How to ensure the data is correct if two DMLs occur simultaneously in Django ORM?-PHP Chinese Network Q&A

MyDjangoproject uses themysqlandInnoDBengines. I have a table as shown below, thequeuefield default value is0

class Task(models.Model): task_id = models.CharField(max_length=32, primary_key=True) queue = models.IntegerField(default=0)

I have two processes, one is to insert a record based on the maximum queue in the table.

max_queue = Task.objects.all().annotate(data=Max('queue')).values('data') queue_number = max_queue[0]['data'] + 1 record = {'task_id':task_id, 'queue': queue_number} Task.objects.create(**record)

Another process is to decrement the value ofqueueby 1for each record wherequeue

is not equal to 0.

query_list = Task.objects.filter(~Q(task_queue=0)) for query in query_list: Task.objects.filter(task_id=task_id).update(queue=query.queue - 1)

What I care about here iswhether these two processes occur at the same time. For example, if the subsequent process wants to decrement each value. At the same time, the first process inserts a new value. In this case, some errors may occur.

what should I do? Anyone has a good idea, thanks in advance.

from django.db import transaction from django.db.models import Q with transaction.atomic(): query_list = Task.objects.select_for_update().filter(~Q(queue=0)) for query in query_list: query.queue -= 1 query.save()