[SPARK-5285][SQL] Removed GroupExpression in catalyst

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

@@ -156,8 +156,8 @@ class Analyzer(catalog: Catalog,
      * expressions which equal GroupBy expressions with Literal(null), if those expressions
      * are not set for this grouping set (according to the bit mask).
      */
-    private[this] def expand(g: GroupingSets): Seq[GroupExpression] = {
-      val result = new scala.collection.mutable.ArrayBuffer[GroupExpression]
+    private[this] def expand(g: GroupingSets): Seq[Seq[Expression]] = {
+      val result = new scala.collection.mutable.ArrayBuffer[Seq[Expression]]
 
       g.bitmasks.foreach { bitmask =>
         // get the non selected grouping attributes according to the bit mask
@@ -173,7 +173,7 @@ class Analyzer(catalog: Catalog,
             Literal(bitmask, IntegerType)
         })
 
-        result += GroupExpression(substitution)
+        result += substitution
       }
 
       result.toSeq

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala

@@ -285,15 +285,3 @@ abstract class UnaryExpression extends Expression with trees.UnaryNode[Expressio
   self: Product =>
 }
 
-// TODO Semantically we probably not need GroupExpression
-// All we need is holding the Seq[Expression], and ONLY used in doing the
-// expressions transformation correctly. Probably will be removed since it's
-// not like a real expressions.
-case class GroupExpression(children: Seq[Expression]) extends Expression {
-  self: Product =>
-  type EvaluatedType = Seq[Any]
-  override def eval(input: Row): EvaluatedType = ???
-  override def nullable = false
-  override def foldable = false
-  override def dataType = ???
-}

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

@@ -161,7 +161,7 @@ case class Aggregate(
  * @param child       Child operator
  */
 case class Expand(
-    projections: Seq[GroupExpression],
+    projections: Seq[Seq[Expression]],
     output: Seq[Attribute],
     child: LogicalPlan) extends UnaryNode
 

sql/core/src/main/scala/org/apache/spark/sql/execution/Expand.scala

@@ -33,7 +33,7 @@ import org.apache.spark.sql.catalyst.plans.physical.{UnknownPartitioning, Partit
  */
 @DeveloperApi
 case class Expand(
-    projections: Seq[GroupExpression],
+    projections: Seq[Seq[Expression]],
     output: Seq[Attribute],
     child: SparkPlan)
   extends UnaryNode {
@@ -48,7 +48,7 @@ case class Expand(
       // workers via closure. However we can't assume the Projection
       // is serializable because of the code gen, so we have to
       // create the projections within each of the partition processing.
-      val groups = projections.map(ee => newProjection(ee.children, child.output)).toArray
+      val groups = projections.map(newProjection(_, child.output)).toArray
 
       new Iterator[Row] {
         private[this] var result: Row = _