如何修改queryset并将其保存为新对象？ [英] How to modify a queryset and save it as new objects?

问题描述

我需要查询特定模型的一组对象，更改单个属性/列（account），然后将整个查询对象作为新对象/行保存。换句话说，我想复制对象，在重复项上改变一个属性（account）。我基本上是创建一个新帐户，然后通过每个模型，并将以前的帐户的对象复制到新帐户，所以我会反复使用不同的模型，可能使用django shell。我该怎么办？可以在查询级别完成，还是需要遍历所有对象？

I need to query for a set of objects for a particular Model, change a single attribute/column ("account"), and then save the entire queryset's objects as new objects/rows. In other words, I want to duplicate the objects, with a single attribute ("account") changed on the duplicates. I'm basically creating a new account and then going through each model and copying a previous account's objects to the new account, so I'll be doing this repeatedly, with different models, probably using django shell. How should I approach this? Can it be done at the queryset level or do I need to loop through all the objects?

ie

MyModel.objects.filter(account="acct_1")
# Now I need to set account = "acct_2" for the entire queryset, 
# and save as new rows in the database

推荐答案

从 docs ：

如果对象的主键属性未设置，或者如果设置了
记录不存在，Django将执行一个INSERT。

If the object’s primary key attribute is not set, or if it’s set but a record doesn’t exist, Django executes an INSERT.

所以如果你将 id 或 pk 设置为None，它应该可以工作，但是对此解决方案的冲突反应如下：复制模型实例及其相关对象在Django / Algorithm for recusrively dup授权对象

So if you set the id or pk to None it should work, but I've seen conflicting responses to this solution on SO: Duplicating model instances and their related objects in Django / Algorithm for recusrively duplicating an object

此解决方案应该工作（感谢@JoshSmeaton的修复）：

This solution should work (thanks @JoshSmeaton for the fix):

models = MyModel.objects.filter(account="acct_1")
for model in models:
  model.id = None
  model.account = "acct_2"
  model.save()

我想在我的情况下，我有一个 OneToOneField 在我正在测试的模型上，所以我的测试不适用于这个基本的解决方案是有道理的。但是，我相信它应该有效，只要你照顾OneToOneField的。

I think in my case, I have a OneToOneField on the model that I'm testing on, so it makes sense that my test wouldn't work with this basic solution. But, I believe it should work, so long as you take care of OneToOneField's.

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