Select_for_update with select_related() with nullable relations

Using Django Using the ORM
1

I have a problem with usage of select_for_update() with select_related() and foreign key can be null. The way with select_for_update(of=(self,)) is not a solution, because I need no lock related rows too. How can I solve this issue in Django?

2

Have you tried Model.objects.select_for_update(of=("self", "related_model")) where related_model is what you’re using in select_related()?

3

This will cause an error, because we try to lock nonexisting row in case related_object is None. We cant use select_for_update with select_related, if related objects can be null. I dont know how to save locks of related objects if they are not null and on the other hand avoid an issue with error.

4

I’ve seen other folks come across this recently. It’s not a Django issue, but a database issue. At a database level, doing a SELECT ... FOR UPDATE with a LEFT JOIN doesn’t work out of the box. I saw a few cases where folks use a view or a nested query to get this to work, but maybe if you search for <your database> select for update with left join, you’ll find more info.