[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-944) In one-to-many relationship (Set, Map, List), let <key> accept <formula> as an alternative to <column>.

[Xavier Brénuchon (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-944?page=comments#action_24360 ] 

Xavier Brénuchon commented on HHH-944:
--------------------------------------

Hello,

I am also very interested by this functionality.

We develop an application which has very strong need for performance with several tens of million recordings. Partitioning is a need. 
Because all my tables have a column of partitioning, I need to use shared composite key attribute for all my relations.

So for a <many-to-many>, I use the example of the doc (23.4.3 :)

<class name="User" table="User">
    <composite-id>
        <key-property name="name"/>
        <key-property name="org"/>
    </composite-id>
    <set name="groups" table="UserGroup">
        <key>
            <column name="userName"/>
            <column name="org"/>
        </key>
        <many-to-many class="Group">
            <column name="groupName"/>
            <formula>org</formula>
        </many-to-many>
    </set>
</class>



For a <many-to-one> I use :
<class name="User" table="User">
    <composite-id>
        <key-property name="name"/>
        <key-property name="org"/>
    </composite-id>
    <many-to-one name="team">
        <formula>org</formula>
        <column name="FK_TEAM"/>
    </many-to-one>
</class>



The only problem is for <one-to-many> because <formula> is not possible in <key> :

<class name="User" table="User">
    <composite-id>
        <key-property name="name"/>
        <key-property name="org"/>
    </composite-id>
    <set name="contrats" cascade="all, delete-orphan">
        <key>
            <!-- formula is not authorized  :( -->
            <formula>org</formula>
            <column name="FK_USER"/>
        </key>
        <one-to-many class="Contrat"/>
    </set>
</class>

<class name="Contrat" table="CONTRAT">
    <composite-id>
        <key-property name="name"/>
        <key-property name="org"/>
    </composite-id>
    <!-- ... -->
</class>



It is a limitation which prevents the use of a effective partitioning in data base.

I carried out a test by modifying the source code of hibernate that can function without many modifications.
Is it possible that Hibernate is enriched by this functionality?



> In one-to-many relationship (Set, Map, List),  let <key> accept <formula> as an alternative to <column>. 
> ---------------------------------------------------------------------------------------------------------
>
>          Key: HHH-944
>          URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-944
>      Project: Hibernate3
>         Type: New Feature

>     Versions: 3.1 rc3
>     Reporter: Etienne Laverdiere

>
>
> As explain in http://forum.hibernate.org/viewtopic.php?t=947249&highlight=&sid=c6df51fcf4a97edac80b76c317c51852 and alternatively in http://forum.hibernate.org/viewtopic.php?t=947145&highlight=&sid=c6df51fcf4a97edac80b76c317c51852, it would be nice if the <key> inside a SET or any collection (one-to-many relationship) could accept a <formula> instead of the column:
> Example:
>  <set name="childrens" lazy="true" inverse="true">
>       <key foreign-key="FinancialTransit">
> <formula>ANY SQL</formula>
>       </key>
>       <one-to-many class="com.eg.Children" />
>    </set>
> instead of :
>  <set name="childrens" lazy="true" inverse="true">
>       <key foreign-key="key1">
>          <column name="key2" scale="10"
>          precision="0" not-null="false" unique="true" />
>       </key>
>       <one-to-many  class="com.eg.Children" />
>    </set>
> It would necessitate to patch the class AbstractCollectionPersister and modify the DTD of hibernate mapping.
> Regards, 
> Etienne

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