add import

carsonwang · carsonwang · commit bef8ab879614 · 2019-02-28T11:04:45.000+08:00
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/adaptive/rule/ReduceNumShufflePartitions.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/adaptive/rule/ReduceNumShufflePartitions.scala
@@ -17,6 +17,7 @@
 
 package org.apache.spark.sql.execution.adaptive.rule
 
+import scala.collection.mutable.ArrayBuffer
 import scala.concurrent.duration.Duration
 
 import org.apache.spark.MapOutputStatistics
