将消费者定义的聚合（例如SQL计数）与“纯”模型对象结合起来？

What is the best practice of introducing custom (typically volatile) data into entity model classes? This may sound like a bad practice first, but it seems to be quite a common scenario. In our recent web application we have developed a proper model and in most cases we are fine with loading model entities. But there are cases where we cannot afford loading an entire hierarchy of entities; we need to load, say, results of a couple of SQL COUNT’s or possibly some additional information alongside (or embedded inside) the model entities. So basically, the requirements and conditions are:What is the best practice of introducing custom