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https://issues.apache.org/jira/browse/DERBY-6852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15338817#comment-15338817
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Rick Hillegas commented on DERBY-6852:
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Hi Bryan,
An identity column behaves as though its values are supplied by an internal
sequence generator (see 2011 SQL Standard, part 2, section 4.5.11 Identity
columns).
I think that the behavior you describe is also compliant with the Standard, is
a more straightforward reading of the Standard, is more useful, and is how
other databases behave.
I think that we want only one implementation. So, in the interests of
simplicity, I would support changing the cycling behavior of sequence
generators: Cycle to the minimum value (for ascending sequences and to the
maximum value (for descending sequences).
Thanks,
-Rick
> Allow identity columns to cycle (as defined in SQL:2003)
> --------------------------------------------------------
>
> Key: DERBY-6852
> URL: https://issues.apache.org/jira/browse/DERBY-6852
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Reporter: Peter Hansson
> Assignee: Danoja Dias
>
> Currently when an IDENTITY column reaches its maximum value it will produce
> an error.
> For tables that are used as 'transaction logs' or 'event logs' it often makes
> sense to let the table automatically start over with the first identity value
> again when the max is reached. This would be similar to the CYCLE option on
> Oracle's SEQUENCE and as defined in SQL:2003. And Derby is probably used
> quite often for this purpose, I guess, perhaps even more than other RDBMSs.
> At the moment every developer have to program their own logic for this.
> I propose to introduce the CYCLE option.
> The idea of CYCLE is based on the assumption that there's been a prior
> cleanup in the table rows so that it will be possible to re-use ids that have
> been used previously. If that is not the case - and a rollover happens - then
> a duplicate value error will occur. In this sense it can be argued that the
> CYCLE option will trade a _certain_ error for a _potential_ error. Most Derby
> users would possibly gladly accept such a bargain. In other words: This
> option will greatly enhance the usability of IDENTITY columns.
> The current implementation of IDENTITY columns SQL grammar in Derby is a
> subset of the SQL:2003 standard which is the first of the SQL standards to
> define IDENTITY columns. Interestingly the standard also defines the CYCLE
> option but this was never implemented in Derby. Also see [SQL-99 and SQL-2003
> features mapped to Derby|https://wiki.apache.org/db-derby/SQLvsDerbyFeatures]
> (scroll to T174).
> In other words: The proposal is simply to implement CYCLE as defined in
> SQL:2003.
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