[GitHub] [calcite] julianhyde commented on a change in pull request #2065: [CALCITE-4073] Add a new component RexNormalize for more effect rex n…

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julianhyde commented on a change in pull request #2065:
URL: https://github.com/apache/calcite/pull/2065#discussion_r456231827



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File path: core/src/main/java/org/apache/calcite/sql/SqlOperator.java
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@@ -929,6 +929,17 @@ public boolean isDeterministic() {
     return true;
   }
 
+  /**
+   * Returns whether a call to this operator is not sensitive to the operands input order.
+   * An operator is symmetrical if the call returns the same result when
+   * the operands are shuffled.
+   *
+   * <p>By default, returns true for {@link SqlKind#SYMMETRICAL}.
+   */
+  public boolean isSymmetrical() {
+    return SqlKind.SYMMETRICAL.contains(kind);

Review comment:
       I'm siding with @danny0405 on this one. His use conforms to the mathematical concept of a [symmetric function](https://en.wikipedia.org/wiki/Symmetric_function).




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