Github user yhuai commented on a diff in the pull request:
https://github.com/apache/spark/pull/10781#discussion_r49961357
--- Diff: sql/core/src/main/scala/org/apache/spark/sql/Column.scala ---
@@ -133,6 +133,15 @@ class Column(protected[sql] val expr: Expression)
extends Logging {
case func: UnresolvedFunction => UnresolvedAlias(func,
Some(func.prettyString))
+ // If we have a top level Cast, there is a chance to give it a better
alias, if there is a
+ // NamedExpression under this Cast.
+ case c: Cast => c.transformUp {
+ case Cast(ne: NamedExpression, to) => UnresolvedAlias(Cast(ne, to))
+ } match {
+ case ne: NamedExpression => ne
+ case other => Alias(expr, expr.prettyString)()
+ }
--- End diff --
oh, i see. It will be good to propagate the name to the top level. The
current change can do the job, right?
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