Python django.db.router 模块，allow_migrate_model() 实例源码

def _rename(self, apps, schema_editor, old_model, new_model):
        ContentType = apps.get_model('contenttypes', 'ContentType')
        db = schema_editor.connection.alias
        if not router.allow_migrate_model(db, ContentType):
            return

        try:
            content_type = ContentType.objects.db_manager(db).get_by_natural_key(self.app_label, old_model)
        except ContentType.DoesNotExist:
            pass
        else:
            content_type.model = new_model
            try:
                with transaction.atomic(using=db):
                    content_type.save(update_fields={'model'})
            except IntegrityError:
                # Gracefully fallback if a stale content type causes a
                # conflict as update_contenttypes will take care of asking the
                # user what should be done next.
                content_type.model = old_model
            else:
                # Clear the cache as the `get_by_natual_key()` call will cache
                # the renamed ContentType instance by its old model name.
                ContentType.objects.clear_cache()

def _rename(self, apps, schema_editor, old_model, new_model):
        ContentType = apps.get_model('contenttypes', 'ContentType')
        db = schema_editor.connection.alias
        if not router.allow_migrate_model(db, ContentType):
            return

        try:
            content_type = ContentType.objects.db_manager(db).get_by_natural_key(self.app_label, old_model)
        except ContentType.DoesNotExist:
            pass
        else:
            content_type.model = new_model
            try:
                with transaction.atomic(using=db):
                    content_type.save(update_fields={'model'})
            except IntegrityError:
                # Gracefully fallback if a stale content type causes a
                # conflict as remove_stale_contenttypes will take care of
                # asking the user what should be done next.
                content_type.model = old_model
            else:
                # Clear the cache as the `get_by_natual_key()` call will cache
                # the renamed ContentType instance by its old model name.
                ContentType.objects.clear_cache()

def _rename(self, apps, schema_editor, old_model, new_model):
        ContentType = apps.get_model('contenttypes', 'ContentType')
        db = schema_editor.connection.alias
        if not router.allow_migrate_model(db, ContentType):
            return

        try:
            content_type = ContentType.objects.db_manager(db).get_by_natural_key(self.app_label, old_model)
        except ContentType.DoesNotExist:
            pass
        else:
            content_type.model = new_model
            try:
                with transaction.atomic(using=db):
                    content_type.save(update_fields={'model'})
            except IntegrityError:
                # Gracefully fallback if a stale content type causes a
                # conflict as remove_stale_contenttypes will take care of
                # asking the user what should be done next.
                content_type.model = old_model
            else:
                # Clear the cache as the `get_by_natual_key()` call will cache
                # the renamed ContentType instance by its old model name.
                ContentType.objects.clear_cache()

def _rename(self, apps, schema_editor, old_model, new_model):
        ContentType = apps.get_model('contenttypes', 'ContentType')
        db = schema_editor.connection.alias
        if not router.allow_migrate_model(db, ContentType):
            return

        try:
            content_type = ContentType.objects.db_manager(db).get_by_natural_key(self.app_label, old_model)
        except ContentType.DoesNotExist:
            pass
        else:
            content_type.model = new_model
            try:
                with transaction.atomic(using=db):
                    content_type.save(update_fields={'model'})
            except IntegrityError:
                # Gracefully fallback if a stale content type causes a
                # conflict as update_contenttypes will take care of asking the
                # user what should be done next.
                content_type.model = old_model
            else:
                # Clear the cache as the `get_by_natual_key()` call will cache
                # the renamed ContentType instance by its old model name.
                ContentType.objects.clear_cache()

def _rename(self, apps, schema_editor, old_model, new_model):
        ContentType = apps.get_model('contenttypes', 'ContentType')
        db = schema_editor.connection.alias
        if not router.allow_migrate_model(db, ContentType):
            return

        try:
            content_type = ContentType.objects.db_manager(db).get_by_natural_key(self.app_label, old_model)
        except ContentType.DoesNotExist:
            pass
        else:
            content_type.model = new_model
            try:
                with transaction.atomic(using=db):
                    content_type.save(update_fields={'model'})
            except IntegrityError:
                # Gracefully fallback if a stale content type causes a
                # conflict as update_contenttypes will take care of asking the
                # user what should be done next.
                content_type.model = old_model
            else:
                # Clear the cache as the `get_by_natual_key()` call will cache
                # the renamed ContentType instance by its old model name.
                ContentType.objects.clear_cache()

