[SPARK-12989] [SQL] Delaying Alias Cleanup after ExtractWindowExpressions

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala

@@ -883,12 +883,13 @@ class Analyzer(
           if (missingExpr.nonEmpty) {
             extractedExprBuffer += ne
           }
-          ne.toAttribute
+          // alias will be cleaned in the rule CleanupAliases
+          ne
         case e: Expression if e.foldable =>
           e // No need to create an attribute reference if it will be evaluated as a Literal.
         case e: Expression =>
           // For other expressions, we extract it and replace it with an AttributeReference (with
-          // an interal column name, e.g. "_w0").
+          // an internal column name, e.g. "_w0").
           val withName = Alias(e, s"_w${extractedExprBuffer.length}")()
           extractedExprBuffer += withName
           withName.toAttribute

sql/core/src/test/scala/org/apache/spark/sql/DataFrameWindowSuite.scala

@@ -344,4 +344,14 @@ class DataFrameWindowSuite extends QueryTest with SharedSQLContext {
         Row("b", 1, null, null, null, null, null, null),
         Row("b", 2, null, null, null, null, null, null)))
   }
+
+  test("SPARK-12989 ExtractWindowExpressions treats alias as regular attribute") {
+    val src = Seq((0, 3, 5)).toDF("a", "b", "c")
+      .withColumn("Data", struct("a", "b"))
+      .drop("a")
+      .drop("b")
+    val winSpec = Window.partitionBy("Data.a", "Data.b").orderBy($"c".desc)
+    val df = src.select($"*", max("c").over(winSpec) as "max")
+    checkAnswer(df, Row(5, Row(0, 3), 5))
+  }
 }