[hibernate-issues] [Hibernate-JIRA] Created: (HHH-2346) TableGenerator improvement: set initial value when no record found

[Fabrizio Giustina (JIRA)]

TableGenerator improvement: set initial value when no record found
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         Key: HHH-2346
         URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2346
     Project: Hibernate3
        Type: Patch

  Components: core  
    Versions: 3.2.1    
    Reporter: Fabrizio Giustina
 Attachments: TableGenerator-init.diff

org.hibernate.id.TableGenerator is initialized during SchemaExport by creating a table and inserting 0 as initial value.
When this generator is used to retrieve an id it throws an exception if no existing records are available in such table. Although this is an uncommon situation, it would be better to handle an empty table by simply starting from the default value instead of throwing an exception.

My use case for example is the use of dbunit in a test db: after hibernate starts the db is cleaned up (all the existing records removed) and only data needed a specific test are loaded. Hibernate can't work with an empty hibernate_unique_key and so this table must be handled carefully (excluded from cleanup or added to dbunit test data).

TableGenerator can however be easily modified to gracefully handle such situation: the simple patch attached enhances TableGenerator by trying to insert the missing record instead of immediately throw an exception. This can't hurt existing use cases since the table initialization just saves from an IdentifierGenerationException.

Patch has been generated from hibernate trunk, 8 January 2007

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