Django - 模型保存（）方法是否懶惰？

Question

模型保存（）方法在Django懶？

例如，在下面的代碼示例中，django會在數據庫中的哪一行？

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) 

Answer 1

懶惰的保存沒有多大意義，是嗎？ Django的QuerySets是懶惰的，該模型的save方法不是。

從django的源：

django/db/models/base.py，線424-437：

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 

然後，save_base確實繁重（同一個文件，行439-545）：

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

而在django/db/transaction.py，第167-178行，你會發現：

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

---

P.S.所有行號適用於django版本(1, 3, 0, 'alpha', 0)。