def _rename(self, apps, schema_editor, old_model, new_model):
        ContentType = apps.get_model('contenttypes', 'ContentType')
        db = schema_editor.connection.alias
        if not router.allow_migrate_model(db, ContentType):
            return

        try:
            content_type = ContentType.objects.db_manager(db).get_by_natural_key(self.app_label, old_model)
        except ContentType.DoesNotExist:
            pass
        else:
            content_type.model = new_model
            try:
                with transaction.atomic(using=db):
                    content_type.save(update_fields={'model'})
            except IntegrityError:
                # Gracefully fallback if a stale content type causes a
                # conflict as remove_stale_contenttypes will take care of
                # asking the user what should be done next.
                content_type.model = old_model
            else:
                # Clear the cache as the `get_by_natual_key()` call will cache
                # the renamed ContentType instance by its old model name.
                ContentType.objects.clear_cache()

def _rename(self, apps, schema_editor, old_model, new_model):
        ContentType = apps.get_model('contenttypes', 'ContentType')
        db = schema_editor.connection.alias
        if not router.allow_migrate_model(db, ContentType):
            return

        try:
            content_type = ContentType.objects.db_manager(db).get_by_natural_key(self.app_label, old_model)
        except ContentType.DoesNotExist:
            pass
        else:
            content_type.model = new_model
            try:
                with transaction.atomic(using=db):
                    content_type.save(update_fields={'model'})
            except IntegrityError:
                # Gracefully fallback if a stale content type causes a
                # conflict as update_contenttypes will take care of asking the
                # user what should be done next.
                content_type.model = old_model
            else:
                # Clear the cache as the `get_by_natual_key()` call will cache
                # the renamed ContentType instance by its old model name.
                ContentType.objects.clear_cache()

def _rename(self, apps, schema_editor, old_model, new_model):
        ContentType = apps.get_model('contenttypes', 'ContentType')
        db = schema_editor.connection.alias
        if not router.allow_migrate_model(db, ContentType):
            return

        try:
            content_type = ContentType.objects.db_manager(db).get_by_natural_key(self.app_label, old_model)
        except ContentType.DoesNotExist:
            pass
        else:
            content_type.model = new_model
            try:
                with transaction.atomic(using=db):
                    content_type.save(update_fields={'model'})
            except IntegrityError:
                # Gracefully fallback if a stale content type causes a
                # conflict as update_contenttypes will take care of asking the
                # user what should be done next.
                content_type.model = old_model
            else:
                # Clear the cache as the `get_by_natual_key()` call will cache
                # the renamed ContentType instance by its old model name.
                ContentType.objects.clear_cache()

def _rename(self, apps, schema_editor, old_model, new_model):
        ContentType = apps.get_model('contenttypes', 'ContentType')
        db = schema_editor.connection.alias
        if not router.allow_migrate_model(db, ContentType):
            return

        try:
            content_type = ContentType.objects.db_manager(db).get_by_natural_key(self.app_label, old_model)
        except ContentType.DoesNotExist:
            pass
        else:
            content_type.model = new_model
            try:
                with transaction.atomic(using=db):
                    content_type.save(update_fields={'model'})
            except IntegrityError:
                # Gracefully fallback if a stale content type causes a
                # conflict as remove_stale_contenttypes will take care of
                # asking the user what should be done next.
                content_type.model = old_model
            else:
                # Clear the cache as the `get_by_natual_key()` call will cache
                # the renamed ContentType instance by its old model name.
                ContentType.objects.clear_cache()

def _rename(self, apps, schema_editor, old_model, new_model):
        ContentType = apps.get_model('contenttypes', 'ContentType')
        db = schema_editor.connection.alias
        if not router.allow_migrate_model(db, ContentType):
            return

        try:
            content_type = ContentType.objects.db_manager(db).get_by_natural_key(self.app_label, old_model)
        except ContentType.DoesNotExist:
            pass
        else:
            content_type.model = new_model
            try:
                with transaction.atomic(using=db):
                    content_type.save(update_fields={'model'})
            except IntegrityError:
                # Gracefully fallback if a stale content type causes a
                # conflict as update_contenttypes will take care of asking the
                # user what should be done next.
                content_type.model = old_model
            else:
                # Clear the cache as the `get_by_natual_key()` call will cache
                # the renamed ContentType instance by its old model name.
                ContentType.objects.clear_cache()

