Exclude dormant users from buddy list queries.

If a user has not shown activity in two weeks, we exclude
them from the buddy list.  This should help performance for
large realms and mobile clients.

zerver/models.py

@@ -1430,6 +1430,12 @@ class UserPresence(models.Model):
 
         return UserPresence.get_status_dicts_for_query(query, mobile_user_ids)
 
+    @staticmethod
+    def exclude_old_users(query):
+        # type: (QuerySet) -> QuerySet
+        two_weeks_ago = timezone.now() - datetime.timedelta(weeks=2)
+        return query.filter(timestamp__gte=two_weeks_ago)
+
     @staticmethod
     def get_status_dict_by_realm(realm_id):
         # type: (int) -> DefaultDict[Any, Dict[Any, Any]]
@@ -1437,7 +1443,11 @@ class UserPresence(models.Model):
             user_profile__realm_id=realm_id,
             user_profile__is_active=True,
             user_profile__is_bot=False
-        ).values(
+        )
+
+        query = UserPresence.exclude_old_users(query)
+
+        query = query.values(
             'client__name',
             'status',
             'timestamp',

zerver/tests/test_presence.py

@@ -22,6 +22,7 @@ from zerver.models import (
     Client,
     UserActivity,
     UserProfile,
+    UserPresence,
 )
 
 import datetime
@@ -57,6 +58,40 @@ class TestClientModel(ZulipTestCase):
         client = make_client('some_client')
         self.assertEqual(str(client), u'<Client: some_client>')
 
+class UserPresenceModelTests(ZulipTestCase):
+    def test_date_logic(self):
+        # type: () -> None
+        UserPresence.objects.all().delete()
+
+        email = "hamlet@zulip.com"
+        user_profile = get_user_profile_by_email(email)
+        presence_dct = UserPresence.get_status_dict_by_realm(user_profile.realm_id)
+        self.assertEqual(len(presence_dct), 0)
+
+        self.login(email)
+        result = self.client_post("/json/users/me/presence", {'status': 'active'})
+        self.assert_json_success(result)
+
+        presence_dct = UserPresence.get_status_dict_by_realm(user_profile.realm_id)
+        self.assertEqual(len(presence_dct), 1)
+        self.assertEqual(presence_dct[email]['website']['status'], 'active')
+
+        def back_date(num_weeks):
+            # type: (int) -> None
+            user_presence = UserPresence.objects.filter(user_profile=user_profile)[0]
+            user_presence.timestamp = timezone.now() - datetime.timedelta(weeks=num_weeks)
+            user_presence.save()
+
+        # Simulate the presence being a week old first.  Nothing should change.
+        back_date(num_weeks=1)
+        presence_dct = UserPresence.get_status_dict_by_realm(user_profile.realm_id)
+        self.assertEqual(len(presence_dct), 1)
+
+        # If the UserPresence row is three weeks old, we ignore it.
+        back_date(num_weeks=3)
+        presence_dct = UserPresence.get_status_dict_by_realm(user_profile.realm_id)
+        self.assertEqual(len(presence_dct), 0)
+
 class UserPresenceTests(ZulipTestCase):
     def test_invalid_presence(self):
         # type: () -> None