[hibernate-issues] [Hibernate-JIRA] Commented: (ANN-140) Discriminator column not supported with JOINED strategy

[Pavel (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/ANN-140?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_29542 ] 

Pavel  commented on ANN-140:
----------------------------


It would be nice to see how the problem with the multiple joins is faced when the underlying DB has restriction on the number of joins one can execute in a single SQL? For instance MySQL seems to allow only 31 joins. What happens if the class hierarchy has more than 31 sub-classes?






 

> Discriminator column not supported with JOINED strategy
> -------------------------------------------------------
>
>                 Key: ANN-140
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/ANN-140
>             Project: Hibernate Annotations
>          Issue Type: Bug
>    Affects Versions: 3.1beta6
>         Environment: Hibernate 3.1rc2, Hibernate Annotations 3.1b6
>            Reporter: Steven Grimm
>
> Section 9.1.27 of the EJB3 persistence public draft says, "The DiscriminatorColumn annotation is used to define the discriminator column for SINGLE_TABLE and JOINED mapping strategies." But Hibernate ignores the DiscriminatorColumn annotation when the mapping strategy is JOINED; when a JOINED entity is persisted, its discriminator column is not included in the SQL "insert" statement, resulting in a not-null constraint violation if the discriminator column is marked NOT NULL in the database.
> The JOINED strategy with discriminators is pretty ubiquitous in EJB3 sample code and tutorials out on the net, so lots of people are likely to run into this as they try out EJB3 for the first time. A few examples:
> http://www.oracle.com/technology/tech/java/oc4j/ejb3/howtos-ejb3/howtoejb30inheritance/doc/how-to-ejb30-inheritance.html
> http://www.solarmetric.com/Software/Documentation/4.0.0EA/docs/full/html/ejb3_overview_mapping_discrim.html
> http://www.caucho.com/resin-3.0/amber/tutorial/cmp-inherit/index.xtp

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