def _rename(self, apps, schema_editor, old_model, new_model):
        ContentType = apps.get_model('contenttypes', 'ContentType')
        db = schema_editor.connection.alias
        if not router.allow_migrate_model(db, ContentType):
            return

        try:
            content_type = ContentType.objects.db_manager(db).get_by_natural_key(self.app_label, old_model)
        except ContentType.DoesNotExist:
            pass
        else:
            content_type.model = new_model
            try:
                with transaction.atomic(using=db):
                    content_type.save(update_fields={'model'})
            except IntegrityError:
                # Gracefully fallback if a stale content type causes a
                # conflict as update_contenttypes will take care of asking the
                # user what should be done next.
                content_type.model = old_model
            else:
                # Clear the cache as the `get_by_natual_key()` call will cache
                # the renamed ContentType instance by its old model name.
                ContentType.objects.clear_cache()

def _rename(self, apps, schema_editor, old_model, new_model):
        ContentType = apps.get_model('contenttypes', 'ContentType')
        db = schema_editor.connection.alias
        if not router.allow_migrate_model(db, ContentType):
            return

        try:
            content_type = ContentType.objects.db_manager(db).get_by_natural_key(self.app_label, old_model)
        except ContentType.DoesNotExist:
            pass
        else:
            content_type.model = new_model
            try:
                with transaction.atomic(using=db):
                    content_type.save(update_fields={'model'})
            except IntegrityError:
                # Gracefully fallback if a stale content type causes a
                # conflict as remove_stale_contenttypes will take care of
                # asking the user what should be done next.
                content_type.model = old_model
            else:
                # Clear the cache as the `get_by_natual_key()` call will cache
                # the renamed ContentType instance by its old model name.
                ContentType.objects.clear_cache()

def _rename(self, apps, schema_editor, old_model, new_model):
        ContentType = apps.get_model('contenttypes', 'ContentType')
        db = schema_editor.connection.alias
        if not router.allow_migrate_model(db, ContentType):
            return

        try:
            content_type = ContentType.objects.db_manager(db).get_by_natural_key(self.app_label, old_model)
        except ContentType.DoesNotExist:
            pass
        else:
            content_type.model = new_model
            try:
                with transaction.atomic(using=db):
                    content_type.save(update_fields={'model'})
            except IntegrityError:
                # Gracefully fallback if a stale content type causes a
                # conflict as remove_stale_contenttypes will take care of
                # asking the user what should be done next.
                content_type.model = old_model
            else:
                # Clear the cache as the `get_by_natual_key()` call will cache
                # the renamed ContentType instance by its old model name.
                ContentType.objects.clear_cache()

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def serialize_db_to_string(self):
        """
        Serializes all data in the database into a JSON string.
        Designed only for test runner usage; will not handle large
        amounts of data.
        """
        # Build list of all apps to serialize
        from django.db.migrations.loader import MigrationLoader
        loader = MigrationLoader(self.connection)
        app_list = []
        for app_config in apps.get_app_configs():
            if (
                app_config.models_module is not None and
                app_config.label in loader.migrated_apps and
                app_config.name not in settings.TEST_NON_SERIALIZED_APPS
            ):
                app_list.append((app_config, None))

        # Make a function to iteratively return every object
        def get_objects():
            for model in serializers.sort_dependencies(app_list):
                if (model._meta.can_migrate(self.connection) and
                        router.allow_migrate_model(self.connection.alias, model)):
                    queryset = model._default_manager.using(self.connection.alias).order_by(model._meta.pk.name)
                    for obj in queryset.iterator():
                        yield obj
        # Serialize to a string
        out = StringIO()
        serializers.serialize("json", get_objects(), indent=None, stream=out)
        return out.getvalue()

def allow_migrate_model(self, connection_alias, model):
        """
        Returns if we're allowed to migrate the model.

