Github user maropu commented on a diff in the pull request:
https://github.com/apache/spark/pull/21704#discussion_r200025173
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala
---
@@ -2007,7 +2007,14 @@ case class Concat(children: Seq[Expression]) extends
Expression {
}
}
- override def dataType: DataType =
children.map(_.dataType).headOption.getOrElse(StringType)
+ override def dataType: DataType = {
+ val dataTypes = children.map(_.dataType)
+ dataTypes.headOption.map {
+ case ArrayType(et, _) =>
+ ArrayType(et,
dataTypes.exists(_.asInstanceOf[ArrayType].containsNull))
+ case dt => dt
+ }.getOrElse(StringType)
+ }
--- End diff --
Aha, I see. But, I just have a hunch that `SimplifyCasts` cannot simplify
array casts in some cases?, e.g., this concat case. Since we basically cannot
change semantics in optimization phase, I feel a little weird about this
simplification.
Anyway, I'm ok with your approach because I can't find a better & simpler
way to solve this in analysis phase... Thanks!
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