fix_unseq_compaction_loss_data_bug (#3256)

fix_unseq_compaction_loss_data_bug

server/src/main/java/org/apache/iotdb/db/engine/merge/task/MergeMultiChunkTask.java

@@ -195,6 +195,16 @@ public class MergeMultiChunkTask {
     mergeLogger.logTSEnd();
   }
 
+  private String getMaxSensor(List<PartialPath> sensors) {
+    String maxSensor = sensors.get(0).getMeasurement();
+    for (int i = 1; i < sensors.size(); i++) {
+      if (maxSensor.compareTo(sensors.get(i).getMeasurement()) < 0) {
+        maxSensor = sensors.get(i).getMeasurement();
+      }
+    }
+    return maxSensor;
+  }
+
   private void pathsMergeOneFile(int seqFileIdx, IPointReader[] unseqReaders) throws IOException {
     TsFileResource currTsFile = resource.getSeqFiles().get(seqFileIdx);
     String deviceId = currMergingPaths.get(0).getDevice();
@@ -238,7 +248,7 @@ public class MergeMultiChunkTask {
       return;
     }
 
-    String lastSensor = currMergingPaths.get(currMergingPaths.size() - 1).getMeasurement();
+    String lastSensor = getMaxSensor(currMergingPaths);
     String currSensor = null;
     Map<String, List<ChunkMetadata>> measurementChunkMetadataListMap = new TreeMap<>();
     // find all sensor to merge in order, if exceed, then break
@@ -455,7 +465,6 @@ public class MergeMultiChunkTask {
       IChunkWriter chunkWriter,
       TsFileResource currFile)
       throws IOException {
-
     int unclosedChunkPoint = lastUnclosedChunkPoint;
     boolean chunkModified =
         (currMeta.getDeleteIntervalList() != null && !currMeta.getDeleteIntervalList().isEmpty());

server/src/test/java/org/apache/iotdb/db/engine/merge/MergeTaskTest.java

@@ -215,12 +215,15 @@ public class MergeTaskTest extends MergeTest {
             null,
             null,
             true);
+    long count = 0L;
     while (tsFilesReader.hasNextBatch()) {
       BatchData batchData = tsFilesReader.nextBatch();
-      for (int i = 0; i < batchData.length(); i++) {
-        assertEquals(batchData.getTimeByIndex(i) + 20000.0, batchData.getDoubleByIndex(i), 0.001);
+      for (int t = 0; t < batchData.length(); t++) {
+        assertEquals(batchData.getTimeByIndex(t) + 20000.0, batchData.getDoubleByIndex(t), 0.001);
+        count++;
       }
     }
+    assertEquals(100, count);
     tsFilesReader.close();
   }