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https://issues.apache.org/jira/browse/DERBY-5493?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13253404#comment-13253404
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Rick Hillegas commented on DERBY-5493:
--------------------------------------
Thanks for that warning about the write-cache on Mac OSX, Mike. I believe that
the write-cache is enabled by default, so that would account for the high
transaction rate.
I have run a similar experiment on a beefier machine (32 processor, Solaris).
The transaction rate is in the range which you would expect for a disabled
write-cache. This experiment ran 32 threads:
java org.apache.derbyTesting.perf.clients.Runner \
-driver org.apache.derby.jdbc.EmbeddedDriver \
-init \
-load seq_gen \
-load_opts
debugging=0,numberOfGenerators=1,tablesPerGenerator=0,insertsPerTransaction=100
\
-gen b2b \
-threads 32 \
I ran the experiment 3 times against the current trunk and then 3 times against
the patch (averaging the results). With the old sequence management (what's
currently in the trunk), I got 49 tx/sec.. With the patch, I got 75 tx/sec..
> 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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