Python django.db.migrations 模块，DeleteModel() 实例源码

def create_drop_model(field, filters: List[str]):
    """Creates and drops a model with the specified field.

    Arguments:
        field:
            The field to include on the
            model to create and drop.

        filters:
            List of strings to filter
            SQL statements on.
    """

    model = define_fake_model({'title': field})

    with filtered_schema_editor(*filters) as (schema_editor, calls):
        execute_migration(schema_editor, [
            migrations.CreateModel(
                model.__name__,
                fields=[
                    ('title', field.clone())
                ]
            ),
            migrations.DeleteModel(
                model.__name__,
            )
        ])

    yield calls

def test_delete_model(self):
        project_state = self.set_up_test_model()
        operation = migrations.DeleteModel("Pony")
        new_state = project_state.clone()
        operation.state_forwards('tests', new_state)
        self.assertTableExists('tests_pony')
        with connection.schema_editor() as editor:
            operation.database_forwards('tests', editor, project_state, new_state)
        self.assertTableNotExists('tests_pony')
        with connection.schema_editor() as editor:
            operation.database_backwards('tests', editor, new_state, project_state)
        self.assertTableExists('tests_pony')

def reduce_model_create_delete(self, operation, other, in_between):
        """
        Folds a CreateModel and a DeleteModel into nothing.
        """
        if (operation.name_lower == other.name_lower and
                not operation.options.get("proxy", False)):
            return []

def reduce_model_alter_delete(self, operation, other, in_between):
        """
        Folds an AlterModelSomething and a DeleteModel into just delete.
        """
        if operation.name_lower == other.name_lower:
            return [other]