Github user dbtsai commented on a diff in the pull request:
https://github.com/apache/spark/pull/21850#discussion_r205556780
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
---
@@ -414,6 +414,9 @@ object SimplifyConditionals extends Rule[LogicalPlan]
with PredicateHelper {
// these branches can be pruned away
val (h, t) = branches.span(_._1 != TrueLiteral)
CaseWhen( h :+ t.head, None)
+
+ case CaseWhen(Seq((cond, trueValue)), elseValue) =>
+ If(cond, trueValue, elseValue.getOrElse(Literal(null,
trueValue.dataType)))
--- End diff --
The generated Java code is slightly simpler, but I agree there should not
have any performance gain. Being said that, once `CaseWhen` is converted into
`If`, this condition expression will be benefited from the optimization rules
in `If` which may not be implemented for `CaseWhen` case.
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