From 1611e3726393bcaf901f1be9dd46a09e496326f9 Mon Sep 17 00:00:00 2001
From: Cathy Teng <cathy.teng@sentry.io>
Date: Thu, 13 Nov 2025 16:00:07 -0800
Subject: [PATCH 1/2] set DetectorGroup detector to null when it's deleted

---
 migrations_lockfile.txt                       |  2 +-
 .../0097_detectorgroup_detector_set_null.py   | 39 +++++++++++++++++++
 .../workflow_engine/models/detector_group.py  |  2 +-
 3 files changed, 41 insertions(+), 2 deletions(-)
 create mode 100644 src/sentry/workflow_engine/migrations/0097_detectorgroup_detector_set_null.py

diff --git a/migrations_lockfile.txt b/migrations_lockfile.txt
index 004bc76f39c766..bb85b7642c256d 100644
--- a/migrations_lockfile.txt
+++ b/migrations_lockfile.txt
@@ -39,4 +39,4 @@ tempest: 0001_squashed_0002_make_message_type_nullable
 
 uptime: 0048_delete_uptime_status_columns
 
-workflow_engine: 0097_add_unique_constraint_to_datasource
+workflow_engine: 0098_detectorgroup_detector_set_null
diff --git a/src/sentry/workflow_engine/migrations/0097_detectorgroup_detector_set_null.py b/src/sentry/workflow_engine/migrations/0097_detectorgroup_detector_set_null.py
new file mode 100644
index 00000000000000..3d0dad5a000e21
--- /dev/null
+++ b/src/sentry/workflow_engine/migrations/0097_detectorgroup_detector_set_null.py
@@ -0,0 +1,39 @@
+# Generated by Django 5.2.1 on 2025-11-13 23:59
+
+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 = False
+
+    dependencies = [
+        ("workflow_engine", "0096_delete_non_single_written_fire_history"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="detectorgroup",
+            name="detector",
+            field=sentry.db.models.fields.foreignkey.FlexibleForeignKey(
+                null=True,
+                on_delete=django.db.models.deletion.SET_NULL,
+                to="workflow_engine.detector",
+            ),
+        ),
+    ]
diff --git a/src/sentry/workflow_engine/models/detector_group.py b/src/sentry/workflow_engine/models/detector_group.py
index 38c3851235a7fd..1fb6651eb93367 100644
--- a/src/sentry/workflow_engine/models/detector_group.py
+++ b/src/sentry/workflow_engine/models/detector_group.py
@@ -12,7 +12,7 @@ class DetectorGroup(DefaultFieldsModel):
 
     __relocation_scope__ = RelocationScope.Excluded
 
-    detector = FlexibleForeignKey("workflow_engine.Detector", on_delete=models.CASCADE)
+    detector = FlexibleForeignKey("workflow_engine.Detector", null=True, on_delete=models.SET_NULL)
     group = FlexibleForeignKey("sentry.Group", on_delete=models.CASCADE)
 
     class Meta:

From 2c878a7ab3c58cf461980aa2917b0edea95762c6 Mon Sep 17 00:00:00 2001
From: Cathy Teng <cathy.teng@sentry.io>
Date: Fri, 14 Nov 2025 09:44:59 -0800
Subject: [PATCH 2/2] fix migratino

---
 ...ctor_set_null.py => 0098_detectorgroup_detector_set_null.py} | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
 rename src/sentry/workflow_engine/migrations/{0097_detectorgroup_detector_set_null.py => 0098_detectorgroup_detector_set_null.py} (95%)

diff --git a/src/sentry/workflow_engine/migrations/0097_detectorgroup_detector_set_null.py b/src/sentry/workflow_engine/migrations/0098_detectorgroup_detector_set_null.py
similarity index 95%
rename from src/sentry/workflow_engine/migrations/0097_detectorgroup_detector_set_null.py
rename to src/sentry/workflow_engine/migrations/0098_detectorgroup_detector_set_null.py
index 3d0dad5a000e21..a446a4160978b9 100644
--- a/src/sentry/workflow_engine/migrations/0097_detectorgroup_detector_set_null.py
+++ b/src/sentry/workflow_engine/migrations/0098_detectorgroup_detector_set_null.py
@@ -23,7 +23,7 @@ class Migration(CheckedMigration):
     is_post_deployment = False
 
     dependencies = [
-        ("workflow_engine", "0096_delete_non_single_written_fire_history"),
+        ("workflow_engine", "0097_add_unique_constraint_to_datasource"),
     ]
 
     operations = [