Github user rxin commented on a diff in the pull request: https://github.com/apache/spark/pull/11647#discussion_r55958696 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala --- @@ -598,3 +601,61 @@ abstract class TernaryExpression extends Expression { } } } + +/** + * Rewrites an expression using rules that are guaranteed preserve the result while attempting + * to remove cosmetic variations. Deterministic expressions that are `equal` after canonicalization + * will always return the same answer given the same input (i.e. false positives should not be + * possible). However, it is possible that two canonical expressions that are not equal will in fact + * return the same answer given any input (i.e. false negatives are possible). + * + * The following rules are applied: + * - Names and nullability hints for [[org.apache.spark.sql.types.DataType]]s are stripped. + * - Commutative and associative operations ([[Add]] and [[Multiply]]) have their children ordered + * by `hashCode`. +* - [[EqualTo]] and [[EqualNullSafe]] are reordered by `hashCode`. + * - Other comparisons ([[GreaterThan]], [[LessThan]]) are reversed by `hashCode`. + */ +object Canonicalize extends { --- End diff -- fwiw, if you are keeping this class, i think we should just have it in its own file. The Expression.scala file is getting pretty long.
--- If your project is set up for it, you can reply to this email and have your reply appear on GitHub as well. If your project does not have this feature enabled and wishes so, or if the feature is enabled but not working, please contact infrastructure at infrastruct...@apache.org or file a JIRA ticket with INFRA. --- --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org