address comments

sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/HiveFileFormat.scala

@@ -29,6 +29,7 @@ import org.apache.hadoop.io.Writable
 import org.apache.hadoop.mapred.{JobConf, Reporter}
 import org.apache.hadoop.mapreduce.{Job, TaskAttemptContext}
 
+import org.apache.spark.internal.Logging
 import org.apache.spark.sql.SparkSession
 import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.execution.datasources.{FileFormat, OutputWriter, OutputWriterFactory}
@@ -42,7 +43,7 @@ import org.apache.spark.util.SerializableJobConf
  *
  * TODO: implement the read logic.
  */
-class HiveFileFormat(fileSinkConf: FileSinkDesc) extends FileFormat {
+class HiveFileFormat(fileSinkConf: FileSinkDesc) extends FileFormat with Logging {
   override def inferSchema(
       sparkSession: SparkSession,
       options: Map[String, String],
@@ -59,6 +60,19 @@ class HiveFileFormat(fileSinkConf: FileSinkDesc) extends FileFormat {
     val tableDesc = fileSinkConf.getTableInfo
     conf.set("mapred.output.format.class", tableDesc.getOutputFileFormatClassName)
 
+    // When speculation is on and output committer class name contains "Direct", we should warn
+    // users that they may loss data if they are using a direct output committer.
+    val speculationEnabled = sparkSession.sparkContext.conf.getBoolean("spark.speculation", false)
+    val outputCommitterClass = conf.get("mapred.output.committer.class", "")
+    if (speculationEnabled && outputCommitterClass.contains("Direct")) {
+      val warningMessage =
+        s"$outputCommitterClass may be an output committer that writes data directly to " +
+          "the final location. Because speculation is enabled, this output committer may " +
+          "cause data loss (see the case in SPARK-10063). If possible, please use an output " +
+          "committer that does not have this behavior (e.g. FileOutputCommitter)."
+      logWarning(warningMessage)
+    }
+
     // Add table properties from storage handler to hadoopConf, so any custom storage
     // handler settings can be set to hadoopConf
     HiveTableUtil.configureJobPropertiesForStorageHandler(tableDesc, conf, false)