add header

tsfile/src/main/java/org/apache/iotdb/tsfile/write/monitor/WriteStatistics.java

diff --git a/tsfile/src/main/java/org/apache/iotdb/tsfile/write/monitor/WriteStatistics.java b/tsfile/src/main/java/org/apache/iotdb/tsfile/write/monitor/WriteStatistics.java
index e50fc0e..3ba26fd 100644
--- a/tsfile/src/main/java/org/apache/iotdb/tsfile/write/monitor/WriteStatistics.java
+++ b/tsfile/src/main/java/org/apache/iotdb/tsfile/write/monitor/WriteStatistics.java
@@ -37,6 +37,8 @@
 
   public void dump(String filePath) throws IOException {
     try (BufferedWriter writer = new BufferedWriter(new FileWriter(filePath))) {
+      writer.write("measurementId, rawSize, encodedSize, compressedSize");
+      writer.newLine();
       for (Entry<String, Statistic> entry : statisticMap.entrySet()) {
         String label = entry.getKey();
         Statistic statistic = entry.getValue();