[SQL] SPARK-1371 Hash Aggregation Improvements

Given:
```scala
case class Data(a: Int, b: Int)
val rdd =
  sparkContext
    .parallelize(1 to 200)
    .flatMap(_ => (1 to 50000).map(i => Data(i % 100, i)))
rdd.registerAsTable("data")
cacheTable("data")
```
Before:
```
SELECT COUNT(*) FROM data:[10000000]
16795.567ms
SELECT a, SUM(b) FROM data GROUP BY a
7536.436ms
SELECT SUM(b) FROM data
10954.1ms
```

After:
```
SELECT COUNT(*) FROM data:[10000000]
1372.175ms
SELECT a, SUM(b) FROM data GROUP BY a
2070.446ms
SELECT SUM(b) FROM data
958.969ms
```

Author: Michael Armbrust <michael@databricks.com>

Closes #295 from marmbrus/hashAgg and squashes the following commits:

ec63575 [Michael Armbrust] Add comment.
d0495a9 [Michael Armbrust] Use scaladoc instead.
b4a6887 [Michael Armbrust] Address review comments.
a2d90ba [Michael Armbrust] Capture child output statically to avoid issues with generators and serialization.
7c13112 [Michael Armbrust] Rewrite Aggregate operator to stream input and use projections.  Remove unused local RDD functions implicits.
5096f99 [Michael Armbrust] Make HiveUDAF fields transient since object inspectors are not serializable.
6a4b671 [Michael Armbrust] Add option to avoid binding operators expressions automatically.
92cca08 [Michael Armbrust] Always include serialization debug info when running tests.
1279df2 [Michael Armbrust] Increase default number of partitions.

3 files changed, 17 insertions, 11 deletions

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 f70e80b7f2..37b9035df9 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
@@ -48,11 +48,17 @@ case class BoundReference(ordinal: Int, baseReference: Attribute)
   override def apply(input: Row): Any = input(ordinal)
 }
 
+/**
+ * Used to denote operators that do their own binding of attributes internally.
+ */
+trait NoBind { self: trees.TreeNode[_] => }
+
 class BindReferences[TreeNode <: QueryPlan[TreeNode]] extends Rule[TreeNode] {
   import BindReferences._
 
   def apply(plan: TreeNode): TreeNode = {
     plan.transform {
+      case n: NoBind => n.asInstanceOf[TreeNode]
       case leafNode if leafNode.children.isEmpty => leafNode
       case unaryNode if unaryNode.children.size == 1 => unaryNode.transformExpressions { case e =>
         bindReference(e, unaryNode.children.head.output)
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Projection.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Projection.scala
index 38542d3fc7..5576ecbb65 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Projection.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Projection.scala
@@ -28,9 +28,9 @@ class Projection(expressions: Seq[Expression]) extends (Row => Row) {
 
   protected val exprArray = expressions.toArray
   def apply(input: Row): Row = {
-    val outputArray = new Array[Any](exprArray.size)
+    val outputArray = new Array[Any](exprArray.length)
     var i = 0
-    while (i < exprArray.size) {
+    while (i < exprArray.length) {
       outputArray(i) = exprArray(i).apply(input)
       i += 1
     }
@@ -57,7 +57,7 @@ case class MutableProjection(expressions: Seq[Expression]) extends (Row => Row)
 
   def apply(input: Row): Row = {
     var i = 0
-    while (i < exprArray.size) {
+    while (i < exprArray.length) {
       mutableRow(i) = exprArray(i).apply(input)
       i += 1
     }
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 7303b155ca..53b884a41e 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 @@ abstract class AggregateExpression extends Expression {
    * Creates a new instance that can be used to compute this aggregate expression for a group
    * of input rows/
    */
-  def newInstance: AggregateFunction
+  def newInstance(): AggregateFunction
 }
 
 /**
@@ -75,7 +75,7 @@ abstract class AggregateFunction
   override def apply(input: Row): Any
 
   // Do we really need this?
-  def newInstance = makeCopy(productIterator.map { case a: AnyRef => a }.toArray)
+  def newInstance() = makeCopy(productIterator.map { case a: AnyRef => a }.toArray)
 }
 
 case class Count(child: Expression) extends PartialAggregate with trees.UnaryNode[Expression] {
@@ -89,7 +89,7 @@ case class Count(child: Expression) extends PartialAggregate with trees.UnaryNod
     SplitEvaluation(Sum(partialCount.toAttribute), partialCount :: Nil)
   }
 
-  override def newInstance = new CountFunction(child, this)
+  override def newInstance()= new CountFunction(child, this)
 }
 
 case class CountDistinct(expressions: Seq[Expression]) extends AggregateExpression {
@@ -98,7 +98,7 @@ case class CountDistinct(expressions: Seq[Expression]) extends AggregateExpressi
   def nullable = false
   def dataType = IntegerType
   override def toString = s"COUNT(DISTINCT ${expressions.mkString(",")}})"
-  override def newInstance = new CountDistinctFunction(expressions, this)
+  override def newInstance()= new CountDistinctFunction(expressions, this)
 }
 
 case class Average(child: Expression) extends PartialAggregate with trees.UnaryNode[Expression] {
@@ -118,7 +118,7 @@ case class Average(child: Expression) extends PartialAggregate with trees.UnaryN
       partialCount :: partialSum :: Nil)
   }
 
-  override def newInstance = new AverageFunction(child, this)
+  override def newInstance()= new AverageFunction(child, this)
 }
 
 case class Sum(child: Expression) extends PartialAggregate with trees.UnaryNode[Expression] {
@@ -134,7 +134,7 @@ case class Sum(child: Expression) extends PartialAggregate with trees.UnaryNode[
       partialSum :: Nil)
   }
 
-  override def newInstance = new SumFunction(child, this)
+  override def newInstance()= new SumFunction(child, this)
 }
 
 case class SumDistinct(child: Expression)
@@ -145,7 +145,7 @@ case class SumDistinct(child: Expression)
   def dataType = child.dataType
   override def toString = s"SUM(DISTINCT $child)"
 
-  override def newInstance = new SumDistinctFunction(child, this)
+  override def newInstance()= new SumDistinctFunction(child, this)
 }
 
 case class First(child: Expression) extends PartialAggregate with trees.UnaryNode[Expression] {
@@ -160,7 +160,7 @@ case class First(child: Expression) extends PartialAggregate with trees.UnaryNod
       First(partialFirst.toAttribute),
       partialFirst :: Nil)
   }
-  override def newInstance = new FirstFunction(child, this)
+  override def newInstance()= new FirstFunction(child, this)
 }
 
 case class AverageFunction(expr: Expression, base: AggregateExpression)