From 16b5c906ff6d38e333a20e4f5cb4244c49254c6b Mon Sep 17 00:00:00 2001
From: Reynold Xin <rxin@databricks.com>
Date: Wed, 15 Jul 2015 16:56:05 -0700
Subject: [PATCH 1/5] [SPARK-9085][SQL] Remove LeafNode, UnaryNode, BinaryNode
 from TreeNode.

---
 .../sql/catalyst/analysis/unresolved.scala    | 10 +++----
 .../catalyst/expressions/BoundAttribute.scala |  2 +-
 .../sql/catalyst/expressions/SortOrder.scala  |  3 +-
 .../sql/catalyst/expressions/aggregates.scala | 29 +++++++++----------
 .../sql/catalyst/expressions/generators.scala |  8 ++---
 .../expressions/namedExpressions.scala        | 16 +++++-----
 .../catalyst/plans/logical/LogicalPlan.scala  | 10 +++++--
 .../spark/sql/catalyst/trees/TreeNode.scala   | 16 ----------
 .../spark/sql/execution/SparkPlan.scala       | 11 +++++--
 9 files changed, 50 insertions(+), 55 deletions(-)

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/unresolved.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/unresolved.scala
index f2e579afe833..7089f079b6dd 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/unresolved.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/unresolved.scala
@@ -50,8 +50,7 @@ case class UnresolvedRelation(
 /**
  * Holds the name of an attribute that has yet to be resolved.
  */
-case class UnresolvedAttribute(nameParts: Seq[String])
-  extends Attribute with trees.LeafNode[Expression] {
+case class UnresolvedAttribute(nameParts: Seq[String]) extends Attribute {
 
   def name: String =
     nameParts.map(n => if (n.contains(".")) s"`$n`" else n).mkString(".")
@@ -96,7 +95,7 @@ case class UnresolvedFunction(name: String, children: Seq[Expression]) extends E
  * Represents all of the input attributes to a given relational operator, for example in
  * "SELECT * FROM ...". A [[Star]] gets automatically expanded during analysis.
  */
-trait Star extends NamedExpression with trees.LeafNode[Expression] {
+abstract class Star extends LeafExpression with NamedExpression {
   self: Product =>
 
   override def name: String = throw new UnresolvedException(this, "name")
@@ -151,7 +150,7 @@ case class UnresolvedStar(table: Option[String]) extends Star {
  * @param names the names to be associated with each output of computing [[child]].
  */
 case class MultiAlias(child: Expression, names: Seq[String])
-  extends NamedExpression with trees.UnaryNode[Expression] {
+  extends UnaryExpression with NamedExpression {
 
   override def name: String = throw new UnresolvedException(this, "name")
 
@@ -210,8 +209,7 @@ case class UnresolvedExtractValue(child: Expression, extraction: Expression)
 /**
  * Holds the expression that has yet to be aliased.
  */
-case class UnresolvedAlias(child: Expression) extends NamedExpression
-  with trees.UnaryNode[Expression] {
+case class UnresolvedAlias(child: Expression) extends UnaryExpression with NamedExpression {
 
   override def toAttribute: Attribute = throw new UnresolvedException(this, "toAttribute")
   override def qualifiers: Seq[String] = throw new UnresolvedException(this, "qualifiers")
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/BoundAttribute.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/BoundAttribute.scala
index 3f0d7b803125..b09aea03318d 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/BoundAttribute.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/BoundAttribute.scala
@@ -30,7 +30,7 @@ import org.apache.spark.sql.types._
  * the layout of intermediate tuples, BindReferences should be run after all such transformations.
  */
 case class BoundReference(ordinal: Int, dataType: DataType, nullable: Boolean)
-  extends NamedExpression with trees.LeafNode[Expression] {
+  extends LeafExpression with NamedExpression {
 
   override def toString: String = s"input[$ordinal]"
 
