Add an object by id in a ManyToMany relation in Dj

问题:

Django's ManyToMany field can be populated using my_field.add(my_instance), but as I understand it only my_instance.id is actually needed to perform the corresponding SQL query.

If I want to add an object by its id, I can use my_field.add(MyModel.objects.get(id=id)), but this will generate two queries instead of one. How can I avoid this extra query?

回答1:

Although the documentation of the add method does not mention it, you can actually pass directly an id to it, like this:

my_instance.add(id)

Surely, this only works when the primary key is used as the identifier for the relation (the default behaviour).