[hibernate-dev] Unidirectional @OneToMany @JoinColumn associations

[Steve Ebersole]

The spec says ".... referenced columns that are not primary key
columns...".  Nothing in here says full or partial.

I completely agree with Sanne - its not a bug and it is something we have
never supported.

On Wed, May 30, 2018 at 3:44 PM Stephen Fikes <sfikes at redhat.com> wrote:

> The referenced attributes *are* key attributes .. just a subset of the
> key. So ... odd mapping ... but I don't think it is included in the
> "optional" category for JPA 2.x.
>
> Stephen
>
>
> On 05/30/2018 03:39 PM, Sanne Grinovero wrote:
> > 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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