        This is a thin wrapper around router.allow_migrate_model() that
        preemptively rejects any proxy, swapped out, or unmanaged model.
        """
        if not model._meta.can_migrate(connection_alias):
            return False

        return router.allow_migrate_model(connection_alias, model)

def inject_rename_contenttypes_operations(plan=None, apps=global_apps, using=DEFAULT_DB_ALIAS, **kwargs):
    """
    Insert a `RenameContentType` operation after every planned `RenameModel`
    operation.
    """
    if plan is None:
        return

    # Determine whether or not the ContentType model is available.
    try:
        ContentType = apps.get_model('contenttypes', 'ContentType')
    except LookupError:
        available = False
    else:
        if not router.allow_migrate_model(using, ContentType):
            return
        available = True

    for migration, backward in plan:
        if ((migration.app_label, migration.name) == ('contenttypes', '0001_initial')):
            # There's no point in going forward if the initial contenttypes
            # migration is unapplied as the ContentType model will be
            # unavailable from this point.
            if backward:
                break
            else:
                available = True
                continue
        # The ContentType model is not available yet.
        if not available:
            continue
        inserts = []
        for index, operation in enumerate(migration.operations):
            if isinstance(operation, migrations.RenameModel):
                operation = RenameContentType(
                    migration.app_label, operation.old_name_lower, operation.new_name_lower
                )
                inserts.append((index + 1, operation))
        for inserted, (index, operation) in enumerate(inserts):
            migration.operations.insert(inserted + index, operation)

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, apps=global_apps, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def inject_rename_contenttypes_operations(plan=None, apps=global_apps, using=DEFAULT_DB_ALIAS, **kwargs):
    """
    Insert a `RenameContentType` operation after every planned `RenameModel`
    operation.
    """
    if plan is None:
        return

    # Determine whether or not the ContentType model is available.
    try:
        ContentType = apps.get_model('contenttypes', 'ContentType')
    except LookupError:
        available = False
    else:
        if not router.allow_migrate_model(using, ContentType):
            return
        available = True

    for migration, backward in plan:
        if ((migration.app_label, migration.name) == ('contenttypes', '0001_initial')):
            # There's no point in going forward if the initial contenttypes
            # migration is unapplied as the ContentType model will be
            # unavailable from this point.
            if backward:
                break
            else:
                available = True
                continue
        # The ContentType model is not available yet.
        if not available:
            continue
        inserts = []
        for index, operation in enumerate(migration.operations):
            if isinstance(operation, migrations.RenameModel):
                operation = RenameContentType(
                    migration.app_label, operation.old_name_lower, operation.new_name_lower
                )
                inserts.append((index + 1, operation))
        for inserted, (index, operation) in enumerate(inserts):
            migration.operations.insert(inserted + index, operation)

def get_contenttypes_and_models(app_config, using, ContentType):
    if not router.allow_migrate_model(using, ContentType):
        return None, None

    ContentType.objects.clear_cache()

    content_types = {
        ct.model: ct
        for ct in ContentType.objects.using(using).filter(app_label=app_config.label)
    }
    app_models = {
        model._meta.model_name: model
        for model in app_config.get_models()
    }
    return content_types, app_models

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, apps=global_apps, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def inject_rename_contenttypes_operations(plan=None, apps=global_apps, using=DEFAULT_DB_ALIAS, **kwargs):
    """
    Insert a `RenameContentType` operation after every planned `RenameModel`
    operation.
    """
    if plan is None:
        return

    # Determine whether or not the ContentType model is available.
    try:
        ContentType = apps.get_model('contenttypes', 'ContentType')
    except LookupError:
        available = False
    else:
        if not router.allow_migrate_model(using, ContentType):
            return
        available = True

    for migration, backward in plan:
        if ((migration.app_label, migration.name) == ('contenttypes', '0001_initial')):
            # There's no point in going forward if the initial contenttypes
            # migration is unapplied as the ContentType model will be
            # unavailable from this point.
            if backward:
                break
            else:
                available = True
                continue
        # The ContentType model is not available yet.
        if not available:
            continue
        inserts = []
        for index, operation in enumerate(migration.operations):
            if isinstance(operation, migrations.RenameModel):
                operation = RenameContentType(
                    migration.app_label, operation.old_name_lower, operation.new_name_lower
                )
                inserts.append((index + 1, operation))
        for inserted, (index, operation) in enumerate(inserts):
            migration.operations.insert(inserted + index, operation)

def get_contenttypes_and_models(app_config, using, ContentType):
    if not router.allow_migrate_model(using, ContentType):
        return None, None

