[SPARK-21351][SQL] Remove the UpdateAttributeNullability rule from the optimizer

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/UpdateAttributeNullability.scala

@@ -29,9 +29,6 @@ import org.apache.spark.sql.catalyst.rules.Rule
  * nullable field can be actually set as non-nullable, which cause illegal optimization
  * (e.g., NULL propagation) and wrong answers.
  * See SPARK-13484 and SPARK-13801 for the concrete queries of this case.
- *
- * This rule should be executed again at the end of optimization phase, as optimizer may change
- * some expressions and their nullabilities as well. See SPARK-21351 for more details.
  */
 object UpdateAttributeNullability extends Rule[LogicalPlan] {
 

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

@@ -179,7 +179,6 @@ abstract class Optimizer(sessionCatalog: SessionCatalog)
       ColumnPruning,
       CollapseProject,
       RemoveNoopOperators) :+
-    Batch("UpdateNullability", Once, UpdateAttributeNullability) :+
     // This batch must be executed after the `RewriteSubquery` batch, which creates joins.
     Batch("NormalizeFloatingNumbers", Once, NormalizeFloatingNumbers)
   }