Shared cache for affected tables in layergroup and map controllers

lib/cartodb/cache/layergroup_affected_tables.js

@@ -0,0 +1,22 @@
+function LayergroupAffectedTables() {
+    // layergroupId -> affected tables cache
+    this.cache = {};
+}
+
+module.exports = LayergroupAffectedTables;
+
+LayergroupAffectedTables.prototype.hasAffectedTables = function(dbName, layergroupId) {
+    return this.cache.hasOwnProperty(createKey(dbName, layergroupId));
+};
+
+LayergroupAffectedTables.prototype.set = function(dbName, layergroupId, affectedTables) {
+    this.cache[createKey(dbName, layergroupId)] = affectedTables;
+};
+
+LayergroupAffectedTables.prototype.get = function(dbName, layergroupId) {
+    return this.cache[createKey(dbName, layergroupId)];
+};
+
+function createKey(dbName, layergroupId) {
+    return dbName + ':' + layergroupId;
+}

lib/cartodb/cache/model/database_tables_entry.js

@@ -15,6 +15,10 @@ DatabaseTables.prototype.key = function() {
     }.bind(this));
 };
 
+DatabaseTables.prototype.getCacheChannel = function() {
+    return this.dbName + ':' + this.tableNames.join(',');
+};
+
 function shortHashKey(target) {
     return crypto.createHash('sha256').update(target).digest('base64').substring(0,6);
 }