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Date: Thu, 12 Apr 2012 19:09:16 +0000 (UTC)
From: "Mike Matrigali (Commented) (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
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Subject: [jira] [Commented] (DERBY-5493) Same value returned by successive
 calls to a sequence generator.
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    [ https://issues.apache.org/jira/browse/DERBY-5493?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13252747#comment-13252747 ] 

Mike Matrigali commented on DERBY-5493:
---------------------------------------

i don't know anything about mac, do you happen to know if writes are properly sync'd on the machine you are using?  It is pretty obvious if you run a simple  derby program that does a commit per very small insert single threaded.  A properly synced machine will quickly become I/O bound somewhere around 
30-100 i/o's per second on regular ide or scsi hardware. maybe just posting results of 1 thread vs 10 threads would be enough in your test, i don't know much about the other configurations.
                
> 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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