Django - 在动态模型上指定列顺序

Question

假设我们创建了这样的模型：

def model_factory(*args, **kwargs):
    attrs = {}
    attrs['Meta'] = type('Meta', (object,), {
        'verbose_name': 'My Dynamic model',
        'db_table': 'dynamic_model_table'
    })    

    # Ex. add an arbitrary fields
    attrs['username'] = models.CharField(
        max_length = 128,
        db_column = 'username'
    )
    attrs['email'] = models.CharField(
        max_length = 128,
        db_column = 'email'
    )

    return type('DynamicModel', (models.Model,), attrs)

如何在数据库中指定列顺序？即CREATE语句必须是

CREATE TABLE "dynamic_model_table" (
    "username" varchar(128) NOT NULL,
    "email" varchar(128) NOT NULL
)

然而，使用代码示例，列顺序将是随机的。