我想优化一下性能，但是有一个地方有 2 种写法，我不知道哪种好一点，就是比如有条数据进来，我要先判断这条数据在不在，如果在就更新，不在就直接新建一条
伪代码如下：
方法 1 ）
try: article = Article.objects.get(id=9999) 触发：更新逻辑 except: 触发：新建逻辑 方法 2 ）
article = Article.objects.filter(id=9999) if article.exists(): exist_article = article[0] 触发：更新逻辑 else: 触发：新建逻辑 感觉方法 1 有点奇怪，但是似乎就访问一次数据库，方法二啰嗦一点，不知道有没有老鸟能提供帮助？
Returns a tuple of (object, created), where object is the created or updated object and created is a boolean specifying whether a new object was created.
The update_or_create method tries to fetch an object from database based on the given kwargs. If a match is found, it updates the fields passed in the defaults dictionary.
This is meant as a shortcut to boilerplatish code. For example:
defaults = {‘first_name’: ‘Bob’}
try:
obj = Person.objects.get(first_name=’John’, last_name=’Lennon’)
for key, value in defaults.items():
setattr(obj, key, value)
obj.save()
except Person.DoesNotExist:
new_values = {‘first_name’: ‘John’, ‘last_name’: ‘Lennon’}
new_values.update(defaults)
obj = Person(**new_values)
obj.save()
This pattern gets quite unwieldy as the number of fields in a model goes up. The above example can be rewritten using update_or_create() like so:
obj, created = Person.objects.update_or_create(
first_name=’John’, last_name=’Lennon’,
defaults={‘first_name’: ‘Bob’},
)
For detailed description how names passed in kwargs are resolved see get_or_create().
As described above in get_or_create(), this method is prone to a race-condition which can result in multiple rows being inserted simultaneously if uniqueness is not enforced at the database level.
Like get_or_create() and create(), if you’re using manually specified primary keys and an object needs to be created but the key already exists in the database, an IntegrityError is raised.
用 #13 的方法也可以。