Given simple schema below

Account (1 <--> 0,1) AccountUKData, and they share same primary key. We tested repeately, and getting same result:

1) when first time load Account, hibernate goes to db to retrieve UKData, then cache the Account. Understood.

2) second time we try to load the same account, hibernate returns it from to the cache, [b]but it also goes to db again!![/b], fruitlessly trying to retrieve UKData.

We thought hibernate should be able to know that it's been initialized before, store such info in the cache, so next time it should not intiate the db trip again. It does this for collection associations.

We saw a note in "Changes in version 1.2.1 (31.12.2002)": "fixed a bug caching null-valued one-to-one associations", not sure whether this is the same one just we did something wrong or not.

Any insight will be appreciated.

We are using Hibernate v3.0.5, and EhCache.
Mapping files below,

Account:
<class name="AccountDO" table="ACCOUNT" schema="ACCOUNT">
<cache usage="read-write"/>
<!-- primary key-->
<id name="accountId" column="ACCOUNT_ID" type="int">
<generator class="identity"/>
</id>
....
<one-to-one name="accountUKData"
class="AccountUKData"
cascade="all-delete-orphan"
fetch="join"
/>
...
</class>

AccountUKData:
<class name="AccountUKData" table="ACCOUNT_UK_DATA" schema="ACCOUNT" lazy="true">
<!-- primary key-->
<cache usage="read-write"/>
<id name="accountId" column="ACCOUNT_ID" type="int">
<generator class="foreign">
<param name="property">account</param>
</generator>
</id>
....

<one-to-one name="account"
class="AccountDO"
constrained="true"
/>
</class>

just using session.load(AccountDO.class, new Integer(x)) to load the account.

Thanks!

--Woody

I've been searching a way to do a lazy a "one-to-zero-or-one" relationship in Hibernate and I finally found a way to do it using many-to-one with unique="true". See example below:

Association: Person [1 <--> 0..1] Note




Observe that column "id" is used twice in Person mapping.