在Django的ManyToMany关系中按ID添加对象 [英] Add an object by id in a ManyToMany relation in Django

问题描述

Django的ManyToMany字段可以使用my_field.add(my_instance)填充，但据我了解，实际上只需要my_instance.id即可执行相应的SQL查询.

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.

如果要通过其ID添加对象，可以使用my_field.add(MyModel.objects.get(id=id))，但这将生成两个查询，而不是一个查询.如何避免这种额外的查询?

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?

推荐答案

尽管

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)

当然，这仅在将主键用作关系的标识符(默认行为)时有效.

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

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