如何在Google App Engine中由ManyToOne方面的父母过滤实体 [英] How to filter entities by their parents in ManyToOne side in Google App Engine

问题描述

我使用Google App Engine。当我试图做这样的JPA查询时：

  SELECT p FROM参与者p 
 WHERE p.party.id =：partyKey AND p.name =：participantName 
  

我得到以下错误：

 产生的原因：org.datanucleus.store.appengine.FatalNucleusUserException：
从参与者p其中p.party.id =：partyKey和p .name =：participantName：
如果嵌入子对象，则只能引用子对象的属性。 
  

我将Party对象的关键字作为参数指定给partyKey命名参数。 p>

模型如下：派对有多个参与者。

我想根据参与者的名称和参与者来查询参与者。我只是无法弄清楚如何使用派对过滤。我有什么选择？

我也尝试了以下查询：

  SELECT FROM Participant p 
 WHERE p.party =：party AND p.name =：participantName 
  

但会导致以下错误：

 原因：org.datanucleus.store.appengine.FatalNucleusUserException： 
 SELECT FROM参与者p WHERE p.party =：派对AND p.name =：参与者名称：
参数值的键没有父项。 
  

解决方案

您可以通过声明父pk来执行祖先查询领域。然后，您可以使用该字段筛选子对象。在文档中检查有关parent-pk的部分。（和是的确定以读此讨论）。

更新：对于JPA，看起来你会这样声明：

  @Extension（vendorName =datanucleus，key =gae.parent-pk）
 private long parentId ; 
  

您可能还想阅读查询关键参数博客帖子。

I use Google App Engine. When I try to do a JPA query like this:

SELECT p FROM Participant p 
WHERE p.party.id = :partyKey AND p.name=:participantName 

I get the following error

Caused by: org.datanucleus.store.appengine.FatalNucleusUserException: 
SELECT FROM Participant p WHERE p.party.id = :partyKey AND p.name=:participantName: 
Can only reference properties of a sub-object if the sub-object is embedded.

I gave the key of the Party object as a parameter to the "partyKey" named parameter.

The model is like this: Party has multiple Participants.

I want to query a participant based on the party and the name of the participant. I just can't figure out how to filter using the party. What options do I have?

I've also tried the following query:

SELECT FROM Participant p 
WHERE p.party = :party AND p.name=:participantName

but it results in the following error:

Caused by: org.datanucleus.store.appengine.FatalNucleusUserException: 
SELECT FROM Participant p WHERE p.party = :party AND p.name=:participantName: 
Key of parameter value does not have a parent.

解决方案

You can do ancestor queries by declaring a parent-pk field. You can then filter the child object using that field. Check the part about "parent-pk" in the documentation (and be sure to read this discussion).

Update: For JPA, it seems you would declare it like this:

@Extension(vendorName="datanucleus", key="gae.parent-pk")
private Long parentId;

You might also want to read the Querying with Key parameters blog post.

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