[SPARK-10743][SQL] keep the name of expression if possible when do cast

Author: Wenchen Fan <cloud0fan@163.com>

Closes #8859 from cloud-fan/cast.

1 files changed, 16 insertions, 17 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
index 9237f2f3dd..016dc293f4 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
@@ -141,32 +141,31 @@ class Analyzer(
    */
   object ResolveAliases extends Rule[LogicalPlan] {
     private def assignAliases(exprs: Seq[NamedExpression]) = {
-      // The `UnresolvedAlias`s will appear only at root of a expression tree, we don't need
-      // to traverse the whole tree.
       exprs.zipWithIndex.map {
-        case (u @ UnresolvedAlias(child), i) =>
-          child match {
-            case _: UnresolvedAttribute => u
-            case ne: NamedExpression => ne
-            case g: Generator if g.resolved && g.elementTypes.size > 1 => MultiAlias(g, Nil)
-            case e if !e.resolved => u
-            case other => Alias(other, s"_c$i")()
+        case (expr, i) =>
+          expr transform {
+            case u @ UnresolvedAlias(child) => child match {
+              case ne: NamedExpression => ne
+              case e if !e.resolved => u
+              case g: Generator if g.elementTypes.size > 1 => MultiAlias(g, Nil)
+              case c @ Cast(ne: NamedExpression, _) => Alias(c, ne.name)()
+              case other => Alias(other, s"_c$i")()
+            }
           }
-        case (other, _) => other
-      }
+      }.asInstanceOf[Seq[NamedExpression]]
     }
 
+    private def hasUnresolvedAlias(exprs: Seq[NamedExpression]) =
+      exprs.exists(_.find(_.isInstanceOf[UnresolvedAlias]).isDefined)
+
     def apply(plan: LogicalPlan): LogicalPlan = plan resolveOperators {
-      case Aggregate(groups, aggs, child)
-        if child.resolved && aggs.exists(_.isInstanceOf[UnresolvedAlias]) =>
+      case Aggregate(groups, aggs, child) if child.resolved && hasUnresolvedAlias(aggs) =>
         Aggregate(groups, assignAliases(aggs), child)
 
-      case g: GroupingAnalytics
-        if g.child.resolved && g.aggregations.exists(_.isInstanceOf[UnresolvedAlias]) =>
+      case g: GroupingAnalytics if g.child.resolved && hasUnresolvedAlias(g.aggregations) =>
         g.withNewAggs(assignAliases(g.aggregations))
 
-      case Project(projectList, child)
-        if child.resolved && projectList.exists(_.isInstanceOf[UnresolvedAlias]) =>
+      case Project(projectList, child) if child.resolved && hasUnresolvedAlias(projectList) =>
         Project(assignAliases(projectList), child)
     }
   }