Relax touch

Co-authored-by: Grant Gainey <ggainey@users.noreply.github.com>

Author: mdellweg

CHANGES/+touch.feature

@@ -0,0 +1 @@
+Improve touch performance in highly concurrent content operations.

pulpcore/app/models/content.py

@@ -106,17 +106,25 @@ class BulkTouchQuerySet(models.QuerySet):
     def touch(self):
         """
         Update the ``timestamp_of_interest`` on all objects of the query.
-
-        Postgres' UPDATE call doesn't support order-by. This can (and does) result in deadlocks in
-        high-concurrency environments, when using touch() on overlapping data sets. In order to
-        prevent this, we choose to SELECT FOR UPDATE with SKIP LOCKS == True, and only update
-        the rows that we were able to get locks on. Since a previously-locked-row implies
-        that updating that row's timestamp-of-interest is the responsibility of whoever currently
-        owns it, this results in correct data, while closing the window on deadlocks.
         """
+
+        # Postgres' UPDATE call doesn't support order-by. This can (and does) result in deadlocks in
+        # high-concurrency environments, when using touch() on overlapping data sets. In order to
+        # prevent this, we choose to SELECT FOR UPDATE with SKIP LOCKS == True, and only update
+        # the rows that we were able to get locks on. Since a previously-locked-row implies
+        # that updating that row's timestamp-of-interest is the responsibility of whoever currently
+        # owns it, this results in correct data, while closing the window on deadlocks.
+        # Django requires "select_for_update" to be used in a transaction even if this is a
+        # singular query.
+        # `no_key` translates to `SELECT ... FOR NO KEY UPDATE` and results in a different type of
+        # lock being used. We don't change any primary/foreign keys.
         with transaction.atomic():
-            sub_q = self.order_by("pk").select_for_update(skip_locked=True)
-            return self.filter(pk__in=sub_q).update(timestamp_of_interest=now())
+            sub_q = (
+                self.filter(timestamp_of_interest__lt=now() - datetime.timedelta(hours=1))
+                .order_by("pk")
+                .select_for_update(skip_locked=True, no_key=True)
+            )
+            self.filter(pk__in=sub_q).update(timestamp_of_interest=now())
 
 
 class QueryMixin:
@@ -390,7 +398,9 @@ def from_pulp_temporary_file(cls, temp_file):
 
     def touch(self):
         """Update timestamp_of_interest."""
-        self.save(update_fields=["timestamp_of_interest"])
+        # Touch via the queryset.
+        # We are not interested in the updated value on the python side anyway.
+        self.__class__.objects.filter(pk=self.pk).touch()
 
 
 class PulpTemporaryFile(HandleTempFilesMixin, BaseModel):
@@ -624,7 +634,9 @@ def init_from_artifact_and_relative_path(artifact, relative_path):
 
     def touch(self):
         """Update timestamp_of_interest."""
-        self.save(update_fields=["timestamp_of_interest"])
+        # Touch via the queryset.
+        # We are not interested in the updated value on the python side anyway.
+        self.__class__.objects.filter(pk=self.pk).touch()
 
 
 class ContentArtifact(BaseModel, QueryMixin):