Fix iteration in _remove_deleted_email_pushers background job. (#10734)

changelog.d/10734.bugfix

+Remove pushers when deleting a 3pid from an account. Pushers for old unlinked emails will also be deleted.
\ No newline at end of file

synapse/storage/databases/main/pusher.py

@@ -430,10 +430,11 @@ class PusherWorkerStore(SQLBaseStore):
             """
 
             txn.execute(sql, (last_pusher, batch_size))
+            rows = txn.fetchall()
 
             last = None
             num_deleted = 0
-            for row in txn:
+            for row in rows:
                 last = row[0]
                 num_deleted += 1
                 self.db_pool.simple_delete_txn(

tests/push/test_email.py

@@ -344,6 +344,50 @@ class EmailPusherTests(HomeserverTestCase):
         pushers = list(pushers)
         self.assertEqual(len(pushers), 0)
 
+    def test_remove_unlinked_pushers_background_job(self):
+        """Checks that all existing pushers associated with unlinked email addresses are removed
+        upon running the remove_deleted_email_pushers background update.
+        """
+        # disassociate the user's email address manually (without deleting the pusher).
+        # This resembles the old behaviour, which the background update below is intended
+        # to clean up.
+        self.get_success(
+            self.hs.get_datastore().user_delete_threepid(
+                self.user_id, "email", "a@example.com"
+            )
+        )
+
+        # Run the "remove_deleted_email_pushers" background job
+        self.get_success(
+            self.hs.get_datastore().db_pool.simple_insert(
+                table="background_updates",
+                values={
+                    "update_name": "remove_deleted_email_pushers",
+                    "progress_json": "{}",
+                    "depends_on": None,
+                },
+            )
+        )
+
+        # ... and tell the DataStore that it hasn't finished all updates yet
+        self.hs.get_datastore().db_pool.updates._all_done = False
+
+        # Now let's actually drive the updates to completion
+        while not self.get_success(
+            self.hs.get_datastore().db_pool.updates.has_completed_background_updates()
+        ):
+            self.get_success(
+                self.hs.get_datastore().db_pool.updates.do_next_background_update(100),
+                by=0.1,
+            )
+
+        # Check that all pushers with unlinked addresses were deleted
+        pushers = self.get_success(
+            self.hs.get_datastore().get_pushers_by({"user_name": self.user_id})
+        )
+        pushers = list(pushers)
+        self.assertEqual(len(pushers), 0)
+
     def _check_for_mail(self):
         """Check that the user receives an email notification"""