客观化：通过某种类型的参考（或关键）进行过滤

问题描述

假设我有这些类：

  @Entity class MyEntity {
 @Id String id; 
 @Index Ref<？> REF; 
 
 
 @Entity class Kind2 {
 ... 
} 
  

我可以查询所有 MyEntitiy 对象，其中 ref 引用任何 Kind2 ？如果是这样，怎么样？

解决方案

Moshe的答案确实是正确的。但是，您可以在技术上通过对密钥执行不等式查询来破解某些有用的东西。即，> = KEY（'Kind2'，0）和 。如果你的实体有父母，这会变得更加复杂。

我不会推荐你这样做，除非你真的知道你在做什么。

Say I have these classes:

@Entity class MyEntity {
    @Id String id;
    @Index Ref<?> ref;
}

@Entity class Kind2 {
    ...
}

Can I query for all MyEntitiy objects where ref refers to any instance of Kind2? If so, how?

解决方案

Moshe's answer is really the right one. However, you can technically hack something that works by performing inequality queries on the key. Ie, >= KEY('Kind2', 0) and <= KEY('Kind2', MAX_LONG). This gets significantly more complicated if your entities have parents.

I wouldn't recommend doing this unless you really know what you are doing.

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