[hibernate-dev] Unidirectional @OneToMany @JoinColumn associations

[Stephen Fikes]

The only referenced column is one of the *primary* key columns. I left 
out the word "primary" in my previous reply.

To make sure I understand, are you saying that a primary key column 
isn't a primary key column when part of a composite primary key? In 
other words, only the complete set of primary key columns that make up 
the composite primary key would be considered primary key columns and 
the individual primary key columns that make it up would not, 
themselves, be considered primary key columns?

Stephen


On 05/30/2018 03:47 PM, Steve Ebersole wrote:
> 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 
> <mailto: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
>     <mailto: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 <mailto: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 <mailto: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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>     <mailto:hibernate-dev at lists.jboss.org>
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>     >>>>
>     >>>
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