数据库 – Django – 模型save()方法是否懒惰？

例如,以下代码示例中的哪一行将django命中数据库？

my_model = MyModel()
my_model.name = 'Jeff Atwood'
my_model.save()
# Some code that is independent of my_model...
model_id = model_instance.id
print (model_id)

解决方法

来自django来源：

django / db / models / base.py,第424-437行：

def save(self,force_insert=False,force_update=False,using=None):
    """
    Saves the current instance. Override this in a subclass if you want to
    control the saving process.

    The 'force_insert' and 'force_update' parameters can be used to insist
    that the "save" must be an SQL insert or update (or equivalent for
    non-SQL backends),respectively. Normally,they should not be set.
    """
    if force_insert and force_update:
        raise ValueError("Cannot force both insert and updating in 
            model saving.")
    self.save_base(using=using,force_insert=force_insert,force_update=force_update)

save.alters_data = True

然后,save_base执行繁重的工作(相同的文件,第439-545行)：

...
transaction.commit_unless_managed(using=using)
...

在django / db / transaction.py,第167-178行,你会发现：

def commit_unless_managed(using=None):
    """
    Commits changes if the system is not in managed transaction mode.
    """
    ...

附：所有行号都适用于django版本(1,3,’alpha’,0).

（编辑：李大同）

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