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https://issues.apache.org/jira/browse/DERBY-4849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12922554#action_12922554
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Kristian Waagan commented on DERBY-4849:
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Lily,
I can't see any performance issues with this patch. Some of the code is only
executed if there is an exception, and the extra if's are "hidden behind" an
existing if-condition (which is mostly false). Let me know if you were thinking
of something in particular.
As for the testing, it may seem as updating the statistics in a loop is good
enough to trigger the invalidation just at the right spot. Of course, I can't
do it only once due to the timing requirements, so I made the test run both the
select and the invalidation code, in separate threads, in a loop for 10 seconds.
Thanks,
> Re-compilation may cause duplicate entries in the XPLAIN table
> --------------------------------------------------------------
>
> Key: DERBY-4849
> URL: https://issues.apache.org/jira/browse/DERBY-4849
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.6.2.1, 10.7.0.0
> Reporter: Kristian Waagan
> Assignee: Kristian Waagan
> Priority: Minor
> Attachments: derby-4849-1a-narrow_fix.diff,
> derby-4849-2a-broad_fix.diff, derby-4849-2b-broad_fix_with_test.diff,
> derby-4849-2b-broad_fix_with_test.stat,
> derby-4849-xplain_duplicate_stacktrace.txt
>
>
> If happening at the right moment, a re-compilation request may cause
> duplicate entries in the XPLAIN statement tables.
> I have only confirmed this for the SYSXPLAIN_STATEMENTS table, and I do not
> know if the other XPLAIN tables are affected.
> The error is highly intermittent, and so far I have only been able to trigger
> it when testing the automatic index statistics update prototype.
> See the attached stack-trace for some more details.
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