[SPARK-9729] [SPARK-9363] [SQL] Use sort merge join for left and right outer join

This patch adds a new `SortMergeOuterJoin` operator that performs left and right outer joins using sort merge join.  It also refactors `SortMergeJoin` in order to improve performance and code clarity.

Along the way, I also performed a couple pieces of minor cleanup and optimization:

- Rename the `HashJoin` physical planner rule to `EquiJoinSelection`, since it's also used for non-hash joins.
- Rewrite the comment at the top of `HashJoin` to better explain the precedence for choosing join operators.
- Update `JoinSuite` to use `SqlTestUtils.withConf` for changing SQLConf settings.

This patch incorporates several ideas from adrian-wang's patch, #5717.

Closes #5717.

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/apache/spark/7904)
<!-- Reviewable:end -->

Author: Josh Rosen <joshrosen@databricks.com>
Author: Daoyuan Wang <daoyuan.wang@intel.com>

Closes #7904 from JoshRosen/outer-join-smj and squashes 1 commits.

1 files changed, 3 insertions, 3 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/JoinedRow.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/JoinedRow.scala
index b76757c935..d3560df079 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/JoinedRow.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/JoinedRow.scala
@@ -37,20 +37,20 @@ class JoinedRow extends InternalRow {
   }
 
   /** Updates this JoinedRow to used point at two new base rows.  Returns itself. */
-  def apply(r1: InternalRow, r2: InternalRow): InternalRow = {
+  def apply(r1: InternalRow, r2: InternalRow): JoinedRow = {
     row1 = r1
     row2 = r2
     this
   }
 
   /** Updates this JoinedRow by updating its left base row.  Returns itself. */
-  def withLeft(newLeft: InternalRow): InternalRow = {
+  def withLeft(newLeft: InternalRow): JoinedRow = {
     row1 = newLeft
     this
   }
 
   /** Updates this JoinedRow by updating its right base row.  Returns itself. */
-  def withRight(newRight: InternalRow): InternalRow = {
+  def withRight(newRight: InternalRow): JoinedRow = {
     row2 = newRight
     this
   }