Don't fetch subscribers list in room_unused_*

src/mod_muc_admin.erl

@@ -852,6 +852,13 @@ get_all_rooms(Host) ->
 	end, #{}, OnlineRooms),
 
     Mod = gen_mod:db_mod(ServerHost, mod_muc),
+    DbRooms =
+    case erlang:function_exported(Mod, get_rooms_without_subscribers, 2) of
+	true ->
+	    Mod:get_rooms_without_subscribers(ServerHost, Host);
+	_ ->
+	    Mod:get_rooms(ServerHost, Host)
+    end,
     StoredRooms = lists:filtermap(
 	fun(#muc_room{name_host = {Room, _}, opts = Opts}) ->
 	    case maps:is_key(Room, OnlineMap) of
@@ -860,7 +867,7 @@ get_all_rooms(Host) ->
 		_ ->
 		    {true, {Room, Host, ServerHost, Opts}}
 	    end
-	end, Mod:get_rooms(ServerHost, Host)),
+	end, DbRooms),
     OnlineRooms ++ StoredRooms.
 
 get_room_config(Room_pid) ->

src/mod_muc_sql.erl

@@ -36,7 +36,7 @@
 	 get_online_rooms/3, count_online_rooms/2, rsm_supported/0,
 	 register_online_user/4, unregister_online_user/4,
 	 count_online_rooms_by_user/3, get_online_rooms_by_user/3,
-	 get_subscribed_rooms/3]).
+	 get_subscribed_rooms/3, get_rooms_without_subscribers/2]).
 -export([set_affiliation/6, set_affiliations/4, get_affiliation/5,
 	 get_affiliations/3, search_affiliation/4]).
 
@@ -155,6 +155,22 @@ can_use_nick(LServer, Host, JID, Nick) ->
 	_ -> true
     end.
 
+get_rooms_without_subscribers(LServer, Host) ->
+    case catch ejabberd_sql:sql_query(
+	LServer,
+	?SQL("select @(name)s, @(opts)s from muc_room"
+	     " where host=%(Host)s")) of
+	{selected, RoomOpts} ->
+	    lists:map(
+		fun({Room, Opts}) ->
+		    OptsD = ejabberd_sql:decode_term(Opts),
+		    #muc_room{name_host = {Room, Host},
+			      opts = mod_muc:opts_to_binary(OptsD)}
+		end, RoomOpts);
+	_Err ->
+	    []
+    end.
+
 get_rooms(LServer, Host) ->
     case catch ejabberd_sql:sql_query(
                  LServer,