diff --git a/lib/cartodb/controllers/map.js b/lib/cartodb/controllers/map.js
index 020a5744..e4f5db46 100644
--- a/lib/cartodb/controllers/map.js
+++ b/lib/cartodb/controllers/map.js
@@ -336,6 +336,7 @@ MapController.prototype.afterLayergroupCreate = function(req, res, mapconfig, la
                 req.profiler.done('queryTablesAndLastUpdated');
             }
             assert.ifError(err);
+            // feed affected tables cache so it can be reused from, for instance, layergroup controller
             self.layergroupAffectedTables.set(dbName, layergroupId, result);
 
             // last update for layergroup cache buster