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From "Bryan Pendleton (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4849) Re-compilation may cause duplicate entries in the XPLAIN table
Date Thu, 14 Oct 2010 13:26:33 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12920955#action_12920955
] 

Bryan Pendleton commented on DERBY-4849:
----------------------------------------

Thanks Knut Anders, that makes sense. Perhaps we need a way to set an
internal flag in the ResultSet data structure that says "this result set was
opened, but was never actually executed".

Then the code you reference, when raising the NEEDS_RECOMPILE
exception, could look something like:

  this.setPlanWasRecompiled();
  throw LANG_STATEMENT_NEEDS_RECOMPILE...

And the close code that builds the Xplain data could look something like:

  if (!getPlanWasRecompiled()) { ... }

Does that seem like it would work?

> 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
>            Priority: Minor
>         Attachments: 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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