[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-2743) NOT NULL columns for "nullable=false" properties not always correct

[Chris Bredesen (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-2743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_27597 ] 

Chris Bredesen commented on HHH-2743:
-------------------------------------

Note that this limitation is listed in section 9.1.1 of the manual:

http://hibernate.org/hib_docs/core/reference/en/html/inheritance.html#inheritance-tableperclass

"Exactly one table is required. There is one big limitation of this mapping strategy: columns declared by the subclasses, such as CCTYPE, may not have NOT NULL constraints."

Whether hibernate should check for this and fail is another question...

> NOT NULL columns for "nullable=false" properties not always correct
> -------------------------------------------------------------------
>
>                 Key: HHH-2743
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2743
>             Project: Hibernate3
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 3.2.4.sp1
>            Reporter: Andreas Schildbach
>         Attachments: problem.zip
>
>
> When Hibernate creates a schema for a "table-per-class-hierarchy" mapping, it does not take into account that some properties might only exist on single branches of that hierarchy.
> Have a look at the attached example (Maven2: mvn eclipse:eclipse to create an eclipse project).
> Classes A and B extend Base. Class A defines a property "a", and B defines b - both with "nullable = false". Hibernate then creates a "NOT NULL" column for those properties. I think this is not correct, because even if instances of A always have that property set it might still be NULL (for instances of B) in the database due to the table-per-class-hierarchy mapping.
> Here is what happens if you start "ProblemTest":
> "Attempt to insert null into a non-nullable column: column: B table: BASE in statement [insert into Base (id, a, class) values (null, ?, 'a')]"
> This is the schema that has been created by Hibernate for HSQLDB:
> create table Base
> (
>   class varchar(31) not null,
>   id integer generated by default as identity (start with 1),
>   a integer not null,
>   b integer not null,
>   primary key (id)
> )

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