Don't save all fields of a model when bumping the update date

Instead, use a specialized method that only changes the date. This
provides the following advantages:

* Prevents the date updates from overwriting updates to other fields that
  may happen at the same time.

* Possibly makes the updates more efficient due to fewer columns being
  updated (I have no data on this, though).

* Makes it easier to recognize the purpose of the query when analyzing
  logs/live statistics.

* Makes the purpose of the code more obvious.

The name of the method references the standard POSIX touch utility.

cvat/apps/dataset_manager/task.py

@@ -12,7 +12,6 @@
 
 from django.db import transaction
 from django.db.models.query import Prefetch
-from django.utils import timezone
 from rest_framework.exceptions import ValidationError
 
 from cvat.apps.engine import models, serializers
@@ -389,9 +388,7 @@ def _save_tags_to_db(self, tags):
         self.ir_data.tags = tags
 
     def _set_updated_date(self):
-        db_task = self.db_job.segment.task
-        db_task.updated_date = timezone.now()
-        db_task.save()
+        self.db_job.segment.task.touch()
 
     def _save_to_db(self, data):
         self.reset()
@@ -404,7 +401,7 @@ def _save_to_db(self, data):
     def _create(self, data):
         if self._save_to_db(data):
             self._set_updated_date()
-            self.db_job.save()
+            self.db_job.touch()
 
     def create(self, data):
         self._create(data)

cvat/apps/engine/models.py

@@ -323,6 +323,9 @@ class TimestampedModel(models.Model):
     class Meta:
         abstract = True
 
+    def touch(self) -> None:
+        self.save(update_fields=["updated_date"])
+
 class Project(TimestampedModel):
     name = SafeCharField(max_length=256)
     owner = models.ForeignKey(User, null=True, blank=True,

cvat/apps/engine/signals.py

@@ -32,7 +32,7 @@ def __save_job_handler(instance, created, **kwargs):
 
     if status != db_task.status:
         db_task.status = status
-        db_task.save()
+        db_task.save(update_fields=["status", "updated_date"])
 
 @receiver(post_save, sender=User,
     dispatch_uid=__name__ + ".save_user_handler")
@@ -60,9 +60,8 @@ def __delete_task_handler(instance, **kwargs):
         instance.data.delete()
 
     try:
-        if instance.project: # update project
-            db_project = instance.project
-            db_project.save()
+        if db_project := instance.project: # update project
+            db_project.touch()
     except Project.DoesNotExist:
         pass # probably the project has been deleted
 

cvat/apps/engine/views.py

@@ -894,9 +894,9 @@ def perform_update(self, serializer):
         updated_instance = serializer.instance
 
         if instance.project:
-            instance.project.save()
+            instance.project.touch()
         if updated_instance.project:
-            updated_instance.project.save()
+            updated_instance.project.touch()
 
     @transaction.atomic
     def perform_create(self, serializer, **kwargs):
@@ -905,9 +905,8 @@ def perform_create(self, serializer, **kwargs):
             organization=self.request.iam_context['organization']
         )
 
-        if serializer.instance.project:
-            db_project = serializer.instance.project
-            db_project.save()
+        if db_project := serializer.instance.project:
+            db_project.touch()
             assert serializer.instance.organization == db_project.organization
 
         # Required for the extra summary information added in the queryset
@@ -1944,9 +1943,9 @@ def metadata(self, request, pk):
                     db_data.deleted_frames,
                 ))
                 db_data = serializer.save()
-                db_job.segment.task.save()
+                db_job.segment.task.touch()
                 if db_job.segment.task.project:
-                    db_job.segment.task.project.save()
+                    db_job.segment.task.project.touch()
 
         if hasattr(db_data, 'video'):
             media = [db_data.video]
@@ -2285,10 +2284,10 @@ def perform_destroy(self, instance: models.Label):
                 code=status.HTTP_400_BAD_REQUEST)
 
         if project := instance.project:
-            project.save(update_fields=['updated_date'])
+            project.touch()
             ProjectWriteSerializer(project).update_child_objects_on_labels_update(project)
         elif task := instance.task:
-            task.save(update_fields=['updated_date'])
+            task.touch()
             TaskWriteSerializer(task).update_child_objects_on_labels_update(task)
 
         return super().perform_destroy(instance)