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Hibernate version:

Hibernate 2.1.8

Mapping documents:

see below....

Code between sessionFactory.openSession() and session.close():
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Full stack trace of any exception that occurs:

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I am on a hibernate 2 project and noticed that retrieving an instance of a class with the following set:


<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>

<class name="com.blah.TaskSet" table="mbl_task_set">
<id column="ts_id" name="id">
<generator class="com.blah.TableNextRowIdGenerator">
<param name="name">mbl_task_set</param>
</generator>
</id>
<property name="userName" column="ts_user_name" not-null="true" length="24"/>
<property name="taskSetName" column="ts_name" not-null="true" length="40"/>
<property name="source" column="ts_source" not-null="true" length="10"/>

<set name="paramData" lazy="false" inverse="true" cascade="all">
<key column="tpd_ts_id"/>
<one-to-many class="com.blah.TaskParameterData"/>
</set>
</class>

</hibernate-mapping>



When retrieving the class with the set it Caused the class to do a loop through all above TaskParameterDatas in the set rather than doing a join.


Is this a Hibernate 2 problem that is fixed in Hibernate 3?



See output below:

Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?
Hibernate: select mbl_task0_.tpd_id as tpd_id__, mbl_task0_.tpd_id as tpd_id, mbl_task0_.tpd_ts_id as tpd_ts_id, mbl_task0_.tpd_seq_id as tpd_seq_id, mbl_task0_.tpd_data as tpd_data from mbl_task_param_data mbl_task0_ where mbl_task0_.tpd_ts_id=?

Surely someone has used <set><one-to-many> on Hibernate 2 before ... ???

In my view the proper way is to retain the collection as lasy=true and join the collection when required through a (HQL) query. This avoids possible cartesion-product issues. Most improtantly, this provides the code base with the greatest flexibility and data collection control.

Thanks David for the response.

Even with lazy=false I am still unsure of why Hibernate isn't doing a join. Why would it be running so many select statements?

Thanks,
Josh

dont remember what it is in 2 but on 3 you can say

fetch = "join"...

Why would it be running so many select statements? A: Cartesian product problem ..my guess

Hi,

I hear what your saying about the Cartesian product. I am confused as to why it is doing a cartesian product. I have copied the exact 2 mapping files below....



<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>

<class name="com.blah.TaskParameterData" table="task_param_data">
<id column="tpd_id" name="id">
<generator class="com.blah.TableNextRowIdGenerator">
<param name="name">mbl_task_param_data</param>
</generator>
</id>
<property name="taskSetId" column="tpd_ts_id" not-null="true" length="4"/>
<property name="sequenceId" column="tpd_seq_id" not-null="true" length="4"/>
<property name="data" column="tpd_data" not-null="false"/>
</class>

</hibernate-mapping>






<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>

<class name="com.blah.TaskSet" table="mbl_task_set">
<id column="ts_id" name="id">
<generator class="com.blah.TableNextRowIdGenerator">
<param name="name">task_set</param>
</generator>
</id>
<property name="userName" column="ts_user_name" not-null="true" length="24"/>
<property name="taskSetName" column="ts_name" not-null="true" length="40"/>
<property name="source" column="ts_source" not-null="true" length="10"/>

<set name="paramData" lazy="false" inverse="true" cascade="all">
<key column="tpd_ts_id"/>
<one-to-many class="com.blah.TaskParameterData"/>
</set>
</class>

</hibernate-mapping>




Any ideas?

Thanks,
Josh

Hi Scarface,

I'm a bit confused your post didn't have anything in it other than a direct quote of mine.

Thanks,
Josh

Err .. I meant to say

outer join results in cartesian product

Have a look at the online manual and see the option .

http://www.hibernate.org/hib_docs/reference/en/html/collections.html

Please note the issues that can occur when you have more then one non-lasy collection.

ok i've changed the association to below but the problem still occurs.

<set name="paramData" lazy="true" fetch="join" >
<key column="tpd_ts_id"/>
<one-to-many outer-join="false" class="com.blah.TaskParameterData"/>
</set>


Any further ideas?

change that to

<set name="paramData" fetch="join" >
<key column="tpd_ts_id"/>
<one-to-many class="com.blah.TaskParameterData"/>
</set>

as David said be aware of the consequences when you do this for more than one collections

Unfortunately that did not solve the problem.

Are you sure it isn't the version of Hibernate we are using causing this?

Dude ... post ur mapping files ...

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>

<class name="com.blah.TaskParameterData" table="task_param_data">
<id column="tpd_id" name="id">
<generator class="com.blah.TableNextRowIdGenerator">
<param name="name">mbl_task_param_data</param>
</generator>
</id>
<property name="taskSetId" column="tpd_ts_id" not-null="true" length="4"/>
<property name="sequenceId" column="tpd_seq_id" not-null="true" length="4"/>
<property name="data" column="tpd_data" not-null="false"/>
</class>

</hibernate-mapping>






<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>

<class name="com.blah.TaskSet" table="mbl_task_set">
<id column="ts_id" name="id">
<generator class="com.blah.TableNextRowIdGenerator">
<param name="name">task_set</param>
</generator>
</id>
<property name="userName" column="ts_user_name" not-null="true" length="24"/>
<property name="taskSetName" column="ts_name" not-null="true" length="40"/>
<property name="source" column="ts_source" not-null="true" length="10"/>

<set name="paramData" lazy="false" inverse="true" cascade="all">
<key column="tpd_ts_id"/>
<one-to-many class="com.blah.TaskParameterData"/>
</set>
</class>

</hibernate-mapping>



The java code is:

result = getSession().find("from " + "com.blah.TaskSet");


Thanks