fix build

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala

@@ -257,7 +257,7 @@ abstract class LogicalPlan extends QueryPlan[LogicalPlan] with Logging {
 
       // More than one match.
       case ambiguousReferences =>
-        val qualifiers = ambiguousReferences.flatMap(_._1.qualifiers)
+        val qualifiers = ambiguousReferences.flatMap(_._1.qualifier)
         if (qualifiers.nonEmpty && qualifiers.distinct.length == qualifiers.length) {
           throw new AnalysisException(s"Reference '$name' is ambiguous, please add a qualifier " +
             s"to distinguish it, e.g. '${qualifiers.head}.$name', available qualifiers: " +

sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala

@@ -314,7 +314,7 @@ class Dataset[T] private[sql](
         s"New column names (${colNames.size}): " + colNames.mkString(", "))
 
     val newCols = logicalPlan.output.zip(colNames).map { case (oldAttribute, newName) =>
-      Column(Alias(oldAttribute, newName)(qualifiers = oldAttribute.qualifiers))
+      Column(Alias(oldAttribute, newName)(qualifier = oldAttribute.qualifier))
     }
     select(newCols : _*)
   }
@@ -769,7 +769,7 @@ class Dataset[T] private[sql](
       Column(ResolvedStar(queryExecution.analyzed.output))
     case _ =>
       val col = resolve(colName) match {
-        case attr: Attribute => UnresolvedAttribute(attr.qualifiers :+ attr.name)
+        case attr: Attribute => UnresolvedAttribute(attr.qualifier.toSeq :+ attr.name)
         case Alias(child, _) => UnresolvedAttribute.quotedString(child.sql)
       }
       Column(col)
@@ -1585,7 +1585,7 @@ class Dataset[T] private[sql](
     if (shouldRename) {
       val columns = output.map { col =>
         if (resolver(col.name, existingName)) {
-          Column(Alias(col, newName)(qualifiers = col.qualifiers))
+          Column(Alias(col, newName)(qualifier = col.qualifier))
         } else {
           Column(col)
         }

sql/core/src/test/scala/org/apache/spark/sql/execution/PlannerSuite.scala

@@ -169,7 +169,7 @@ class PlannerSuite extends SharedSQLContext {
     val planned = query.queryExecution.executedPlan
     assert(planned.isInstanceOf[execution.TakeOrderedAndProject])
     assert(planned.output ===
-      testData.select('key, 'value).logicalPlan.output.map(_.withQualifiers(Nil)))
+      testData.select('key, 'value).logicalPlan.output.map(_.withQualifier(None)))
   }
 
   test("terminal limit -> project -> sort should use TakeOrderedAndProject") {