[GitHub] [spark] cloud-fan commented on a change in pull request #30222: [SPARK-33315][SQL] Simplify CaseWhen with EqualTo

[GitBox <gi...@apache.org>]

cloud-fan commented on a change in pull request #30222:
URL: https://github.com/apache/spark/pull/30222#discussion_r542199756



##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
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@@ -523,6 +523,16 @@ object SimplifyConditionals extends Rule[LogicalPlan] with PredicateHelper {
         } else {
           e.copy(branches = branches.take(i).map(branch => (branch._1, elseValue)))
         }
+
+      case e @ EqualTo(c @ CaseWhen(branches, elseValue), right)
+          if c.deterministic &&
+            right.isInstanceOf[Literal] && branches.forall(_._2.isInstanceOf[Literal]) &&
+            elseValue.forall(_.isInstanceOf[Literal]) =>
+        if ((branches.map(_._2) ++ elseValue).forall(!_.equals(right))) {

Review comment:
       can we use an `EqualTo` expression to compare literals? and how about the null semantic?




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