[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-3160) Support one-to-many list associations with constraints on both (owner_id, position) and (child_id)

[Martin Garton (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-3160?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=44308#comment-44308 ] 

Martin Garton commented on HHH-3160:
------------------------------------

I got around this in our case by making the child allow nulls for the index column and for the parent foreign key.  Together with setting the relationship as nullable=true on the parent entity, this fixed the problem because the old children get removed from the parent (columns set to null) before the new ones are inserted, so although the old chilren are not deleted until after the new children are inserted, the constraint is never violated.

Having these columns as nullable is not perfect, but better IMO than not having the constraint.

> Support one-to-many list associations with constraints on both (owner_id, position) and (child_id)
> --------------------------------------------------------------------------------------------------
>
>                 Key: HHH-3160
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3160
>             Project: Hibernate Core
>          Issue Type: Sub-task
>            Reporter: Gail Badner
>            Assignee: Gail Badner
>         Attachments: workaround.sql, workaround.sql
>
>
> The logic used for removing entities from one-to-many list associations can cause ConstraintViolationException will be thrown if there are constraints on both (owner_id, position) and (child_id) in the "collection table". If the association is on a join table, the "collection table" is the join table; otherwise, the "collection table" is the child entity table..
> Currently, SchemaExport does not put a constraint on (owner_id, position) when exporting one-to-many list associations on a foreign key. SchemaExport should be updated to also export this constraint.
> See HHH-1268 for a description of how to reproduce this issue.
> For one-to-many list associations on a foreign key, the workaround is to define the unique constraint on (owner_id, position) in the child entity table as deferred. It is assumed that the primary key in the child entity table is the child ID.
> For a one-to-many list association on a join table, the workaround is to define the constraint on (child_id) in the join table as deferred. It is assumed that the primary key in the join table is (owner_id, position).
> If your Dialect does not support deferred constraints,  then the only workaround is to exclude the unique constraint.

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