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/SortOrder.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/SortOrder.scala
index 8ab4ef060b68..6a8ee16b5954 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/SortOrder.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/SortOrder.scala
@@ -30,8 +30,7 @@ case object Descending extends SortDirection
  * An expression that can be used to sort a tuple.  This class extends expression primarily so that
  * transformations over expression will descend into its child.
  */
-case class SortOrder(child: Expression, direction: SortDirection) extends Expression
-    with trees.UnaryNode[Expression] {
+case class SortOrder(child: Expression, direction: SortDirection) extends UnaryExpression {
 
   override def dataType: DataType = child.dataType
   override def nullable: Boolean = child.nullable
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregates.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregates.scala
index c0e17f97e9b3..19d74e527084 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregates.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregates.scala
@@ -27,7 +27,7 @@ import org.apache.spark.sql.catalyst.util.TypeUtils
 import org.apache.spark.sql.types._
 import org.apache.spark.util.collection.OpenHashSet
 
-abstract class AggregateExpression extends Expression {
+trait AggregateExpression extends Expression {
   self: Product =>
 
   /**
@@ -60,7 +60,7 @@ case class SplitEvaluation(
  * An [[AggregateExpression]] that can be partially computed without seeing all relevant tuples.
  * These partial evaluations can then be combined to compute the actual answer.
  */
-abstract class PartialAggregate extends AggregateExpression {
+trait PartialAggregate extends AggregateExpression {
   self: Product =>
 
   /**
@@ -74,7 +74,7 @@ abstract class PartialAggregate extends AggregateExpression {
  * [[AggregateExpression]] with an algorithm that will be used to compute one specific result.
  */
 abstract class AggregateFunction
-  extends AggregateExpression with Serializable with trees.LeafNode[Expression] {
+  extends LeafExpression with AggregateExpression with Serializable {
   self: Product =>
 
   /** Base should return the generic aggregate expression that this function is computing */
@@ -91,7 +91,7 @@ abstract class AggregateFunction
   }
 }
 
-case class Min(child: Expression) extends PartialAggregate with trees.UnaryNode[Expression] {
+case class Min(child: Expression) extends UnaryExpression with PartialAggregate {
 
   override def nullable: Boolean = true
   override def dataType: DataType = child.dataType
@@ -124,7 +124,7 @@ case class MinFunction(expr: Expression, base: AggregateExpression) extends Aggr
   override def eval(input: InternalRow): Any = currentMin.value
 }
 
-case class Max(child: Expression) extends PartialAggregate with trees.UnaryNode[Expression] {
+case class Max(child: Expression) extends UnaryExpression with PartialAggregate {
 
   override def nullable: Boolean = true
   override def dataType: DataType = child.dataType
@@ -157,7 +157,7 @@ case class MaxFunction(expr: Expression, base: AggregateExpression) extends Aggr
   override def eval(input: InternalRow): Any = currentMax.value
 }
 
-case class Count(child: Expression) extends PartialAggregate with trees.UnaryNode[Expression] {
+case class Count(child: Expression) extends UnaryExpression with PartialAggregate {
 
   override def nullable: Boolean = false
   override def dataType: LongType.type = LongType
@@ -310,7 +310,7 @@ private[sql] case object HyperLogLogUDT extends UserDefinedType[HyperLogLog] {
 }
 
 case class ApproxCountDistinctPartition(child: Expression, relativeSD: Double)
-  extends AggregateExpression with trees.UnaryNode[Expression] {
+  extends UnaryExpression with AggregateExpression {
 
   override def nullable: Boolean = false
   override def dataType: DataType = HyperLogLogUDT
@@ -340,7 +340,7 @@ case class ApproxCountDistinctPartitionFunction(
 }
 
 case class ApproxCountDistinctMerge(child: Expression, relativeSD: Double)
-  extends AggregateExpression with trees.UnaryNode[Expression] {
+  extends UnaryExpression with AggregateExpression {
 
