[hibernate-dev] Unidirectional @OneToMany @JoinColumn associations

[Gail Badner]

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
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>
>