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Haisheng Yuan edited comment on CALCITE-3386 at 10/7/19 9:06 PM: ----------------------------------------------------------------- It is an exception, not an error. Throwing a new exception can also be treated as a signal, like FileNotFoundException. https://docs.oracle.com/javase/7/docs/api/java/io/FileNotFoundException.html The only difference is whether we throw a new exception, or throw a singleton exception. Not every developer is aware that the exception was just a signal, not a true exception. was (Author: hyuan): It is an exception, not an error. Throwing an exception can also be treated as a signal, like FileNotFoundException. https://docs.oracle.com/javase/7/docs/api/java/io/FileNotFoundException.html > 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] > -- This message was sent by Atlassian Jira (v8.3.4#803005)