[GitHub] [spark] wangyum commented on a change in pull request #30852: [SPARK-33847][SQL] Replace None of elseValue inside CaseWhen if all branches are FalseLiteral

[GitBox]

wangyum commented on a change in pull request #30852:
URL: https://github.com/apache/spark/pull/30852#discussion_r546997382



##########
File path: 
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/ReplaceNullWithFalseInPredicate.scala
##########
@@ -94,6 +94,7 @@ object ReplaceNullWithFalseInPredicate extends 
Rule[LogicalPlan] {
         replaceNullWithFalse(cond) -> replaceNullWithFalse(value)
       }
       val newElseValue = cw.elseValue.map(replaceNullWithFalse)
+        .orElse(if (newBranches.forall(_._2 == FalseLiteral)) 
Some(FalseLiteral) else None)

Review comment:
       ~~How about another approach, just add this to `SimplifyConditionals`? 
The logic is clear and simple:~~
   ```scala
   case cw @ CaseWhen(_, elseValue) if cw.dataType == BooleanType && 
elseValue.isEmpty =>
     cw.copy(elseValue = Some(FalseLiteral))
   ```




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