[Hibernate-issues] [Hibernate-JIRA] Commented: (HB-226) Duplicate column error reported for discriminator

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The following comment has been added to this issue:

     Author: Tomislav Bodor
    Created: Mon, 4 Aug 2003 8:31 PM
       Body:
Hm... Sorry about the alarm, then. I hope it's not too much trouble.

I got away with it because I used Hibernate only for reading - never attempted to save an object (we use it as a read-only query engine of a sort).

I must say, however, that I have not seen this mentioned anywhere in the documentation. Risking to show my ignorance again, I can understand why you'd want update to be false, but if insert is also set to false, how is the value of this field ever persisted when an instance is created?

Related to this: it appears that duplicate mappings are also reported when a column is both mapped as a property and used as a (foreign) key in a relationship. But in this case it's okay to declare it as non-updatable, non-insertable, I suppose.

I'll be happy to move this to a forum if that would be more appropriate?


Thanks,
Tomislav
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Here is an overview of the issue:
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        Key: HB-226
    Summary: Duplicate column error reported for discriminator
       Type: Bug

     Status: Closed
   Priority: Critical
 Resolution: REJECTED

    Project: Hibernate2
 Components: 
             core
   Versions:
             2.0.2

   Assignee: 
   Reporter: Tomislav Bodor

    Created: Mon, 4 Aug 2003 12:27 AM
    Updated: Mon, 4 Aug 2003 3:53 AM
Environment: Not specific to operating system or particular environment

Description:
It appears that one of the changes in version 2.0.2 was to add a check for repeated column mappings. Unfortunately, declaring a discriminator column counts as mapping, though it does not make the column available in the mapped entity. If such a mapping is added using the property tag, a "Repeated column in mapping..." error is reported.

Upon checking in the CVS repository, the change was made to EntityPersister class, between versions 1.35 and 1.36, to add ckecks for duplicate column mappings. This was relaxed in 1.37, but not sufficiently. It appears that line 703 (in 2.0.2) should be removed:
   distinctColumns.add(discriminatorColumnName);

This issue makes it impossible to map an inheritance hierarchy to a single table and still have the discriminator available through a getter method in the mapped entity.

Could someone please confirm this and issue a fix or suggest a workaround?


Regards,
Tomislav


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