    ContentType.objects.clear_cache()

    content_types = {
        ct.model: ct
        for ct in ContentType.objects.using(using).filter(app_label=app_config.label)
    }
    app_models = {
        model._meta.model_name: model
        for model in app_config.get_models()
    }
    return content_types, app_models

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, apps=global_apps, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def inject_rename_contenttypes_operations(plan=None, apps=global_apps, using=DEFAULT_DB_ALIAS, **kwargs):
    """
    Insert a `RenameContentType` operation after every planned `RenameModel`
    operation.
    """
    if plan is None:
        return

    # Determine whether or not the ContentType model is available.
    try:
        ContentType = apps.get_model('contenttypes', 'ContentType')
    except LookupError:
        available = False
    else:
        if not router.allow_migrate_model(using, ContentType):
            return
        available = True

    for migration, backward in plan:
        if ((migration.app_label, migration.name) == ('contenttypes', '0001_initial')):
            # There's no point in going forward if the initial contenttypes
            # migration is unapplied as the ContentType model will be
            # unavailable from this point.
            if backward:
                break
            else:
                available = True
                continue
        # The ContentType model is not available yet.
        if not available:
            continue
        inserts = []
        for index, operation in enumerate(migration.operations):
            if isinstance(operation, migrations.RenameModel):
                operation = RenameContentType(
                    migration.app_label, operation.old_name_lower, operation.new_name_lower
                )
                inserts.append((index + 1, operation))
        for inserted, (index, operation) in enumerate(inserts):
            migration.operations.insert(inserted + index, operation)

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, apps=global_apps, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def serialize_db_to_string(self):
        """
        Serializes all data in the database into a JSON string.
        Designed only for test runner usage; will not handle large
        amounts of data.
        """
        # Build list of all apps to serialize
        from django.db.migrations.loader import MigrationLoader
        loader = MigrationLoader(self.connection)
        app_list = []
        for app_config in apps.get_app_configs():
            if (
                app_config.models_module is not None and
                app_config.label in loader.migrated_apps and
                app_config.name not in settings.TEST_NON_SERIALIZED_APPS
            ):
                app_list.append((app_config, None))

        # Make a function to iteratively return every object
        def get_objects():
            for model in serializers.sort_dependencies(app_list):
                if (not model._meta.proxy and model._meta.managed and
                        router.allow_migrate_model(self.connection.alias, model)):
                    queryset = model._default_manager.using(self.connection.alias).order_by(model._meta.pk.name)
                    for obj in queryset.iterator():
                        yield obj
        # Serialize to a string
        out = StringIO()
        serializers.serialize("json", get_objects(), indent=None, stream=out)
        return out.getvalue()

def inject_rename_contenttypes_operations(plan=None, apps=global_apps, using=DEFAULT_DB_ALIAS, **kwargs):
    """
    Insert a `RenameContentType` operation after every planned `RenameModel`
    operation.
    """
    if plan is None:
        return

    # Determine whether or not the ContentType model is available.
    try:
        ContentType = apps.get_model('contenttypes', 'ContentType')
    except LookupError:
        available = False
    else:
        if not router.allow_migrate_model(using, ContentType):
            return
        available = True

    for migration, backward in plan:
        if ((migration.app_label, migration.name) == ('contenttypes', '0001_initial')):
            # There's no point in going forward if the initial contenttypes
            # migration is unapplied as the ContentType model will be
            # unavailable from this point.
            if backward:
                break
            else:
                available = True
                continue
        # The ContentType model is not available yet.
        if not available:
            continue
        inserts = []
        for index, operation in enumerate(migration.operations):
            if isinstance(operation, migrations.RenameModel):
                operation = RenameContentType(
                    migration.app_label, operation.old_name_lower, operation.new_name_lower
                )
                inserts.append((index + 1, operation))
        for inserted, (index, operation) in enumerate(inserts):
            migration.operations.insert(inserted + index, operation)

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, apps=global_apps, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def inject_rename_contenttypes_operations(plan=None, apps=global_apps, using=DEFAULT_DB_ALIAS, **kwargs):
    """
    Insert a `RenameContentType` operation after every planned `RenameModel`
    operation.
    """
    if plan is None:
        return

