java - GAE Objectify 加载在同一事务内的事务中创建的对象

Question

我尝试使用 objectify 事务，但是当我需要重新加载在同一事务中创建的对象时遇到一些问题。

获取此示例代码

@Entity
public class MyObject
{
    @Parent
    Key<ParentClass> parent;

    @Index
    String foo;
}


ofy().transact(new VoidWork()
{
    @Override
    public void vrun()
    {
        ParentClass parent = load();// load the parent
        String fooValue = "bar";

        Key<ParentClass> parentKey = Key.create(ParentClass.class, parent.getId())
        MyObject myObject = new MyObject(parentKey);
        myObject.setFoo(fooValue);

        ofy().save().entity(myObject).now();

        MyObject reloaded = ofy().load().type(MyObject.class).ancestor(parentKey).filter("foo", fooValue).first().now();

        if(reloaded == null)
        {
            throw new RuntimeException("error");
        }
    }
});

我重新加载的对象始终为空，也许我错过了一些东西，但从逻辑上讲，在事务中我可以查询在同一事务中创建的对象？

谢谢

Answer 1

在这种特殊情况下，Cloud Datastore 与关系数据库不同。该文档指出 -

Unlike with most databases, queries and gets inside a Cloud Datastore transaction do not see the results of previous writes inside that transaction. Specifically, if an entity is modified or deleted within a transaction, a query or lookup returns the original version of the entity as of the beginning of the transaction, or nothing if the entity did not exist then.

https://cloud.google.com/datastore/docs/concepts/transactions#isolation_and_consistency