[GitHub] [calcite] zuozhiw commented on a change in pull request #1484: [CALCITE-3386] CyclicMetadataException singleton instance causes confusion when debugging

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zuozhiw commented on a change in pull request #1484: [CALCITE-3386] CyclicMetadataException singleton instance causes confusion when debugging
URL: https://github.com/apache/calcite/pull/1484#discussion_r331727687
 
 

 ##########
 File path: core/src/main/java/org/apache/calcite/rel/metadata/CyclicMetadataException.java
 ##########
 @@ -21,15 +21,12 @@
  * computing metadata.
  */
 public class CyclicMetadataException extends RuntimeException {
-  /** 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();
-
-  /** Creates a CyclicMetadataException. */
-  private CyclicMetadataException() {
+  /**
+   * Creates a CyclicMetadataException.
+   * Reusing a singleton instance is a bad idea because of wrong stack trace.
+   * See https://stackoverflow.com/questions/15090664
 
 Review comment:
   this is removed from the code and moved to commit message

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