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https://issues.apache.org/jira/browse/DERBY-5493?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13252625#comment-13252625
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Mike Matrigali commented on DERBY-5493:
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rick, should I move forward and fix DERBY-5494 separate from the patch in this
issue? I have been spending time looking at it rather than reviewing this
change? I think i can code rest of that fix today and if tests pass tonight be
ready to checkin tommorow.
I think both my proposed fix and your patch (by using a user level
transaction) are both causing the log to be flushed to avoid the crash problem.
For sequences I assume this is necessary and we will have to pay the
perfomance cost. I don't think there is anyway to solve the crash problem
without forcing the log at commit time of the system catalog update.
> Same value returned by successive calls to a sequence generator.
> ----------------------------------------------------------------
>
> Key: DERBY-5493
> URL: https://issues.apache.org/jira/browse/DERBY-5493
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.6.1.0, 10.6.2.1, 10.7.1.1, 10.8.1.2, 10.8.2.2,
> 10.9.0.0
> Reporter: Rick Hillegas
> Assignee: Rick Hillegas
> Labels: derby_triage10_9
> Attachments: derby-5493-01-aa-correctnessPlusPeekerPlusTest.diff,
> derby-5493-01-ad-simplerApproach.diff,
> derby-5493-01-ae-simplerApproachWithCrashJUnitTest.diff
>
>
> The following script shows the same value being returned from a sequence
> generator by two successive NEXT VALUE FOR calls. Thanks to Knut for finding
> this:
> connect 'jdbc:derby:memory:db;create=true';
> create table t (x int);
> create sequence s;
> autocommit off;
> select count(*) from sys.syssequences with rs;
> values next value for s;
> drop table t;
> rollback;
> -- same value as previous call
> values next value for s;
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