    # Determine whether or not the ContentType model is available.
    try:
        ContentType = apps.get_model('contenttypes', 'ContentType')
    except LookupError:
        available = False
    else:
        if not router.allow_migrate_model(using, ContentType):
            return
        available = True

    for migration, backward in plan:
        if ((migration.app_label, migration.name) == ('contenttypes', '0001_initial')):
            # There's no point in going forward if the initial contenttypes
            # migration is unapplied as the ContentType model will be
            # unavailable from this point.
            if backward:
                break
            else:
                available = True
                continue
        # The ContentType model is not available yet.
        if not available:
            continue
        inserts = []
        for index, operation in enumerate(migration.operations):
            if isinstance(operation, migrations.RenameModel):
                operation = RenameContentType(
                    migration.app_label, operation.old_name_lower, operation.new_name_lower
                )
                inserts.append((index + 1, operation))
        for inserted, (index, operation) in enumerate(inserts):
            migration.operations.insert(inserted + index, operation)

def get_contenttypes_and_models(app_config, using, ContentType):
    if not router.allow_migrate_model(using, ContentType):
        return None, None

    ContentType.objects.clear_cache()

    content_types = {
        ct.model: ct
        for ct in ContentType.objects.using(using).filter(app_label=app_config.label)
    }
    app_models = {
        model._meta.model_name: model
        for model in app_config.get_models()
    }
    return content_types, app_models

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, apps=global_apps, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def allow_migrate_model(self, connection_alias, model):
        """
        Returns if we're allowed to migrate the model.

        This is a thin wrapper around router.allow_migrate_model() that
        preemptively rejects any proxy, swapped out, or unmanaged model.
        """
        if not model._meta.can_migrate(connection_alias):
            return False

        return router.allow_migrate_model(connection_alias, model)

def inject_rename_contenttypes_operations(plan=None, apps=global_apps, using=DEFAULT_DB_ALIAS, **kwargs):
    """
    Insert a `RenameContentType` operation after every planned `RenameModel`
    operation.
    """
    if plan is None:
        return

    # Determine whether or not the ContentType model is available.
    try:
        ContentType = apps.get_model('contenttypes', 'ContentType')
    except LookupError:
        available = False
    else:
        if not router.allow_migrate_model(using, ContentType):
            return
        available = True

    for migration, backward in plan:
        if ((migration.app_label, migration.name) == ('contenttypes', '0001_initial')):
            # There's no point in going forward if the initial contenttypes
            # migration is unapplied as the ContentType model will be
            # unavailable from this point.
            if backward:
                break
            else:
                available = True
                continue
        # The ContentType model is not available yet.
        if not available:
            continue
        inserts = []
        for index, operation in enumerate(migration.operations):
            if isinstance(operation, migrations.RenameModel):
                operation = RenameContentType(
                    migration.app_label, operation.old_name_lower, operation.new_name_lower
                )
                inserts.append((index + 1, operation))
        for inserted, (index, operation) in enumerate(inserts):
            migration.operations.insert(inserted + index, operation)

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, apps=global_apps, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def inject_rename_contenttypes_operations(plan=None, apps=global_apps, using=DEFAULT_DB_ALIAS, **kwargs):
    """
    Insert a `RenameContentType` operation after every planned `RenameModel`
    operation.
    """
    if plan is None:
        return

    # Determine whether or not the ContentType model is available.
    try:
        ContentType = apps.get_model('contenttypes', 'ContentType')
    except LookupError:
        available = False
    else:
        if not router.allow_migrate_model(using, ContentType):
            return
        available = True

    for migration, backward in plan:
        if ((migration.app_label, migration.name) == ('contenttypes', '0001_initial')):
            # There's no point in going forward if the initial contenttypes
            # migration is unapplied as the ContentType model will be
            # unavailable from this point.
            if backward:
                break
            else:
                available = True
                continue
        # The ContentType model is not available yet.
        if not available:
            continue
        inserts = []
        for index, operation in enumerate(migration.operations):
            if isinstance(operation, migrations.RenameModel):
                operation = RenameContentType(
                    migration.app_label, operation.old_name_lower, operation.new_name_lower
                )
                inserts.append((index + 1, operation))
        for inserted, (index, operation) in enumerate(inserts):
            migration.operations.insert(inserted + index, operation)

