cloud-fan commented on a change in pull request #30852:
URL: https://github.com/apache/spark/pull/30852#discussion_r547394139
##########
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:
Here we do need the logic from 2 optimizer rules:
1. null means false in predicates
2. eliminate CASE WHEN if all branches return the same value
We can probably include logic 2 in this rule
```
...
if (newBranches.forall(_._2 == FalseLiteral) && cw.elseValue.isEmpty) {
FalseLiteral
} else {
val newElseValue = cw.elseValue.map(replaceNullWithFalse)
CaseWhen(newBranches, newElseValue)
}
```
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