   override def nullable: Boolean = false
   override def dataType: LongType.type = LongType
@@ -368,7 +368,7 @@ case class ApproxCountDistinctMergeFunction(
 }
 
 case class ApproxCountDistinct(child: Expression, relativeSD: Double = 0.05)
-  extends PartialAggregate with trees.UnaryNode[Expression] {
+  extends UnaryExpression with PartialAggregate {
 
   override def nullable: Boolean = false
   override def dataType: LongType.type = LongType
@@ -386,7 +386,7 @@ case class ApproxCountDistinct(child: Expression, relativeSD: Double = 0.05)
   override def newInstance(): CountDistinctFunction = new CountDistinctFunction(child :: Nil, this)
 }
 
-case class Average(child: Expression) extends PartialAggregate with trees.UnaryNode[Expression] {
+case class Average(child: Expression) extends UnaryExpression with PartialAggregate {
 
   override def prettyName: String = "avg"
 
@@ -479,7 +479,7 @@ case class AverageFunction(expr: Expression, base: AggregateExpression)
   }
 }
 
-case class Sum(child: Expression) extends PartialAggregate with trees.UnaryNode[Expression] {
+case class Sum(child: Expression) extends UnaryExpression with PartialAggregate {
 
   override def nullable: Boolean = true
 
@@ -606,8 +606,7 @@ case class CombineSumFunction(expr: Expression, base: AggregateExpression)
   }
 }
 
-case class SumDistinct(child: Expression)
-  extends PartialAggregate with trees.UnaryNode[Expression] {
+case class SumDistinct(child: Expression) extends UnaryExpression with PartialAggregate {
 
   def this() = this(null)
   override def nullable: Boolean = true
@@ -701,7 +700,7 @@ case class CombineSetsAndSumFunction(
   }
 }
 
-case class First(child: Expression) extends PartialAggregate with trees.UnaryNode[Expression] {
+case class First(child: Expression) extends UnaryExpression with PartialAggregate {
   override def nullable: Boolean = true
   override def dataType: DataType = child.dataType
   override def toString: String = s"FIRST($child)"
@@ -729,7 +728,7 @@ case class FirstFunction(expr: Expression, base: AggregateExpression) extends Ag
   override def eval(input: InternalRow): Any = result
 }
 
-case class Last(child: Expression) extends PartialAggregate with trees.UnaryNode[Expression] {
+case class Last(child: Expression) extends UnaryExpression with PartialAggregate {
   override def references: AttributeSet = child.references
   override def nullable: Boolean = true
   override def dataType: DataType = child.dataType
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
index b68d30a26abd..05c695be4393 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
@@ -40,8 +40,7 @@ import org.apache.spark.sql.types._
  * requested.  The attributes produced by this function will be automatically copied anytime rules
  * result in changes to the Generator or its children.
  */
-abstract class Generator extends Expression {
-  self: Product =>
+trait Generator extends Expression { self: Product =>
 
   // TODO ideally we should return the type of ArrayType(StructType),
   // however, we don't keep the output field names in the Generator.
@@ -99,8 +98,9 @@ case class UserDefinedGenerator(
 /**
  * Given an input array produces a sequence of rows for each value in the array.
  */
-case class Explode(child: Expression)
-  extends Generator with trees.UnaryNode[Expression] {
+case class Explode(child: Expression) extends UnaryExpression with Generator {
+
+  override def children: Seq[Expression] = child :: Nil
 
   override def checkInputDataTypes(): TypeCheckResult = {
     if (child.dataType.isInstanceOf[ArrayType] || child.dataType.isInstanceOf[MapType]) {
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala
index 6181c60c0e45..718f291173c9 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala
@@ -37,8 +37,10 @@ object NamedExpression {
  */
 case class ExprId(id: Long)
 
-abstract class NamedExpression extends Expression {
-  self: Product =>
+/**
+ * An [[Expression]] that is named.
+ */
+trait NamedExpression extends Expression { self: Product =>
 
   def name: String
   def exprId: ExprId
@@ -78,8 +80,7 @@ abstract class NamedExpression extends Expression {
     }
 }
 
