Race condition in Django save()

Using Django Using the ORM
1

I have an API that can take a list of files and save it in the DB for a specific user. I want to limit the number of files per user to be some number. The way I enforce this is through overriding the save method: A pseudocode: In the view: For item in list_to_save: item.save()

And save method:

curr_count= Files.objects.filter(id=user_id).count If curr_count > max_count: Get curr_count-max_count item For del in delete: del.delete()

The question is, will this lead to a race condition if the same user tries to send 2 different list of files? Since there might be 2 save operations running at the same time?

I am expecting that there is some race condition since the two server will see that DB has entries, and will try to delete them both, leading to some inconsistencies

2

Yes, this does create a race condition. Since you’re performing an aggregate function (count) on the model, the only way that I can think of to prevent inconsistencies is to acquire a full table lock during your upload processing.