fix(workflows): add detector group caching in ensure_association_with_detector

Author: klochek

src/sentry/workflow_engine/models/detector_group.py

@@ -1,7 +1,10 @@
+from typing import ClassVar, Self
+
 from django.db import models
 
 from sentry.backup.scopes import RelocationScope
 from sentry.db.models import DefaultFieldsModel, FlexibleForeignKey, cell_silo_model
+from sentry.db.models.manager.base import BaseManager
 
 
 @cell_silo_model
@@ -15,6 +18,8 @@ class DetectorGroup(DefaultFieldsModel):
     detector = FlexibleForeignKey("workflow_engine.Detector", null=True, on_delete=models.SET_NULL)
     group = FlexibleForeignKey("sentry.Group", on_delete=models.CASCADE)
 
+    objects: ClassVar[BaseManager[Self]] = BaseManager(cache_fields=("pk", "group"))
+
     class Meta:
         db_table = "workflow_engine_detectorgroup"
         app_label = "workflow_engine"

src/sentry/workflow_engine/processors/detector.py

@@ -636,8 +636,11 @@ def ensure_association_with_detector(group: Group, detector_id: int | None = Non
         return False
 
     # Common case: it exists, we verify and move on.
-    if DetectorGroup.objects.filter(group_id=group.id).exists():
+    try:
+        DetectorGroup.objects.get_from_cache(group=group)
         return True
+    except DetectorGroup.DoesNotExist:
+        pass
 
     # Association is missing, determine the detector_id if not provided
     if detector_id is None: