[SPARK-13840] [SQL] Split Optimizer Rule ColumnPruning to ColumnPruning and EliminateOperator

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala

@@ -71,6 +71,7 @@ abstract class Optimizer extends RuleExecutor[LogicalPlan] {
       PushPredicateThroughAggregate,
       LimitPushDown,
       ColumnPruning,
+      EliminateOperators,
       // Operator combine
       CollapseRepartition,
       CollapseProject,
@@ -315,11 +316,7 @@ object SetOperationPushDown extends Rule[LogicalPlan] with PredicateHelper {
  *   - LeftSemiJoin
  */
 object ColumnPruning extends Rule[LogicalPlan] {
-  private def sameOutput(output1: Seq[Attribute], output2: Seq[Attribute]): Boolean =
-    output1.size == output2.size &&
-      output1.zip(output2).forall(pair => pair._1.semanticEquals(pair._2))
-
-  def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+  def apply(plan: LogicalPlan): LogicalPlan = plan transformUp {
     // Prunes the unused columns from project list of Project/Aggregate/Expand
     case p @ Project(_, p2: Project) if (p2.outputSet -- p.references).nonEmpty =>
       p.copy(child = p2.copy(projectList = p2.projectList.filter(p.references.contains)))
@@ -380,12 +377,6 @@ object ColumnPruning extends Rule[LogicalPlan] {
       p.copy(child = w.copy(
         windowExpressions = w.windowExpressions.filter(p.references.contains)))
 
-    // Eliminate no-op Window
-    case w: Window if w.windowExpressions.isEmpty => w.child
-
-    // Eliminate no-op Projects
-    case p @ Project(projectList, child) if sameOutput(child.output, p.output) => child
-
     // Can't prune the columns on LeafNode
     case p @ Project(_, l: LeafNode) => p
 
@@ -409,6 +400,24 @@ object ColumnPruning extends Rule[LogicalPlan] {
     }
 }
 
+/**
+ * Eliminate no-op Project and Window.
+ *
+ * Note: this rule should be executed just after ColumnPruning.
+ */
+object EliminateOperators extends Rule[LogicalPlan] {
+  def apply(plan: LogicalPlan): LogicalPlan = plan transformUp {
+    // Eliminate no-op Projects
+    case p @ Project(projectList, child) if sameOutput(child.output, p.output) => child
+    // Eliminate no-op Window
+    case w: Window if w.windowExpressions.isEmpty => w.child
+  }
+
+  private def sameOutput(output1: Seq[Attribute], output2: Seq[Attribute]): Boolean =
+    output1.size == output2.size &&
+      output1.zip(output2).forall(pair => pair._1.semanticEquals(pair._2))
+}
+
 /**
  * Combines two adjacent [[Project]] operators into one and perform alias substitution,
  * merging the expressions into one single expression.

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ColumnPruningSuite.scala

@@ -35,6 +35,7 @@ class ColumnPruningSuite extends PlanTest {
   object Optimize extends RuleExecutor[LogicalPlan] {
     val batches = Batch("Column pruning", FixedPoint(100),
       ColumnPruning,
+      EliminateOperators,
       CollapseProject) :: Nil
   }
 
@@ -327,8 +328,8 @@ class ColumnPruningSuite extends PlanTest {
     val input2 = LocalRelation('c.int, 'd.string, 'e.double)
     val query = Project('b :: Nil,
       Union(input1 :: input2 :: Nil)).analyze
-    val expected = Project('b :: Nil,
-      Union(Project('b :: Nil, input1) :: Project('d :: Nil, input2) :: Nil)).analyze
+    val expected =
+      Union(Project('b :: Nil, input1) :: Project('d :: Nil, input2) :: Nil).analyze
     comparePlans(Optimize.execute(query), expected)
   }
 

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/CombiningLimitsSuite.scala

@@ -28,7 +28,8 @@ class CombiningLimitsSuite extends PlanTest {
   object Optimize extends RuleExecutor[LogicalPlan] {
     val batches =
       Batch("Filter Pushdown", FixedPoint(100),
-        ColumnPruning) ::
+        ColumnPruning,
+        EliminateOperators) ::
       Batch("Combine Limit", FixedPoint(10),
         CombineLimits) ::
       Batch("Constant Folding", FixedPoint(10),

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/JoinOptimizationSuite.scala

@@ -43,6 +43,7 @@ class JoinOptimizationSuite extends PlanTest {
         PushPredicateThroughGenerate,
         PushPredicateThroughAggregate,
         ColumnPruning,
+        EliminateOperators,
         CollapseProject) :: Nil
 
   }