CODEWITHSUNDEEP
django
Buttons840
Buttons840

Reputation: 9637

In Django, if I select_for_update() a particular model instance, will its related model instances be locked as well?

my_model_instance = MyModel.objects.select_for_update().get(id=1)
something_related = my_model_instance.related_thing

In the above code, related_thing is another model instance related to my_model_instance by a foreign key. Since I originally did a select_for_update(), will the related_thing be locked as well?

Upvotes: 2

Views: 1328

Answers (1)

joshua
joshua

Reputation: 2519

No. The example you give will make 2 queries:

SELECT ••• FROM `mymodel` WHERE `mymodel`.`id` = 1 FOR UPDATE;
SELECT ••• FROM `related_thing` WHERE `related_thing`.`id` = ?;

Clearly only the first locks. However, if you use select_related() the single query would be:

SELECT ••• FROM `mymodel` LEFT OUTER JOIN `related_thing` ON (`mymodel`.`related_thing_id` = `related_thing`.`id`) WHERE `mymodel`.`id` = 1 FOR UPDATE;

In which case it would lock related_thing as well (at least in MySQL but it might be db dependent).

Upvotes: 2

Related Questions