Hibernate version: 3.2.6.ga
Name and version of the database: hsqldb 1.8.0.7

I have two entities related one-to-one


This simple test:


Shows following queries in the log:
select person0_.id as id93_1_, person0_.address_id as address2_93_1_, address1_.id as id92_0_ from Person person0_ left outer join Addr address1_ on person0_.address_id=address1_.id where person0_.id=?
select person0_.id as id93_1_, person0_.address_id as address2_93_1_, address1_.id as id92_0_ from Person person0_ left outer join Addr address1_ on person0_.address_id=address1_.id where person0_.address_id=?

First request contains all the info needed to initialize both objects. What's the purpose of the second query and how to get rid of it?

I try to use hibernate in the highload system, but this feature disturbs to me

Have you tried setting the fetch mode on the association? See http://www.hibernate.org/hib_docs/annot ... c-fetching

The default fetch mode is SELECT and it usually does require one select statement for each referenced object. The reason that the two SQL statements are similar may be that you have no other properties than the id in each class.

I have already tried all combinations of annotations Fetch and LazyToOne. Always it turns out two queries.

Hi,

I did not use annotations for my mapping but this xml mapping works for me:

<hibernate-mapping package="org.hibernate.tutorial.domain">

<class name="Address" table="ADDRESS">
<id name="id" column="ADDRESS_ID">
<generator class="native"/>
</id>
<property name="town"/>
<property name="street" />
<property name="zipCode" />
<one-to-one name="phone" class="Phone" fetch="join" lazy="false"/>
</class>

<class name="Phone" table="PHONE">
<id name="id" column="PHONE_ID">
<generator class="native"/>
</id>
<property name="number"/>
</class>
</hibernate-mapping>

The xml that is generated if I execute session.get(Address.class, 1L) is the following:

select
address0_.ADDRESS_ID as ADDRESS1_0_1_,
address0_.town as town0_1_,
address0_.street as street0_1_,
address0_.zipCode as zipCode0_1_,
phone1_.PHONE_ID as PHONE1_1_0_,
phone1_.number as number1_0_
from
ADDRESS address0_
left outer join
PHONE phone1_
on address0_.ADDRESS_ID=phone1_.PHONE_ID
where
address0_.ADDRESS_ID=?

So, everything you need and only one query.

Greets,
Patrick

You use unidirectional relation, but a problem from the bidirectional

put this in log4j

<category name="org.hibernate.type">
<priority value="trace"/>
</category>

<!--category name="org.hibernate.SQL">
<priority value="debug"/>
</category>


in order to the parameters for the sql. Maybe it will enlight us.

Hibernate: select person0_.id as id93_1_, person0_.address_id as address2_93_1_, address1_.id as id92_0_ from Person person0_ left outer join Addr address1_ on person0_.address_id=address1_.id where person0_.id=?
23:02:27,515 TRACE IntegerType:133 - binding '1' to parameter: 1
23:02:27,515 TRACE IntegerType:172 - returning '1' as column: id92_0_
23:02:27,517 TRACE IntegerType:172 - returning '1' as column: address2_93_1_

Hibernate: select person0_.id as id93_1_, person0_.address_id as address2_93_1_, address1_.id as id92_0_ from Person person0_ left outer join Addr address1_ on person0_.address_id=address1_.id where person0_.address_id=?
23:02:27,520 TRACE IntegerType:133 - binding '1' to parameter: 1
23:02:27,520 TRACE IntegerType:172 - returning '1' as column: id92_0_
23:02:27,520 TRACE IntegerType:172 - returning '1' as column: id93_1