diff --git a/apps/emqttd/src/emqttd_cm.erl b/apps/emqttd/src/emqttd_cm.erl
index 395a5ad1c..fbc822203 100644
--- a/apps/emqttd/src/emqttd_cm.erl
+++ b/apps/emqttd/src/emqttd_cm.erl
@@ -22,6 +22,7 @@
 %%% @doc
 %%% emqttd client manager.
 %%%
+%%% TODO: NEED PG_HASH?
 %%% @end
 %%%-----------------------------------------------------------------------------
 -module(emqttd_cm).