From c8cd87b21bea2fc4a54353849d0b137f09654b18 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Tue, 30 Aug 2016 11:23:26 +0100
Subject: [PATCH] Comment about message deletion

---
 synapse/handlers/sync.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index a8f8b9a75..14f2032af 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -566,6 +566,9 @@ class SyncHandler(object):
             since_stream_id = int(sync_result_builder.since_token.to_device_key)
 
         if since_stream_id != int(now_token.to_device_key):
+            # We only delete messages when a new message comes in, but that's
+            # fine so long as we delete them at some point.
+
             logger.debug("Deleting messages up to %d", since_stream_id)
             yield self.store.delete_messages_for_device(
                 user_id, device_id, since_stream_id