perf: avoid checking success tasks when save limit is disabled (#255)

- avoid extra queries when checking the count of success in db

Makefile

@@ -2,16 +2,16 @@ dev:
 	docker compose -f web-docker-compose.yaml up
 
 test:
-	docker-compose -f test-services-docker-compose.yaml run --rm django-q2 poetry run pytest
+	docker compose -f test-services-docker-compose.yaml run --rm django-q2 poetry run pytest
 
 shell:
-	docker-compose -f test-services-docker-compose.yaml run --rm django-q2 poetry run python manage.py shell
+	docker compose -f test-services-docker-compose.yaml run --rm django-q2 poetry run python manage.py shell
 
 makemigrations:
-	docker-compose -f test-services-docker-compose.yaml run --rm django-q2 poetry run python manage.py makemigrations
+	docker compose -f test-services-docker-compose.yaml run --rm django-q2 poetry run python manage.py makemigrations
 
 migrate:
-	docker-compose -f test-services-docker-compose.yaml run --rm django-q2 poetry run python manage.py migrate
+	docker compose -f test-services-docker-compose.yaml run --rm django-q2 poetry run python manage.py migrate
 
 createsuperuser:
 	docker compose -f web-docker-compose.yaml run --rm web python manage.py createsuperuser

django_q/monitor.py

@@ -107,13 +107,16 @@ def save_task(task, broker: Broker):
                 value = get_func_repr(value)
             filters[Conf.SAVE_LIMIT_PER] = value
 
-        with db.transaction.atomic(using=db.router.db_for_write(Success)):
+        # check if we should clean the success tasks
-            list(Success.objects.filter(**filters).select_for_update())
+        if Conf.SAVE_LIMIT > 0:
-            if (
+            with db.transaction.atomic(using=db.router.db_for_write(Success)):
-                task["success"]
+                success_tasks_qs = Success.objects.filter(**filters)
-                and 0 < Conf.SAVE_LIMIT <= Success.objects.filter(**filters).count()
+                success_tasks_pks = [
-            ):
+                    success_task.pk
-                Success.objects.filter(**filters).last().delete()
+                    for success_task in success_tasks_qs.select_for_update()
+                ]
+                if task["success"] and len(success_tasks_pks) >= Conf.SAVE_LIMIT:
+                    success_tasks_qs.last().delete()
 
         # check if this task has previous results
         try:

django_q/tests/test_cluster.py

@@ -399,7 +399,7 @@ def test_timeout_task_finishes(broker, cluster_config_timeout, async_task_kwargs
 
 
 @pytest.mark.django_db
-def test_recycle(broker, monkeypatch):
+def test_recycle(broker, monkeypatch, django_assert_num_queries):
     # set up the Sentinel
     broker.list_key = "test_recycle_test:q"
     async_task("django_q.tests.tasks.multiply", 2, 2, broker=broker)
@@ -432,7 +432,8 @@ def test_recycle(broker, monkeypatch):
     monkeypatch.setattr(Conf, "SAVE_LIMIT", 1)
     result_queue.put("STOP")
     # run monitor
-    monitor(result_queue)
+    with django_assert_num_queries(12):
+        monitor(result_queue)
     assert Success.objects.count() == Conf.SAVE_LIMIT
     broker.delete_queue()