1717
1818package org .apache .spark .sql .catalyst .expressions
1919
20- import org .apache .spark .sql .catalyst .rules ._
21-
2220/**
2321 * Rewrites an expression using rules that are guaranteed preserve the result while attempting
2422 * to remove cosmetic variations. Deterministic expressions that are `equal` after canonicalization
@@ -30,52 +28,49 @@ import org.apache.spark.sql.catalyst.rules._
3028 * - Names and nullability hints for [[org.apache.spark.sql.types.DataType ]]s are stripped.
3129 * - Commutative and associative operations ([[Add ]] and [[Multiply ]]) have their children ordered
3230 * by `hashCode`.
33- * - [[EqualTo ]] and [[EqualNullSafe ]] are reordered by `hashCode`.
31+ * - [[EqualTo ]] and [[EqualNullSafe ]] are reordered by `hashCode`.
3432 * - Other comparisons ([[GreaterThan ]], [[LessThan ]]) are reversed by `hashCode`.
3533 */
36- object Canonicalize extends RuleExecutor [Expression ] {
37- override protected def batches : Seq [Batch ] =
38- Batch (
39- " Expression Canonicalization" FixedPoint (100 ),
40- IgnoreNamesTypes ,
41- Reorder ) :: Nil
34+ object Canonicalize extends {
35+ def execute (e : Expression ): Expression = {
36+ expressionReorder(ignoreNamesTypes(e))
37+ }
4238
4339 /** Remove names and nullability from types. */
44- protected object IgnoreNamesTypes extends Rule [Expression ] {
45- override def apply (e : Expression ): Expression = e transformUp {
46- case a : AttributeReference =>
47- AttributeReference (" none" = a.exprId)
48- }
40+ private def ignoreNamesTypes (e : Expression ): Expression = e match {
41+ case a : AttributeReference =>
42+ AttributeReference (" none" = a.exprId)
43+ case _ => e
4944 }
5045
5146 /** Collects adjacent commutative operations. */
52- protected def gatherCommutative (
47+ private def gatherCommutative (
5348 e : Expression ,
5449 f : PartialFunction [Expression , Seq [Expression ]]): Seq [Expression ] = e match {
5550 case c if f.isDefinedAt(c) => f(c).flatMap(gatherCommutative(_, f))
5651 case other => other :: Nil
5752 }
5853
5954 /** Orders a set of commutative operations by their hash code. */
60- protected def orderCommutative (
55+ private def orderCommutative (
6156 e : Expression ,
6257 f : PartialFunction [Expression , Seq [Expression ]]): Seq [Expression ] =
6358 gatherCommutative(e, f).sortBy(_.hashCode())
6459
6560 /** Rearrange expressions that are commutative or associative. */
66- protected object Reorder extends Rule [Expression ] {
67- override def apply (e : Expression ): Expression = e transformUp {
68- case a : Add => orderCommutative(a, { case Add (l, r) => Seq (l, r) }).reduce(Add )
69- case m : Multiply => orderCommutative(m, { case Multiply (l, r) => Seq (l, r) }).reduce(Multiply )
61+ private def expressionReorder (e : Expression ): Expression = e match {
62+ case a : Add => orderCommutative(a, { case Add (l, r) => Seq (l, r) }).reduce(Add )
63+ case m : Multiply => orderCommutative(m, { case Multiply (l, r) => Seq (l, r) }).reduce(Multiply )
64+
65+ case EqualTo (l, r) if l.hashCode() > r.hashCode() => EqualTo (r, l)
66+ case EqualNullSafe (l, r) if l.hashCode() > r.hashCode() => EqualNullSafe (r, l)
7067
71- case EqualTo (l, r) if l.hashCode() > r.hashCode() => EqualTo (r, l)
72- case EqualNullSafe (l, r) if l.hashCode() > r.hashCode() => EqualNullSafe (r, l)
68+ case GreaterThan (l, r) if l.hashCode() > r.hashCode() => LessThan (r, l)
69+ case LessThan (l, r) if l.hashCode() > r.hashCode() => GreaterThan (r, l)
7370
74- case GreaterThan (l, r) if l.hashCode() > r.hashCode() => LessThan (r, l)
75- case LessThan (l, r) if l.hashCode() > r.hashCode() => GreaterThan (r, l)
71+ case GreaterThanOrEqual (l, r) if l.hashCode() > r.hashCode() => LessThanOrEqual (r, l)
72+ case LessThanOrEqual (l, r) if l.hashCode() > r.hashCode() => GreaterThanOrEqual (r, l)
7673
77- case GreaterThanOrEqual (l, r) if l.hashCode() > r.hashCode() => LessThanOrEqual (r, l)
78- case LessThanOrEqual (l, r) if l.hashCode() > r.hashCode() => GreaterThanOrEqual (r, l)
79- }
74+ case _ => e
8075 }
8176}
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