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https://issues.apache.org/jira/browse/CALCITE-3386?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16946175#comment-16946175
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Julian Hyde commented on CALCITE-3386:
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I don't agree. I wish I had seen this earlier. The rationale I stated when I
made this class still applies. CyclicMetadataException is intended for
signaling; it is not an error, most of the time.
I do agree that there are some bugs around cyclic metadata, and I do agree that
they can be difficult to debug. But could the developer fixing that bug make
this change as a patch, while debugging?
> CyclicMetadataException gives misleading stack trace
> ----------------------------------------------------
>
> Key: CALCITE-3386
> URL: https://issues.apache.org/jira/browse/CALCITE-3386
> Project: Calcite
> Issue Type: Bug
> Components: core
> Reporter: Zuozhi Wang
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.22.0
>
> Time Spent: 1.5h
> Remaining Estimate: 0h
>
> Calcite currently reuses the same instance when throwing
> CyclicMetadataException as shown below.
> {code:java}
> /** Singleton instance. Since this exception is thrown for signaling
> purposes, * rather than on an actual error, re-using a singleton instance
> saves the * effort of constructing an exception instance. */
> @SuppressWarnings("ThrowableInstanceNeverThrown")
> public static final CyclicMetadataException INSTANCE = new
> CyclicMetadataException();
> {code}
>
> Reusing the same exception instance gives the wrong stack trace, see:
> [https://stackoverflow.com/questions/15090664/is-it-safe-to-store-an-instance-of-an-exception-and-reuse-it]
> The misleading stack trace causes many confusions when debugging. The
> potential performance impact because of object construction is minor compared
> to the time spent on debugging. Therefore it should be changed to not reuse
> the singleton instance.
> A pull request have been opened to fix this issue:
> [https://github.com/apache/calcite/pull/1484]
>
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