LantaoJin commented on a change in pull request #31189:
URL: https://github.com/apache/spark/pull/31189#discussion_r633392269
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
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@@ -620,6 +620,37 @@ object PushFoldableIntoBranches extends Rule[LogicalPlan]
with PredicateHelper {
}
}
+/**
+ * Remove duplicated case when branches.
+ */
+object RemoveDuplicatedBranches extends Rule[LogicalPlan] with PredicateHelper
{
+
+ /**
+ * Wrapper around a branch that provides semantic equality.
+ */
+ case class EquivalentBranch(br: (Expression, Expression)) {
+ override def equals(o: Any): Boolean = o match {
+ case other: EquivalentBranch if br._1.deterministic &&
other.br._1.deterministic =>
+ br._1.semanticEquals(other.br._1)
+ case _ => false
+ }
+
+ override def hashCode: Int = br._1.semanticHash()
+ }
+
+ def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ case q: LogicalPlan => q transformExpressionsUp {
+ case c @ CaseWhen(branches, _) if branches.length > 1 =>
+ val equivalentBranchSet = branches.map(EquivalentBranch).toSet
+ if (equivalentBranchSet.size < branches.length) {
+ val dedup = equivalentBranchSet.map(_.br).toSeq
Review comment:
Good catch. Should be
```scala
val distinctEquivalentBranches =
branches.map(EquivalentBranch).distinct
if (distinctEquivalentBranches.size < branches.length) {
val dedup = distinctEquivalentBranches.map(_.br)
c.copy(branches = dedup)
} else {
c
}
```
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