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From "B.J. Reed (JIRA)" <j...@apache.org>
Subject [jira] Created: (OPENJPA-1066) Generated ID starting with 0 can cause unexpected results
Date Wed, 06 May 2009 13:00:32 GMT
Generated ID starting with 0 can cause unexpected results
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                 Key: OPENJPA-1066
                 URL: https://issues.apache.org/jira/browse/OPENJPA-1066
             Project: OpenJPA
          Issue Type: Improvement
          Components: kernel
    Affects Versions: 2.0.0
         Environment: any DB that allows a generated id to start with 0.  And an entity that
maps that generated id to an int instead of an Integer
            Reporter: B.J. Reed
            Priority: Minor
             Fix For: 2.0.0
         Attachments: GeneratedIDStartsWith0.ZIP

Several DB's allow a generated id column to start with 0.

For instance, DB2 allows  "GENERATED ALWAYS AS IDENTITY (START WITH 0)...."

When this is used, the very first object will have an id of 0.  When entities are first created,
the user usually won't fill in the corresponding id field (since it will be generated by the
DB when the entity is put in the DB), so it defaults to 0.  The entity manager then uses this
0 and sees that an entity already exists and will update the old entity in stead of creating
a new one.

This is not a large issue, because a user could simply specify "START WITH 1" as a very simple
workaround or they could use an Integer instead of an int, but it would be nice to fix so
that new users don't hit this problem.

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