Querying different EntitySubclasses in one query

Question

I have 3 entities that have something in common.

@Entity
public class BaseEntity {
    Date updatedAt;
}

@EntitySubclass
public class A extends BaseEntity {
    String someData;
}

@EntitySubclass
public class B extends BaseEntity {
    int someData;
}

@EntitySubclass
public class C extends BaseEntity {
    boolean someData;
}

Can I make one query to create List<BaseEntity> or Query<BaseEntity>?

Supposedly something like this?

ofy().load().type(User.class).filter("updatedAt > ", someDate)

Answer 1

Actually, with Objectify I think you can. Here they give an example:

https://code.google.com/p/objectify-appengine/wiki/Entities#Polymorphism

I think the datastore can't do it natively, but Objectify will setup a structure for you that allows polymorphism anyway.

Answer 2

The other answer is not strictly correct. With Objectify, you can query by kind on a superclass and it will seamlessly query all applicable datastore entities which match the inheriting @Entity annotated classes.