perf(mqtt-caps): save some map builds

apps/emqx/src/emqx_mqtt_caps.erl

@@ -108,23 +108,12 @@ do_check_pub(_Flags, _Caps) ->
     ok_or_error(emqx_types:reason_code()).
 check_sub(ClientInfo = #{zone := Zone}, Topic, SubOpts) ->
     Caps = get_caps(?SUBCAP_KEYS, Zone),
-    Flags = lists:foldl(
-        fun
-            (max_topic_levels, Map) ->
-                Map#{topic_levels => emqx_topic:levels(Topic)};
-            (wildcard_subscription, Map) ->
-                Map#{is_wildcard => emqx_topic:wildcard(Topic)};
-            (shared_subscription, Map) ->
-                Map#{is_shared => maps:is_key(share, SubOpts)};
-            (exclusive_subscription, Map) ->
-                Map#{is_exclusive => maps:get(is_exclusive, SubOpts, false)};
-            %% Ignore
-            (_Key, Map) ->
-                Map
-        end,
-        #{},
-        maps:keys(Caps)
-    ),
+    Flags = #{
+        topic_levels => emqx_topic:levels(Topic),
+        is_wildcard => emqx_topic:wildcard(Topic),
+        is_shared => maps:is_key(share, SubOpts),
+        is_exclusive => maps:get(is_exclusive, SubOpts, false)
+    },
     do_check_sub(Flags, Caps, ClientInfo, Topic).
 
 do_check_sub(#{topic_levels := Levels}, #{max_topic_levels := Limit}, _, _) when