MongoEngine: Replacing get_or_create with upsert/update_one

问题

I understand that get_or_create is now deprecated in favour of using upsert, but how do I make update_one to return the object rather the number of objects modified, and can I just retrieve an object if I don't want to update anything?

e.g.

Model.objects.get_or_create(first_name='John', last_name='Potter', age=40)
# assuming that first_name + last_name + age are enough to uniquiely indentify a person

returns a Model object (a new object if it didn't exist, and existing object if it does). What would be the equivalent of this using the new method?

Model.objects(first_name='John', last_name='Potter', age=40).update_one(upsert=True)
# returns number of objects (1)
Model.objects(first_name='John', last_name='Potter', age=40).update_one(set__first_name='John', set__last_name='Potter', set__age=40,upsert=True)
# returns number of objects (1)

Is there a way to make it return the object, and make it behave exactly like get_or_create?

I couldn't find how to do this in the documentation

回答1:

You are very close but you need to use a findAndModify command via modify rather than an update command.

NewDoc = Model.objects(first_name='John', 
                       last_name='Potter', 
                       age=40).modify(upsert=True, new=True,
                                      set__first_name='John, 
                                      set__last_name='Potter', 
                                      set__age=40,
                                      set_on_insert__newUser=True)

Take note of the first 2 modify kwargs - upsert and new. Also take note of the $setOnInsert operator example which will only set a field if the findAndModify does an upsert.

回答2:

You should look at modify. Passing a new=True you'll get the updated object (or document, in mongodb parlance).

来源：https://stackoverflow.com/questions/25846462/mongoengine-replacing-get-or-create-with-upsert-update-one

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django

mongoengine