chore(aci): make DetectorGroup unique on Group (#102928)

Author: cathteng

migrations_lockfile.txt

@@ -39,4 +39,4 @@ tempest: 0001_squashed_0002_make_message_type_nullable
 
 uptime: 0048_delete_uptime_status_columns
 
-workflow_engine: 0094_backfill_issue_stream_detector_workflows
+workflow_engine: 0095_unique_detectorgroup_group

src/sentry/workflow_engine/migrations/0095_unique_detectorgroup_group.py

@@ -0,0 +1,42 @@
+# Generated by Django 5.2.1 on 2025-11-06 22:43
+
+import django.db.models.deletion
+from django.db import migrations
+
+import sentry.db.models.fields.foreignkey
+from sentry.new_migrations.migrations import CheckedMigration
+
+
+class Migration(CheckedMigration):
+    # This flag is used to mark that a migration shouldn't be automatically run in production.
+    # This should only be used for operations where it's safe to run the migration after your
+    # code has deployed. So this should not be used for most operations that alter the schema
+    # of a table.
+    # Here are some things that make sense to mark as post deployment:
+    # - Large data migrations. Typically we want these to be run manually so that they can be
+    #   monitored and not block the deploy for a long period of time while they run.
+    # - Adding indexes to large tables. Since this can take a long time, we'd generally prefer to
+    #   run this outside deployments so that we don't block them. Note that while adding an index
+    #   is a schema change, it's completely safe to run the operation after the code has deployed.
+    # Once deployed, run these manually via: https://develop.sentry.dev/database-migrations/#migration-deployment
+
+    is_post_deployment = True
+
+    dependencies = [
+        ("sentry", "1003_group_history_prev_history_safe_removal"),
+        ("workflow_engine", "0094_backfill_issue_stream_detector_workflows"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="detectorgroup",
+            name="group",
+            field=sentry.db.models.fields.foreignkey.FlexibleForeignKey(
+                on_delete=django.db.models.deletion.CASCADE, to="sentry.group", unique=True
+            ),
+        ),
+        migrations.AlterUniqueTogether(
+            name="detectorgroup",
+            unique_together=set(),
+        ),
+    ]

src/sentry/workflow_engine/models/detector_group.py

@@ -13,12 +13,11 @@ class DetectorGroup(DefaultFieldsModel):
     __relocation_scope__ = RelocationScope.Excluded
 
     detector = FlexibleForeignKey("workflow_engine.Detector", on_delete=models.CASCADE)
-    group = FlexibleForeignKey("sentry.Group", on_delete=models.CASCADE)
+    group = FlexibleForeignKey("sentry.Group", on_delete=models.CASCADE, unique=True)
 
     class Meta:
         db_table = "workflow_engine_detectorgroup"
         app_label = "workflow_engine"
-        unique_together = (("detector", "group"),)
         indexes = [
             models.Index(fields=["detector", "-date_added"], name="detectorgroup_det_date_idx"),
         ]