[Hibernate-issues] [Hibernate-JIRA] Commented: (HHH-1926) Mapping a many-to-many to part of the target's composite PK doesn't work

[Daniel H. (JIRA) <no...@at...>]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-1926?page=comments#action_23703 ] 

Daniel Hannum commented on HHH-1926:
------------------------------------

There are countless other JIRA's that provide mapping files and report unexpected behavior. I thought I was fairly clear in my description that I thought it may be a bug. I even provided a test case. 

Where is the line between a support question in the forum and a bug report?

> Mapping a many-to-many to part of the target's composite PK doesn't work 
> -------------------------------------------------------------------------
>
>          Key: HHH-1926
>          URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1926
>      Project: Hibernate3
>         Type: Bug

>   Components: core
>     Versions: 3.1.3
>  Environment: Tested on 3.1.3 and 3.2.0.cr2
>     Reporter: Daniel Hannum
>  Attachments: hibernateTest.zip
>
>
> Hi, I brought this up on the forums:
> http://forum.hibernate.org/viewtopic.php?p=2315103#2315103
> And although I received some guidance, it still doesn't work. Perhaps it's a bug, perhaps it's impossible, perhaps a wider audience can help... here goes.
> Consider 
> class A with a 3-way PK: C1, C2, C3
> class B with a 4-way PK: C2, C3, C4, C5
> As you can see A and B share two columns. This is a many-to-many relation with no join table, and yes I know it's poor database design. It's legacy, can't change it, etc.
> All I want is for Hibernate, when creating a persistent A, to efficiently retrieve a bag of all B's that share the two shared columns. The reverse mapping is optional. I don't need to be able to update this collection, just read the B's without having to issue separate DB hits.
> Unfortunately, Hibernate is still unhappy with my mappings (below)
> org.hibernate.MappingException: collection element mapping has wrong number of columns: hibernatetest.B.relatedAs type: hibernatetest.A
> A.hbm.xml is
> <composite-id name="compId" class="hibernatetest.APK">
> 	<key-property name="column1" column="C1" />
> 	<key-property name="column2" column="C2" />
> 	<key-property name="column3" column="C3" />
> </composite-id>
> <property name="otherColumnA" column="OTHER_COLUMN_A" />
> <properties name="keysSharedA">
> 	<property name="column2" column="C2" insert="false" update="false"/>
> 	<property name="column3" column="C3" insert="false" update="false"/>
> </properties>
> 		
> <bag name="relatedBs">
> 	<key property-ref="keysSharedA">
> 		<column name="C2"/>
> 		<column name="C3"/>
> 	</key>
> 	<many-to-many class="hibernatetest.B"/>
> </bag>
> B.hbm.xml is very similar
> <composite-id name="compId" class="hibernatetest.BPK">
> 	<key-property name="column2" column="C2" />
> 	<key-property name="column3" column="C3" />
> 	<key-property name="column4" column="C4" />
> 	<key-property name="column5" column="C5" />
> </composite-id>
> <property name="otherColumnB" column="OTHER_COLUMN_B" />
> 		
> <properties name="keysSharedB">
> 	<property name="column2" column="C2" insert="false" update="false"/>
> 	<property name="column3" column="C3" insert="false" update="false"/>
> </properties>
> 	
> <bag name="relatedAs" inverse="true">
> 	<key property-ref="keysSharedB">
> 		<column name="C2"/>
> 		<column name="C3"/>
> 	</key>
> 	<many-to-many class="hibernatetest.A"/>
> </bag>
> I have attached a zip containing the code and mapping files, as well as a unit test that displays the problem.
> Thanks for any help you can provide.

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