[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-1015) Incorrect SQL generated when one-to-many foreign key is in a discriminated subclass table

[Paul Pogonyshev (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-1015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=32734#action_32734 ] 

Paul Pogonyshev commented on HHH-1015:
--------------------------------------

Why is this 'minor'?  It renders inheritance with discriminator pratctically useless for non-trivial cases, or at least that's how I see it.  And inheritance without discriminator (joined-subclass) gives unbearably huge SQL queries if you have many subclasses...

> Incorrect SQL generated when one-to-many foreign key is in a discriminated subclass table
> -----------------------------------------------------------------------------------------
>
>                 Key: HHH-1015
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1015
>             Project: Hibernate Core
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 3.1 beta 2
>         Environment: Hibernate versions 3.1 beta 3 and 3.0.5
>            Reporter: Steven Grimm
>            Priority: Minor
>         Attachments: hhh-1015-version2.patch, hhh-1015.patch
>
>
> I have the following mappings describing a hierarchy of events and a class that the events refer to:
> <hibernate-mapping package="com.xyz">
>     <class name="Event" table="event" discriminator-value="-1">
>         <id name="Id" type="long" column="event_id"/>
>         <discriminator column="event_type_id" type="integer" />
>         <subclass name="EventPayer" discriminator-value="-3">
>             <join table="event_payer">
>                 <key column="event_id" />
>                 <many-to-one name="payer" column="payer_id" class="Payer" />
>             </join>
>             <subclass name="EventPayerCreated" discriminator-value="1" />
>         </subclass>
>     </class>
>     <class name="Payer" table="payer">
>         <id name="payerId" column="payer_id" type="java.lang.Long"/>
>         <set name="eventPayers" inverse="true" cascade="save-update">
>             <key column="payer_id"/>
>             <one-to-many class="EventPayer"/>
>         </set>
>     </class>
> </hibernate-mapping>
> When I fetch the Payer.eventPayers collection, Hibernate generates this SQL:
> select eventpayer0_.payer_id as payer7_1_,
>     eventpayer0_.event_id as event1_1_,
>     eventpayer0_.event_id as event1_5_0_,
>     eventpayer0_1_.payer_id as payer2_6_0_,
>     eventpayer0_.event_type_id as event2_5_0_
> from event eventpayer0_
> inner join event_payer eventpayer0_1_
>     on eventpayer0_.event_id=eventpayer0_1_.event_id
> where eventpayer0_.payer_id=?
> The problem is that there is no event.payer_id column; payer_id is in the child table, not the parent. It appears that specifying a discriminated subclass in <one-to-many> is the same as specifying the superclass, or that Hibernate is ignoring the subclass's <join> element. As far as I can tell, this leaves no way to resolve bidirectional associations where one end of the association is in a discriminated subclass, which seems like a perfectly reasonable thing to want to do.
> I also tried changing <key column="payer_id"/> to <key property-ref="payer"/> in the Payer class's <set> element, but got similar behavior in the form of a "property not found" error: Hibernate is either looking in the superclass's properties rather than the subclass's or is ignoring the list of properties in the <join> element.

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