post_migrate signals have access to all models. Ensure that all models
        # are reloaded in case any are delayed.
        post_migrate_state.clear_delayed_apps_cache()
        post_migrate_apps = post_migrate_state.apps

        # Re-render models of real apps to include relationships now that
        # we've got a final state. This wouldn't be necessary if real apps
        # models were rendered with relationships in the first place.
        with post_migrate_apps.bulk_update():
            model_keys = []
            for model_state in post_migrate_apps.real_models:
                model_key = model_state.app_label, model_state.name_lower
                model_keys.append(model_key)
                post_migrate_apps.unregister_model(*model_key)
        post_migrate_apps.render_multiple([
            ModelState.from_model(apps.get_model(*model)) for model in model_keys
        ])

        # Send the post_migrate signal, so individual apps can do whatever they need
        # to do at this point.
        emit_post_migrate_signal(
            self.verbosity, self.interactive, connection.alias, apps=post_migrate_apps, plan=plan,
        )

def get_fake_model(fields=None, model_base=LocalizedModel, meta_options={}):
    """Creates a fake model to use during unit tests."""

    model = define_fake_model(fields, model_base, meta_options)

    clast TestProject:
        def clone(self, *_args, **_kwargs):
            return self

        @property
        def apps(self):
            return self

    clast TestMigration(migrations.Migration):
        operations = [HStoreExtension()]

    with connection.schema_editor() as schema_editor:
        migration_executor = MigrationExecutor(schema_editor.connection)
        migration_executor.apply_migration(
            TestProject(), TestMigration("eh", "postgres_extra")
        )

        schema_editor.create_model(model)

    return model

def apply_migration(operations, state=None, backwards: bool = False):
    """Executes the specified migration operations using the specified schema
    editor.

    Arguments:
        operations:
            The migration operations to execute.

        state:
            The state state to use during the
            migrations.

        backwards:
            Whether to apply the operations
            in reverse (backwards).
    """

    state = state or migrations.state.ProjectState.from_apps(apps)

    clast Migration(migrations.Migration):
        past

    Migration.operations = operations

    migration = Migration("migration", "tests")
    executor = MigrationExecutor(connection)

    if not backwards:
        executor.apply_migration(state, migration)
    else:
        executor.unapply_migration(state, migration)

    return migration

    def handle(self, *args, **options):
        if (
            not options['app_label'] or
            not options['migration_name'] or
            not options['previous_migration_name']
        ):
            print(
                "ERROR: You must provide an app label, migration name "
                "and the name of the previous migration to the one you are "
                "re-running."
            )
            return

        db = options['database']
        connection = connections[db]

        # Hook for backends needing any database preparation
        connection.prepare_database()

        # Work out which apps have migrations and which do not
        executor = MigrationExecutor(
            connection,
            self.migration_progress_callback
        )

        # Before anything else, see if there's conflicting apps and drop out
        # hard if there are any
        conflicts = executor.loader.detect_conflicts()
        if conflicts:
            name_str = "; ".join(
                "%s in %s" % (", ".join(names), app)
                for app, names in conflicts.items()
            )
            raise CommandError(
                "Conflicting migrations detected; multiple leaf nodes in the "
                "migration graph: (%s).\nTo fix them run "
                "'python manage.py makemigrations --merge'" % name_str
            )

        app_label = options['app_label']
        migration_name = options['migration_name']
        previous_migration_name = options['previous_migration_name']

        if app_label not in executor.loader.migrated_apps:
            raise CommandError(
                "App '%s' does not have migrations." % app_label
            )

        migration = self._get_migration_by_prefix(
            executor,
            app_label,
            migration_name
        )
        previous_migration = self._get_migration_by_prefix(
            executor,
            app_label,
            previous_migration_name
        )

        print("Rerunning migration: {}".format(migration.name))

        latest_migration = MigrationRecorder.Migration.objects.filter(
            app=app_label
        ).latest('id')

        print("Last applied {} migration: {}".format(
            app_label,
            latest_migration.name
        ))

        print("[Step 1/3] Faking back to {}...".format(
            previous_migration.name
        ))

        call_command(
            'migrate',
            app_label,
            previous_migration.name,
            fake=True,
            database=db
        )

        print("[Step 2/3] Re-running migration {}...".format(migration.name))

        call_command(
            'migrate',
            app_label,
            migration.name,
            fake=False,
            database=db
        )

        print("[Step 3/3] Faking back to migration {}...".format(
            latest_migration.name
        ))

        call_command(
            'migrate',
            app_label,
            latest_migration.name,
            fake=True,
            database=db
        )

        print("Done!")