Add a test case

Author: DonnyZone

sql/core/src/test/scala/org/apache/spark/sql/execution/WholeStageCodegenSuite.scala

@@ -18,10 +18,12 @@
 package org.apache.spark.sql.execution
 
 import org.apache.spark.sql.{Column, Dataset, Row}
+import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute
 import org.apache.spark.sql.catalyst.expressions.{Add, Literal, Stack}
 import org.apache.spark.sql.execution.aggregate.HashAggregateExec
 import org.apache.spark.sql.execution.joins.BroadcastHashJoinExec
+import org.apache.spark.sql.execution.joins.SortMergeJoinExec
 import org.apache.spark.sql.expressions.scalalang.typed
 import org.apache.spark.sql.functions.{avg, broadcast, col, max}
 import org.apache.spark.sql.test.SharedSQLContext