hsyuan commented on a change in pull request #2065:
URL: https://github.com/apache/calcite/pull/2065#discussion_r456685038
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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:
Well, if you think the meaning the method name `isSymmetrical` conveys
is crystal clear and without any ambiguity...
It has several meanings:
- The one you mentioned above, input order insensitive (forgive my ignorance)
- https://www.thefreedictionary.com/Symetrical or
https://en.wikipedia.org/wiki/Symmetry_(geometry)
- [Symmetric
encryption](https://en.wikipedia.org/wiki/Symmetric-key_algorithm) uses it to
denote encryption and decryption use the same key
I do believe there is a reason Scala renamed `symmetricHash` to
`unorderedHash`,
[Cockroachdb](https://github.com/cockroachdb/cockroach/blob/a6a58f4bd1d6b9a7d9f0de2c690d35b51d4f41ca/pkg/sql/opt/optbuilder/groupby.go#L250)
call the method `isOrderingSensitive` instead of others.
For those who lacks of mathematical background, I don't think it is a good
naming public API, which is not self explanatory.
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