[Hibernate-issues] [Hibernate-JIRA] Commented: (ANN-352) Incorrect database sceme created, when using multiple n:m relations between 2 entities

[Emmanuel B. (JIRA) <no...@at...>]

    [ http://opensource.atlassian.com/projects/hibernate/browse/ANN-352?pag=
e=3Dcomments#action_23194 ]=20

Emmanuel Bernard commented on ANN-352:
--------------------------------------

The problem is that implementing something like that is not trivial and wil=
l ovscure the code even more. Not sure it worth it.

> Incorrect database sceme created, when using multiple n:m relations betwe=
en 2 entities
> -------------------------------------------------------------------------=
-------------
>
>          Key: ANN-352
>          URL: http://opensource.atlassian.com/projects/hibernate/browse/A=
NN-352
>      Project: Hibernate Annotations
>         Type: Bug

>     Versions: 3.2.0.cr1
>  Environment: Linux, Java 1.5, Postgresql 8.0
>     Reporter: Erik Tews

>
>
> Hi
> I got 2 entities:
> @Entity
> public class UserBean implements Serializable {
> ....
> @ManyToMany
>     protected Set<LectureBean> getAdminLectures() {
> ....
> @ManyToMany
>     protected Set<LectureBean> getLectures() {
> .... }
> and on the other side
> @Entity=20
> public class LectureBean implements Serializable {
> @ManyToMany(mappedBy=3D"adminLectures", fetch=3DFetchType.LAZY, cascade=
=3DCascadeType.PERSIST)
> protected Set<UserBean> getAdminUsers() {
> @ManyToMany(mappedBy=3D"lectures", fetch=3DFetchType.LAZY, cascade=3DCasc=
adeType.PERSIST)
> protected Set<UserBean> getUsers() {
> ....
> }
> so there are 2 n:m relations between these entities. Hibernate generates =
the following table:
> adminusers_userid | adminlectures_lectureid | users_userid | lectures_lec=
tureid
> so it puts these 2 relations in one table but it adds foreign keys:
>     =C2=BBfk3fb6262a62053223=C2=AB FOREIGN KEY (adminlectures_lectureid) =
REFERENCES lecturebean(lectureid)
>     =C2=BBfk3fb6262a569b3581=C2=AB FOREIGN KEY (users_userid) REFERENCES =
userbean(userid)
>     =C2=BBfk3fb6262afb45c494=C2=AB FOREIGN KEY (lectures_lectureid) REFER=
ENCES lecturebean(lectureid)
>     =C2=BBfk3fb6262a66a3ba50=C2=AB FOREIGN KEY (adminusers_userid) REFERE=
NCES userbean(userid)
> This makes it impossible to put 2 entities in relation, because 2 of the =
4 columns will always be null.
> Adding differen column names for the join tables with @JoinTable works ar=
ound the problem.

--=20
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