chore: add migration to perform the backfill (#9500)

api/src/backend/api/migrations/0062_backfill_daily_severity_summaries.py

@@ -0,0 +1,30 @@
+# Generated by Django 5.1.14 on 2025-12-10
+
+from django.db import migrations
+from tasks.tasks import backfill_daily_severity_summaries_task
+
+from api.db_router import MainRouter
+from api.rls import Tenant
+
+
+def trigger_backfill_task(apps, schema_editor):
+    """
+    Trigger the backfill task for all tenants.
+
+    This dispatches backfill_daily_severity_summaries_task for each tenant
+    in the system to populate DailySeveritySummary records from historical scans.
+    """
+    tenant_ids = Tenant.objects.using(MainRouter.admin_db).values_list("id", flat=True)
+
+    for tenant_id in tenant_ids:
+        backfill_daily_severity_summaries_task.delay(tenant_id=str(tenant_id), days=90)
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("api", "0061_daily_severity_summary"),
+    ]
+
+    operations = [
+        migrations.RunPython(trigger_backfill_task, migrations.RunPython.noop),
+    ]

api/src/backend/tasks/jobs/backfill.py

@@ -1,6 +1,8 @@
 from collections import defaultdict
+from datetime import timedelta
 
 from django.db.models import Sum
+from django.utils import timezone
 
 from api.db_router import READ_REPLICA_ALIAS
 from api.db_utils import rls_transaction
@@ -186,10 +188,6 @@ def backfill_daily_severity_summaries(tenant_id: str, days: int = None):
     Backfill DailySeveritySummary from completed scans.
     Groups by provider+date, keeps latest scan per day.
     """
-    from datetime import timedelta
-
-    from django.utils import timezone
-
     created_count = 0
     updated_count = 0