@Test
  public void singleDeviceViewOperatorTest() {
    ExecutorService instanceNotificationExecutor =
        IoTDBThreadPoolFactory.newFixedThreadPool(1, "test-instance-notification");
    try {
      // construct operator tree
      QueryId queryId = new QueryId("stub_query");
      FragmentInstanceId instanceId =
          new FragmentInstanceId(new PlanFragmentId(queryId, 0), "stub-instance");
      FragmentInstanceStateMachine stateMachine =
          new FragmentInstanceStateMachine(instanceId, instanceNotificationExecutor);
      FragmentInstanceContext fragmentInstanceContext =
          createFragmentInstanceContext(instanceId, stateMachine);
      DriverContext driverContext = new DriverContext(fragmentInstanceContext, 0);

      PlanNodeId planNodeId1 = new PlanNodeId("1");
      driverContext.addOperatorContext(1, planNodeId1, SeriesScanOperator.class.getSimpleName());
      PlanNodeId planNodeId2 = new PlanNodeId("2");
      driverContext.addOperatorContext(2, planNodeId2, SeriesScanOperator.class.getSimpleName());
      driverContext.addOperatorContext(
          3, new PlanNodeId("3"), FullOuterTimeJoinOperator.class.getSimpleName());
      driverContext.addOperatorContext(
          4, new PlanNodeId("4"), SingleDeviceViewOperator.class.getSimpleName());

      NonAlignedFullPath measurementPath1 =
          new NonAlignedFullPath(
              IDeviceID.Factory.DEFAULT_FACTORY.create(
                  SINGLE_DEVICE_MERGE_OPERATOR_TEST_SG + ".device0"),
              new MeasurementSchema("sensor0", TSDataType.INT32));
      NonAlignedFullPath measurementPath2 =
          new NonAlignedFullPath(
              IDeviceID.Factory.DEFAULT_FACTORY.create(
                  SINGLE_DEVICE_MERGE_OPERATOR_TEST_SG + ".device0"),
              new MeasurementSchema("sensor1", TSDataType.INT32));

      SeriesScanOperator seriesScanOperator1 =
          new SeriesScanOperator(
              driverContext.getOperatorContexts().get(0),
              planNodeId1,
              measurementPath1,
              Ordering.ASC,
              SeriesScanOptions.getDefaultSeriesScanOptions(measurementPath1));
      seriesScanOperator1.initQueryDataSource(new QueryDataSource(seqResources, unSeqResources));
      seriesScanOperator1
          .getOperatorContext()
          .setMaxRunTime(new Duration(500, TimeUnit.MILLISECONDS));

      SeriesScanOperator seriesScanOperator2 =
          new SeriesScanOperator(
              driverContext.getOperatorContexts().get(1),
              planNodeId2,
              measurementPath2,
              Ordering.ASC,
              SeriesScanOptions.getDefaultSeriesScanOptions(measurementPath2));
      seriesScanOperator2.initQueryDataSource(new QueryDataSource(seqResources, unSeqResources));
      seriesScanOperator2
          .getOperatorContext()
          .setMaxRunTime(new Duration(500, TimeUnit.MILLISECONDS));

      FullOuterTimeJoinOperator timeJoinOperator =
          new FullOuterTimeJoinOperator(
              driverContext.getOperatorContexts().get(2),
              Arrays.asList(seriesScanOperator1, seriesScanOperator2),
              Ordering.ASC,
              Arrays.asList(TSDataType.INT32, TSDataType.INT32),
              Arrays.asList(
                  new SingleColumnMerger(new InputLocation(0, 0), new AscTimeComparator()),
                  new SingleColumnMerger(new InputLocation(1, 0), new AscTimeComparator())),
              new AscTimeComparator());
      timeJoinOperator.getOperatorContext().setMaxRunTime(new Duration(500, TimeUnit.MILLISECONDS));

      SingleDeviceViewOperator singleDeviceViewOperator =
          new SingleDeviceViewOperator(
              driverContext.getOperatorContexts().get(3),
              SINGLE_DEVICE_MERGE_OPERATOR_TEST_SG + ".device0",
              timeJoinOperator,
              Arrays.asList(1, 2),
              Arrays.asList(TSDataType.TEXT, TSDataType.INT32, TSDataType.INT32, TSDataType.INT32));
      int count = 0;
      int total = 0;
      while (singleDeviceViewOperator.isBlocked().isDone() && singleDeviceViewOperator.hasNext()) {
        TsBlock tsBlock = singleDeviceViewOperator.next();
        assertEquals(4, tsBlock.getValueColumnCount());
        total += tsBlock.getPositionCount();
        for (int i = 0; i < tsBlock.getPositionCount(); i++) {
          long expectedTime = i + 20L * (count % 25);
          assertEquals(expectedTime, tsBlock.getTimeByIndex(i));
          assertEquals(
              SINGLE_DEVICE_MERGE_OPERATOR_TEST_SG + ".device0",
              tsBlock.getColumn(0).getBinary(i).toString());
          if (expectedTime < 200) {
            assertEquals(20000 + expectedTime, tsBlock.getColumn(1).getInt(i));
            assertEquals(20000 + expectedTime, tsBlock.getColumn(2).getInt(i));
            assertTrue(tsBlock.getColumn(3).isNull(i));
          } else if (expectedTime < 260
              || (expectedTime >= 300 && expectedTime < 380)
              || expectedTime >= 400) {
            assertEquals(10000 + expectedTime, tsBlock.getColumn(1).getInt(i));
            assertEquals(10000 + expectedTime, tsBlock.getColumn(2).getInt(i));
            assertTrue(tsBlock.getColumn(3).isNull(i));
          } else {
            assertEquals(expectedTime, tsBlock.getColumn(1).getInt(i));
            assertEquals(expectedTime, tsBlock.getColumn(2).getInt(i));
            assertTrue(tsBlock.getColumn(3).isNull(i));
          }
        }
        count++;
      }
      assertEquals(500, total);
    } catch (Exception e) {
      e.printStackTrace();
      fail();
    }
  }
Construct seriesScanOperator:[device0.sensor0, device1.sensor1], the result tsBlock should be
like [Device, sensor0, sensor1]. The sensor1 column of device0 and the sensor0 column of
device1 should be null.
iotdb-core/datanode/src/test/java/org/apache/iotdb/db/queryengine/execution/operator/SingleDeviceViewOperatorTest.java