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, apps=global_apps, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def inject_rename_contenttypes_operations(plan=None, apps=global_apps, using=DEFAULT_DB_ALIAS, **kwargs):
    """
    Insert a `RenameContentType` operation after every planned `RenameModel`
    operation.
    """
    if plan is None:
        return

    # Determine whether or not the ContentType model is available.
    try:
        ContentType = apps.get_model('contenttypes', 'ContentType')
    except LookupError:
        available = False
    else:
        if not router.allow_migrate_model(using, ContentType):
            return
        available = True

    for migration, backward in plan:
        if ((migration.app_label, migration.name) == ('contenttypes', '0001_initial')):
            # There's no point in going forward if the initial contenttypes
            # migration is unapplied as the ContentType model will be
            # unavailable from this point.
            if backward:
                break
            else:
                available = True
                continue
        # The ContentType model is not available yet.
        if not available:
            continue
        inserts = []
        for index, operation in enumerate(migration.operations):
            if isinstance(operation, migrations.RenameModel):
                operation = RenameContentType(
                    migration.app_label, operation.old_name_lower, operation.new_name_lower
                )
                inserts.append((index + 1, operation))
        for inserted, (index, operation) in enumerate(inserts):
            migration.operations.insert(inserted + index, operation)

def get_contenttypes_and_models(app_config, using, ContentType):
    if not router.allow_migrate_model(using, ContentType):
        return None, None

    ContentType.objects.clear_cache()

    content_types = {
        ct.model: ct
        for ct in ContentType.objects.using(using).filter(app_label=app_config.label)
    }
    app_models = {
        model._meta.model_name: model
        for model in app_config.get_models()
    }
    return content_types, app_models

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, apps=global_apps, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def allow_migrate_model(self, connection_alias, model):
        """
        Returns if we're allowed to migrate the model.

        This is a thin wrapper around router.allow_migrate_model() that
        preemptively rejects any proxy, swapped out, or unmanaged model.
        """
        if not model._meta.can_migrate(connection_alias):
            return False

        return router.allow_migrate_model(connection_alias, model)

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT_DB_ALIAS, **kwargs):
    try:
        Site = apps.get_model('sites', 'Site')
    except LookupError:
        return

    if not router.allow_migrate_model(using, Site):
        return

    if not Site.objects.using(using).exists():
        # The default settings set SITE_ID = 1, and some tests in Django's test
        # suite rely on this value. However, if database sequences are reused
        # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that
        # the next id will be 1, so we coerce it. See #15573 and #16353. This
        # can also crop up outside of tests - see #15346.
        if verbosity >= 2:
            print("Creating example.com Site object")
        Site(pk=getattr(settings, 'SITE_ID', 1), domain="example.com", name="example.com").save(using=using)

        # We set an explicit pk instead of relying on auto-incrementation,
        # so we need to reset the database sequence. See #17415.
        sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site])
        if sequence_sql:
            if verbosity >= 2:
                print("Resetting sequence")
            with connections[using].cursor() as cursor:
                for command in sequence_sql:
                    cursor.execute(command)

def serialize_db_to_string(self):
        """
        Serializes all data in the database into a JSON string.
        Designed only for test runner usage; will not handle large
        amounts of data.
        """
        # Build list of all apps to serialize
        from django.db.migrations.loader import MigrationLoader
        loader = MigrationLoader(self.connection)
        app_list = []
        for app_config in apps.get_app_configs():
            if (
                app_config.models_module is not None and
                app_config.label in loader.migrated_apps and
                app_config.name not in settings.TEST_NON_SERIALIZED_APPS
            ):
                app_list.append((app_config, None))

        # Make a function to iteratively return every object
        def get_objects():
            for model in serializers.sort_dependencies(app_list):
                if (model._meta.can_migrate(self.connection) and
                        router.allow_migrate_model(self.connection.alias, model)):
                    queryset = model._default_manager.using(self.connection.alias).order_by(model._meta.pk.name)
                    for obj in queryset.iterator():
                        yield obj
        # Serialize to a string
        out = StringIO()
        serializers.serialize("json", get_objects(), indent=None, stream=out)
        return out.getvalue()