[hibernate-dev] Unidirectional @OneToMany @JoinColumn associations

[Sanne Grinovero]

Hi Gail,

I would not consider it a bug to not have documented that we don't
support some non-mandatory feature.

And it's still optional in JPA 2.2, so I think we're good.

Thanks,
Sanne



On 30 May 2018 at 19:45, Gail Badner <gbadner at redhat.com> wrote:
> Hi Vlad,
>
> Thanks for your answer. There are definitely better ways to model this
> association.
>
> WRT the second example, where the referenced columns are a subset of the PK
> columns -- I understand there are better ways to model this.
>
> In particular, since the subset of PK columns needs to be unique (since
> they are the referenced columns of a @JoinColumn), there is no reason for
> any other columns to be in the PK.
>
> My question is more about what the JPA spec says about whether this should
> be supported.
>
> Regards,
> Gail
>
>
>
>
>
> On Wed, May 30, 2018 at 12:47 AM, Vlad Mihalcea <mihalcea.vlad at gmail.com>
> wrote:
>
>> Hi,
>>
>> For the OneToMany with @JoinColumn, the user can workaround this
>> limitation by just using the @ManyToOne on the child side on any column
>> they want
>> and turning the unidirectional association into a bidirectional one. I
>> remember I tested it and it worked just fine.
>>
>> For the  OneToMany with @JoinTable, the only workaround would be if they
>> map the join table as an entity and use the @ManyToOne on the columns they
>> want
>> the association to be based on.
>>
>> Since unidirectional associations don't perform that well, I'm not sure
>> whether it's worth adding support for these use cases.
>>
>> Vlad
>>
>> On Wed, May 30, 2018 at 9:32 AM, Gail Badner <gbadner at redhat.com> wrote:
>>
>>> Unidirectional OneToMany associations using @JoinColumn that reference
>>> columns that are not PK columns is not currently supported.
>>>
>>> The JPA 2.1 documentation for @JoinTable says:
>>>
>>> "Support for referenced columns that are not primary key columns of the
>>> referenced table is optional. Applications that use such mappings will not
>>> be portable."
>>>
>>> I don't see anything in the user doc that explicitly states that Hibernate
>>> does not support this.
>>>
>>> Is this considered a bug?
>>>
>>> Also, what about a unidirectional OneToMany using a @JoinColumn that
>>> references some, but not all, of primary key columns? Hibernate does not
>>> support that either. Should Hibernate support it since they are primary
>>> key
>>> columns?
>>>
>>> Thanks,
>>> Gail
>>> _______________________________________________
>>> hibernate-dev mailing list
>>> hibernate-dev at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/hibernate-dev
>>>
>>
>>
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