"prunenotifications" management command

README.md

@@ -190,6 +190,13 @@ There are separate Django management commands for each task:
     $ ./manage.py pruneemails
     ````
 
+* Remove old records of sent notifications. For each check, remove
+  notifications that are older than the oldest stored ping for same check.
+
+    ````
+    $ ./manage.py prunenotifications
+    ````
+
 * Remove user accounts that match either of these conditions:
  * Account was created more than a month ago, and user has never logged in.
    These can happen when user enters invalid email address when signing up.

hc/api/management/commands/prunenotifications.py

@@ -0,0 +1,22 @@
+from django.core.management.base import BaseCommand
+from django.db.models import Min
+
+from hc.api.models import Notification, Check
+
+
+class Command(BaseCommand):
+    help = 'Prune stored notifications'
+
+    def handle(self, *args, **options):
+        total = 0
+
+        q = Check.objects.filter(n_pings__gt=0)
+        q = q.annotate(min_ping_date=Min("ping__created"))
+        for check in q:
+            qq = Notification.objects.filter(owner_id=check.id,
+                                             created__lt=check.min_ping_date)
+
+            num_deleted, _ = qq.delete()
+            total += num_deleted
+
+        return "Done! Pruned %d notifications." % total