Merge branch 'feature/mongo_2.6.5_expressions' into feature/mongo_2.6.5_expressions_ifNull_Cond_Not

lib/pipeline/expressions/Expression.js

@@ -203,7 +203,7 @@ klass.registerExpression = function registerExpression(key, parserFunc) {
  */
 klass.parseExpression = function parseExpression(exprElementKey, exprElementValue, vps) {
 	var opName = exprElementKey,
-		op = Expression.expressionParserMap;
+		op = Expression.expressionParserMap[opName];
 	if (!op) throw new Error("invalid operator : " + exprElementKey + "; uassert code 15999");
 
 	// make the expression node