[SPARK-4742][SQL] The name of Parquet File generated by AppendingParquetOutputFormat should be zero padded

When I use Parquet File as a output file using ParquetOutputFormat#getDefaultWorkFile, the file name is not zero padded while RDD#saveAsText does zero padding.

Author: Sasaki Toru <sasakitoa@nttdata.co.jp>

Closes #3602 from sasakitoa/parquet-zeroPadding and squashes the following commits:

6b0e58f [Sasaki Toru] Merge branch 'master' of git://github.com/apache/spark into parquet-zeroPadding
20dc79d [Sasaki Toru] Fixed the name of Parquet File generated by AppendingParquetOutputFormat

sql/core/src/main/scala/org/apache/spark/sql/parquet/ParquetTableOperations.scala

@@ -20,6 +20,7 @@ package org.apache.spark.sql.parquet
 import java.io.IOException
 import java.lang.{Long => JLong}
 import java.text.SimpleDateFormat
+import java.text.NumberFormat
 import java.util.concurrent.{Callable, TimeUnit}
 import java.util.{ArrayList, Collections, Date, List => JList}
 
@@ -338,9 +339,13 @@ private[parquet] class AppendingParquetOutputFormat(offset: Int)
 
   // override to choose output filename so not overwrite existing ones
   override def getDefaultWorkFile(context: TaskAttemptContext, extension: String): Path = {
+    val numfmt = NumberFormat.getInstance()
+    numfmt.setMinimumIntegerDigits(5)
+    numfmt.setGroupingUsed(false)
+
     val taskId: TaskID = getTaskAttemptID(context).getTaskID
     val partition: Int = taskId.getId
-    val filename = s"part-r-${partition + offset}.parquet"
+    val filename = "part-r-" + numfmt.format(partition + offset) + ".parquet"
     val committer: FileOutputCommitter =
       getOutputCommitter(context).asInstanceOf[FileOutputCommitter]
     new Path(committer.getWorkPath, filename)