eager-fetch如何才能生效？

对象模型：Customer（客户）拥有多张卡（Card）
关键配置：

<set name="cards" inverse="true" cascade="all,delete-orphan">
	<key column="CUSTOMER_ID" foreign-key="fk_card_customer"/>
	<one-to-many class="Card" />
</set>

<many-to-one name="customer" class="Customer" column="CUSTOMER_ID" fetch="join" lazy="false"/>

hibernate.max_fetch_depth=100
hibernate.default_batch_fetch_size=10

结果是fetch="join"不起作用，执行了如下1+N条sql：

Hibernate: select * from ( select ... from CARD card0_ where 1=1 and card0_.AMOUNT_Y>=? ) where rownum <= ?
Hibernate: select ... from CUSTOMER customer0_ where customer0_.ID=?
Hibernate: select ... from CUSTOMER customer0_ where customer0_.ID=?
Hibernate: select ... from CUSTOMER customer0_ where customer0_.ID=?
Hibernate: select ... from CUSTOMER customer0_ where customer0_.ID=?
Hibernate: select ... from CUSTOMER customer0_ where customer0_.ID=?
Hibernate: select ... from CUSTOMER customer0_ where customer0_.ID=?

用的HQL 还是 Criteria ?

用Criteria马上生效

hql

发现必须显示的写from Card c join c.customer 才行。

Usually, we don't use the mapping document to customize fetching. Instead, we keep the default behavior, and override it for a particular transaction, using left join fetch in HQL. This tells Hibernate to fetch the association eagerly in the first select, using an outer join. In the Criteria query API, you would use setFetchMode(FetchMode.JOIN).

reference上的说明

如果是这样
many-to-one端的fetch="join" 只有在get,load时候才行，这时候去join根本就是副作用，因为get,load查询一条记录，many-to-one也肯定只有一条记录，sql就是1+1 ，分开查询的效率将更高。

retrieval that happens implicitly when an association is navigated --这句话怎么理解？

前提：eager-fetch,使用get 或 load.默认抓取，2条。join.1条
除非是用lazy,用batch initial...，那么通过batch ini..可以一次抓取多个关联对象，语句可能减少。


比如访问一个lazy对象，这个的many-to-one是join

不对吧，hql中的eager-fetch不是这样写的。
请使用 left join fetch