From b08bd5a578f55fa711da2f6130f6119c8d093e5f Mon Sep 17 00:00:00 2001
From: Feng <ery.lee@gmail.com>
Date: Sat, 12 Mar 2016 16:38:30 +0800
Subject: [PATCH] retained_message

---
 src/emqttd_backend.erl | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/src/emqttd_backend.erl b/src/emqttd_backend.erl
index df75866cc..9ad03334a 100644
--- a/src/emqttd_backend.erl
+++ b/src/emqttd_backend.erl
@@ -34,6 +34,8 @@
 -export([add_subscription/1, lookup_subscriptions/1, del_subscriptions/1,
          del_subscription/2]).
 
+-record(retained_message, {topic, msg}).
+
 %%--------------------------------------------------------------------
 %% Mnesia callbacks
 %%--------------------------------------------------------------------
@@ -42,9 +44,8 @@ mnesia(boot) ->
     ok = emqttd_mnesia:create_table(retained_message, [
                 {type, ordered_set},
                 {disc_copies, [node()]},
-                {record_name, mqtt_message},
-                {index, [#mqtt_message.topic]},
-                {attributes, record_info(fields, mqtt_message)},
+                {record_name, retained_message},
+                {attributes, record_info(fields, retained_message)},
                 {storage_properties, [{ets, [compressed]},
                                       {dets, [{auto_save, 1000}]}]}]),
     ok = emqttd_mnesia:create_table(backend_subscription, [
@@ -64,17 +65,17 @@ mnesia(copy) ->
 %%--------------------------------------------------------------------
 
 -spec(retain_message(mqtt_message()) -> ok).
-retain_message(Msg) when is_record(Msg, mqtt_message) ->
-    mnesia:dirty_write(retained_message, Msg).
+retain_message(Msg = #mqtt_message{topic = Topic}) ->
+    mnesia:dirty_write(#retained_message{topic = Topic, msg = Msg}).
 
 -spec(read_messages(binary()) -> [mqtt_message()]).
 read_messages(Topic) ->
-    mnesia:dirty_index_read(retained_message, Topic, #mqtt_message.topic).
+    [Msg || #retained_message{msg = Msg} <- mnesia:dirty_read(retained_message, Topic)].
 
 -spec(match_messages(binary()) -> [mqtt_message()]).
 match_messages(Filter) ->
     %% TODO: optimize later...
-    Fun = fun(Msg = #mqtt_message{topic = Name}, Acc) ->
+    Fun = fun(#retained_message{topic = Name, msg = Msg}, Acc) ->
             case emqttd_topic:match(Name, Filter) of
                 true -> [Msg|Acc];
                 false -> Acc
@@ -84,19 +85,18 @@ match_messages(Filter) ->
 
 -spec(delete_message(binary()) -> ok).
 delete_message(Topic) ->
-    %%TODO: no transaction???
-    [mnesia:dirty_delete_object(retained_message, Msg) || Msg <- read_messages(Topic)].
+    mnesia:dirty_delete(retained_message, Topic).
 
 -spec(expire_messages(pos_integer()) -> any()).
 expire_messages(Time) when is_integer(Time) ->
     mnesia:transaction(
         fun() ->
             Match = ets:fun2ms(
-                        fun(#mqtt_message{msgid = MsgId, timestamp = {MegaSecs, Secs, _}})
-                            when Time > (MegaSecs * 1000000 + Secs) -> MsgId
+                        fun(#retained_message{topic = Topic, msg = #mqtt_message{timestamp = {MegaSecs, Secs, _}}})
+                            when Time > (MegaSecs * 1000000 + Secs) -> Topic
                         end),
-            MsgIds = mnesia:select(retained_message, Match, write),
-            lists:foreach(fun(MsgId) -> mnesia:delete({retained_message, MsgId}) end, MsgIds)
+            Topics = mnesia:select(retained_message, Match, write),
+            lists:foreach(fun(Topic) -> mnesia:delete({retained_message, Topic}) end, Topics)
         end).
 
 -spec(retained_count() -> non_neg_integer()).