Github user dbtsai commented on a diff in the pull request: https://github.com/apache/spark/pull/21852#discussion_r206266243 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala --- @@ -416,6 +416,23 @@ 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 e @ CaseWhen(branches, Some(elseValue)) if { + val values = branches.map(_._2) :+ elseValue + values.tail.forall(values.head.semanticEquals) --- End diff -- I think what you suggested is the same as the implemented code in the PR, and `elseValue.deterministic` is not required since it is checked in `semanticEquals`. Being said that, the whole condition can be replaced by `branches.exists(_._2.semanticEquals(elseValue))`
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