-abstract class Attribute extends NamedExpression {
-  self: Product =>
+abstract class Attribute extends LeafExpression with NamedExpression { self: Product =>
 
   override def references: AttributeSet = AttributeSet(this)
 
@@ -110,7 +111,7 @@ case class Alias(child: Expression, name: String)(
     val exprId: ExprId = NamedExpression.newExprId,
     val qualifiers: Seq[String] = Nil,
     val explicitMetadata: Option[Metadata] = None)
-  extends NamedExpression with trees.UnaryNode[Expression] {
+  extends UnaryExpression with NamedExpression {
 
   // Alias(Generator, xx) need to be transformed into Generate(generator, ...)
   override lazy val resolved =
@@ -172,7 +173,8 @@ case class AttributeReference(
     nullable: Boolean = true,
     override val metadata: Metadata = Metadata.empty)(
     val exprId: ExprId = NamedExpression.newExprId,
-    val qualifiers: Seq[String] = Nil) extends Attribute with trees.LeafNode[Expression] {
+    val qualifiers: Seq[String] = Nil)
+  extends Attribute {
 
   /**
    * Returns true iff the expression id is the same for both attributes.
@@ -242,7 +244,7 @@ case class AttributeReference(
  * A place holder used when printing expressions without debugging information such as the
  * expression id or the unresolved indicator.
  */
-case class PrettyAttribute(name: String) extends Attribute with trees.LeafNode[Expression] {
+case class PrettyAttribute(name: String) extends Attribute {
 
   override def toString: String = name
 
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala
index d7077a0ec907..f8a1f12c352f 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala
@@ -277,15 +277,21 @@ abstract class LogicalPlan extends QueryPlan[LogicalPlan] with Logging {
 /**
  * A logical plan node with no children.
  */
-abstract class LeafNode extends LogicalPlan with trees.LeafNode[LogicalPlan] {
+abstract class LeafNode extends LogicalPlan {
   self: Product =>
+
+  override def children: Seq[LogicalPlan] = Nil
 }
 
 /**
  * A logical plan node with single child.
  */
-abstract class UnaryNode extends LogicalPlan with trees.UnaryNode[LogicalPlan] {
+abstract class UnaryNode extends LogicalPlan {
   self: Product =>
+
+  def child: LogicalPlan
+
+  override def children: Seq[LogicalPlan] = child :: Nil
 }
 
 /**
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/trees/TreeNode.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/trees/TreeNode.scala
index 16844b2f4b68..0f95ca688a7a 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/trees/TreeNode.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/trees/TreeNode.scala
@@ -452,19 +452,3 @@ abstract class TreeNode[BaseType <: TreeNode[BaseType]] {
     s"$nodeName(${args.mkString(",")})"
   }
 }
-
-
-/**
- * A [[TreeNode]] with no children.
- */
-trait LeafNode[BaseType <: TreeNode[BaseType]] {
-  def children: Seq[BaseType] = Nil
-}
-
-/**
- * A [[TreeNode]] with a single [[child]].
- */
-trait UnaryNode[BaseType <: TreeNode[BaseType]] {
-  def child: BaseType
-  def children: Seq[BaseType] = child :: Nil
-}
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala
index 9dc7879fa4a1..2ebce9d1c5c3 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala
@@ -238,12 +238,19 @@ abstract class SparkPlan extends QueryPlan[SparkPlan] with Logging with Serializ
   }
 }
 
-private[sql] trait LeafNode extends SparkPlan with trees.LeafNode[SparkPlan] {
+private[sql] trait LeafNode extends SparkPlan {
   self: Product =>
+
+  override def children: Seq[SparkPlan] = Nil
 }
 
-private[sql] trait UnaryNode extends SparkPlan with trees.UnaryNode[SparkPlan] {
+private[sql] trait UnaryNode extends SparkPlan {
   self: Product =>
+
+  def child: SparkPlan
+
+  override def children: Seq[SparkPlan] = child :: Nil
+
   override def outputPartitioning: Partitioning = child.outputPartitioning
 }
 

From 2225331ea36e4a39f097e53afead6930e3cb0ed5 Mon Sep 17 00:00:00 2001
From: Reynold Xin <rxin@databricks.com>
Date: Wed, 15 Jul 2015 18:19:08 -0700
Subject: [PATCH 2/5] Aggregate expressions should not be foldable.

