maropu commented on a change in pull request #25717: [WIP][SPARK-29013][SQL]
Structurally equivalent subexpression elimination
URL: https://github.com/apache/spark/pull/25717#discussion_r321996734
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
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@@ -40,23 +40,47 @@ class EquivalentExpressions {
override def hashCode: Int = e.semanticHash()
}
+ /**
+ * Wrapper around an Expression that provides structural semantic equality.
+ */
+ case class StructuralExpr(e: Expression) {
+ def normalized(expr: Expression): Expression = {
+ expr.transformUp {
+ case b: ParameterizedBoundReference =>
Review comment:
To avoid unnecessary plan copys, we can check this equality based on
`BoundReference` (by just copying it like `b.copy(ordinal = 0 or -1?)`)? IIUC
its ok to replace `BoundReference` with `ParameterizedBoundReference` just when
generating code in
https://github.com/apache/spark/pull/25717/files#diff-8bcc5aea39c73d4bf38aef6f6951d42cR1117?
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