address comments.

Author: gatorsmile

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

@@ -950,6 +950,7 @@ object OuterJoinElimination extends Rule[LogicalPlan] with PredicateHelper {
    * Returns whether the expression returns null or false when all inputs are nulls.
    */
   private def canFilterOutNull(e: Expression): Boolean = {
+    if (!e.deterministic) return false
     val attributes = e.references.toSeq
     val emptyRow = new GenericInternalRow(attributes.length)
     val v = BindReferences.bindReference(e, attributes).eval(emptyRow)
@@ -988,7 +989,8 @@ object OuterJoinElimination extends Rule[LogicalPlan] with PredicateHelper {
 
   def apply(plan: LogicalPlan): LogicalPlan = plan transform {
     case f @ Filter(condition, j @ Join(_, _, RightOuter | LeftOuter | FullOuter, _)) =>
-      Filter(condition, buildNewJoin(f, j))
+      val newJoin = buildNewJoin(f, j)
+      if (j.joinType == newJoin.joinType) f else Filter(condition, newJoin)
   }
 }
 

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala

@@ -56,8 +56,6 @@ abstract class QueryPlan[PlanType <: TreeNode[PlanType]] extends TreeNode[PlanTy
         Set(IsNotNull(l), IsNotNull(r))
       case LessThanOrEqual(l, r) =>
         Set(IsNotNull(l), IsNotNull(r))
-      case EqualNullSafe(l, r) if !r.nullable || !l.nullable =>
-        Set(IsNotNull(l), IsNotNull(r))
       case _ =>
         Set.empty[Expression]
     }.foldLeft(Set.empty[Expression])(_ union _.toSet)

sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala

@@ -81,7 +81,7 @@ class JoinSuite extends QueryTest with SharedSQLContext {
       ("SELECT * FROM testData JOIN testData2 ON key = a where key = 2", classOf[SortMergeJoin]),
       ("SELECT * FROM testData LEFT JOIN testData2 ON key = a", classOf[SortMergeOuterJoin]),
       ("SELECT * FROM testData RIGHT JOIN testData2 ON key = a where key = 2",
-        classOf[SortMergeJoin]), // conversion from Right Outer to Inner
+        classOf[SortMergeJoin]), // converted from Right Outer to Inner
       ("SELECT * FROM testData right join testData2 ON key = a and key = 2",
         classOf[SortMergeOuterJoin]),
       ("SELECT * FROM testData full outer join testData2 ON key = a",