maropu commented on a change in pull request #27231: [SPARK-28478][SQL] Remove
redundant null checks
URL: https://github.com/apache/spark/pull/27231#discussion_r368782709
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
##########
@@ -483,6 +507,19 @@ object SimplifyConditionals extends Rule[LogicalPlan]
with PredicateHelper {
} else {
e.copy(branches = branches.take(i).map(branch => (branch._1,
elseValue)))
}
+
+ case e @ CaseWhen(branches, elseValue) if branches.length == 1 =>
+ // remove redundant null checks for CaseWhen with one branch
+ branches(0)._1 match {
+ case IsNotNull(child) if isRedundantNullCheck(
+ elseValue.getOrElse(Literal.create(null, child.dataType)),
+ branches(0)._2, child) => branches(0)._2
+ case IsNull(child) if isRedundantNullCheck(
+ branches(0)._2,
+ elseValue.getOrElse(Literal.create(null, child.dataType)),
+ child) => elseValue.getOrElse(Literal.create(null, child.dataType))
+ case _ => e
+ }
Review comment:
How about this?
```
// remove redundant null checks for CaseWhen with one branch
case CaseWhen(Seq((IsNotNull(child), trueValue)), Some(falseValue))
if isRedundantNullCheck(falseValue, trueValue, child) => trueValue
case CaseWhen(Seq((IsNull(child), trueValue)), Some(falseValue))
if isRedundantNullCheck(trueValue, falseValue, child) => falseValue
case CaseWhen(Seq((IsNotNull(child), trueValue)), None)
if isRedundantNullCheck(Literal.create(null, child.dataType),
trueValue, child) => trueValue
case e @ CaseWhen(Seq((IsNull(child), trueValue)), None) =>
val nullValue = Literal.create(null, child.dataType)
if (isRedundantNullCheck(trueValue, nullValue, child)) {
nullValue
} else {
e
}
```
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