Remove the 'mqtt.pubsub.by_clientid' option

etc/emq.conf

@@ -1,5 +1,5 @@
 ##===================================================================
-## EMQ Configuration R2.3
+## EMQ Configuration R2.3.0
 ##===================================================================
 
 ##--------------------------------------------------------------------
@@ -288,8 +288,6 @@ mqtt.broker.sys_interval = 60
 ## PubSub Pool Size. Default should be scheduler numbers.
 mqtt.pubsub.pool_size = 8
 
-mqtt.pubsub.by_clientid = true
-
 ## Subscribe Asynchronously
 mqtt.pubsub.async = true
 

priv/emq.schema

@@ -715,11 +715,6 @@ end}.
   {datatype, integer}
 ]}.
 
-{mapping, "mqtt.pubsub.by_clientid", "emqttd.pubsub", [
-  {default, true},
-  {datatype, {enum, [true, false]}}
-]}.
-
 {mapping, "mqtt.pubsub.async", "emqttd.pubsub", [
   {default, true},
   {datatype, {enum, [true, false]}}