Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/990#discussion_r13558814
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -154,6 +155,10 @@ object NullPropagation extends Rule[LogicalPlan] {
case left :: Literal(null, _) :: Nil => Literal(null, e.dataType)
case _ => e
}
+ case e: CaseConversionExpression => e.children match {
--- End diff --
This case would be more generally handled by constant folding. Can you
override foldable in these expressions to be true if the child is foldable?
Also please fix the toString methods.
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