集合对象上的 JPQL maxResults
我有以下情况：类 Event 具有 Participant 对象的集合，但类 Participant 没有任何对事件的引用。因此，我需要获取给定活动的前 5 位最近参与者，只是不知道如何做到这一点。我知道在完成查询后，我只需要通过在实体管理器中设置 maxResults 来限制结果。这样做的原因是，当我只需要显示 5 个参与者时，让所有参与者始终参与会影响应用程序性能。
使用 JPQL 我可以轻松检索具有给定参与者的事件： select e from Event e where :participant in elements(e.participants) order by e.creationDate desc
但是我如何选择给定事件的参与者，我的意思是在某种程度上让我有可能限制 maxResults 的数量，例如上面的查询？
非常感谢 蒂亚戈
I have the following situation: a class Event that has a collection of Participant objects, but the class Participant don't have any reference to event. So, I need to get the first 5 most recent participants of a given event, just could not figure out how to this. I know that after get the query done I just need to limit the results by setting the maxResults in my entityManager. The reason to do this is because by getting all the participants all the time when I need to show just 5 is impacting application performance.
Using JPQL I can easily retrieve the events that have a given participant:
select e from Event e where :participant in elements(e.participants) order by e.creationDate desc
But how could I select the participants of a given event, I mean in a way that give me the possibility to limit the number maxResults like in the query above?
Many thanks
Thiago
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