---
 .../spark/sql/catalyst/expressions/Expression.scala       | 1 -
 .../spark/sql/catalyst/expressions/aggregates.scala       | 6 +++++-
 .../apache/spark/sql/catalyst/optimizer/Optimizer.scala   | 4 ++--
 .../spark/sql/catalyst/plans/logical/LogicalPlan.scala    | 1 -
 .../scala/org/apache/spark/sql/execution/SparkPlan.scala  | 8 ++++----
 5 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
index 87667316aca6..d60fcb989a20 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
@@ -20,7 +20,6 @@ package org.apache.spark.sql.catalyst.expressions
 import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.analysis.{TypeCheckResult, UnresolvedAttribute}
 import org.apache.spark.sql.catalyst.expressions.codegen.{CodeGenContext, GeneratedExpressionCode}
-import org.apache.spark.sql.catalyst.trees
 import org.apache.spark.sql.catalyst.trees.TreeNode
 import org.apache.spark.sql.types._
 
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregates.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregates.scala
index 19d74e527084..71c943dc79e9 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregates.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregates.scala
@@ -20,7 +20,6 @@ package org.apache.spark.sql.catalyst.expressions
 import com.clearspring.analytics.stream.cardinality.HyperLogLog
 
 import org.apache.spark.sql.catalyst.InternalRow
-import org.apache.spark.sql.catalyst.trees
 import org.apache.spark.sql.catalyst.errors.TreeNodeException
 import org.apache.spark.sql.catalyst.analysis.TypeCheckResult
 import org.apache.spark.sql.catalyst.util.TypeUtils
@@ -30,6 +29,11 @@ import org.apache.spark.util.collection.OpenHashSet
 trait AggregateExpression extends Expression {
   self: Product =>
 
+  /**
+   * Aggregate expressions should not be foldable.
+   */
+  override def foldable: Boolean = false
+
   /**
    * Creates a new instance that can be used to compute this aggregate expression for a group
    * of input rows/
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
index 5d80214abf14..2f94b457f4cd 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
@@ -342,7 +342,7 @@ object ConstantFolding extends Rule[LogicalPlan] {
       case l: Literal => l
 
       // Fold expressions that are foldable.
-      case e if e.foldable => Literal.create(e.eval(null), e.dataType)
+      case e if e.foldable => Literal.create(e.eval(EmptyRow), e.dataType)
 
       // Fold "literal in (item1, item2, ..., literal, ...)" into true directly.
       case In(Literal(v, _), list) if list.exists {
@@ -361,7 +361,7 @@ object OptimizeIn extends Rule[LogicalPlan] {
   def apply(plan: LogicalPlan): LogicalPlan = plan transform {
     case q: LogicalPlan => q transformExpressionsDown {
       case In(v, list) if !list.exists(!_.isInstanceOf[Literal]) =>
-        val hSet = list.map(e => e.eval(null))
+        val hSet = list.map(e => e.eval(EmptyRow))
         InSet(v, HashSet() ++ hSet)
     }
   }
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala
index f8a1f12c352f..adac37231cc4 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala
@@ -23,7 +23,6 @@ import org.apache.spark.sql.catalyst.analysis._
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.plans.QueryPlan
 import org.apache.spark.sql.catalyst.trees.TreeNode
-import org.apache.spark.sql.catalyst.trees
 
