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https://issues.apache.org/jira/browse/DERBY-6211?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13687915#comment-13687915
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Rick Hillegas commented on DERBY-6211:
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Thanks for that feedback, Dag. Concerning the experiment you ran when you
traced the same statement twice in a row: I also blundered into this behavior
and came to the same conclusion. The statement is recorded in the trace but the
optimizer is never called because the plan has already been compiled and
cached. As you note, it doesn't matter what kind of tracing you request. A
slight enhancement to your suggestion might be to always skip the statement
cache when optimizer tracing is on. Thanks.
> Make Optimizer trace logic pluggable.
> -------------------------------------
>
> Key: DERBY-6211
> URL: https://issues.apache.org/jira/browse/DERBY-6211
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 10.11.0.0
> Reporter: Rick Hillegas
> Assignee: Rick Hillegas
> Attachments: derby-6211-01-aa-createPlugin.diff,
> derby-6211-02-aa-cleanup.diff, derby-6211-02-ab-cleanup.diff,
> derby-6211-03-aa-customTracer.diff,
> derby-6211-04-aa-moveOptimizerTracerToEngineJar.diff,
> derby-6211-05-aa-xmlOptimizerTracer.diff,
> derby-6211-06-ab-packageProtect-XMLOptTrace.diff
>
>
> Right now the trace logic in the optimizer is hard-coded to produce a stream
> of diagnostics. It would be good to be able to plug alternative trace logic
> into the optimizer. This would make the following possible:
> 1) Plug in trace logic which produces formats which are easier to study and
> which can be analyzed mechanically. E.g., xml formatted output.
> 2) Plug in trace logic which can be used during unit testing to verify that
> the optimizer has picked the right plan. Over time this might make it easier
> to migrate canon-based tests to assertion-based tests.
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