 
 abstract class LogicalPlan extends QueryPlan[LogicalPlan] with Logging {
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala
index 2ebce9d1c5c3..632f633d82a2 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala
@@ -17,20 +17,20 @@
 
 package org.apache.spark.sql.execution
 
-import org.apache.spark.annotation.DeveloperApi
+import scala.collection.mutable.ArrayBuffer
+
 import org.apache.spark.Logging
+import org.apache.spark.annotation.DeveloperApi
 import org.apache.spark.rdd.{RDD, RDDOperationScope}
 import org.apache.spark.sql.SQLContext
 import org.apache.spark.sql.catalyst.InternalRow
-import org.apache.spark.sql.catalyst.{CatalystTypeConverters, trees}
+import org.apache.spark.sql.catalyst.CatalystTypeConverters
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.Row
 import org.apache.spark.sql.catalyst.expressions.codegen._
 import org.apache.spark.sql.catalyst.plans.QueryPlan
 import org.apache.spark.sql.catalyst.plans.physical._
 
-import scala.collection.mutable.ArrayBuffer
-
 object SparkPlan {
   protected[sql] val currentContext = new ThreadLocal[SQLContext]()
 }

From 9c589cf216ff5eb46031ed332a35e6e23d91d2fe Mon Sep 17 00:00:00 2001
From: Reynold Xin <rxin@databricks.com>
Date: Wed, 15 Jul 2015 19:01:47 -0700
Subject: [PATCH 3/5] Fixed one more test case...

---
 .../spark/sql/catalyst/expressions/namedExpressions.scala      | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala
index 718f291173c9..8bf7a7ce4e64 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala
@@ -42,6 +42,9 @@ case class ExprId(id: Long)
  */
 trait NamedExpression extends Expression { self: Product =>
 
+  /** We should never fold named expressions in order to not remove the alias. */
+  override def foldable: Boolean = false
+
   def name: String
   def exprId: ExprId
 

From 3135a8b9edaf52aba17c9028f1672334e793456d Mon Sep 17 00:00:00 2001
From: Reynold Xin <rxin@databricks.com>
Date: Wed, 15 Jul 2015 19:12:07 -0700
Subject: [PATCH 4/5] SortOrder should not be foldable.

---
 .../org/apache/spark/sql/catalyst/expressions/SortOrder.scala  | 3 +++
 .../org/apache/spark/sql/catalyst/expressions/generators.scala | 2 --
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/SortOrder.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/SortOrder.scala
index 6a8ee16b5954..b8f7068c9e5e 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/SortOrder.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/SortOrder.scala
@@ -32,6 +32,9 @@ case object Descending extends SortDirection
  */
 case class SortOrder(child: Expression, direction: SortDirection) extends UnaryExpression {
 
+  /** Sort order is not foldable because we don't have an eval for it. */
+  override def foldable: Boolean = false
+
   override def dataType: DataType = child.dataType
   override def nullable: Boolean = child.nullable
 
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
index 05c695be4393..a35b3cebf7f7 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
@@ -127,6 +127,4 @@ case class Explode(child: Expression) extends UnaryExpression with Generator {
         else inputMap.map { case (k, v) => InternalRow(k, v) }
     }
   }
-
-  override def toString: String = s"explode($child)"
 }

From 9e8a4def6f02e03899fa2fafdd2841c513d280af Mon Sep 17 00:00:00 2001
From: Reynold Xin <rxin@databricks.com>
Date: Wed, 15 Jul 2015 21:03:20 -0700
Subject: [PATCH 5/5] Generator should not be foldable.

---
 .../org/apache/spark/sql/catalyst/expressions/generators.scala  | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
index a35b3cebf7f7..51dc77ee3fc5 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
@@ -46,6 +46,8 @@ trait Generator extends Expression { self: Product =>
   // however, we don't keep the output field names in the Generator.
   override def dataType: DataType = throw new UnsupportedOperationException
 
+  override def foldable: Boolean = false
+
   override def nullable: Boolean = false
 
   /**