Fix order

CHANGELOG.md

@@ -46,6 +46,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added information to export CVAT_HOST when performing local installation for accessing over network (<https://github.com/openvinotoolkit/cvat/pull/4014>)
 - Fixed possible color collisions in the generated colormap (<https://github.com/openvinotoolkit/cvat/pull/4007>)
 - Original pdf file is deleted when using share(<https://github.com/openvinotoolkit/cvat/pull/3967>)
+- Order in an annotation file(<https://github.com/openvinotoolkit/cvat/pull/4087>)
 
 ### Security
 - Updated ELK to 6.8.22 which uses log4j 2.17.0 (<https://github.com/openvinotoolkit/cvat/pull/4052>)

cvat/apps/dataset_manager/bindings.py

@@ -1,5 +1,5 @@
 
-# Copyright (C) 2019-2020 Intel Corporation
+# Copyright (C) 2019-2021 Intel Corporation
 #
 # SPDX-License-Identifier: MIT
 

cvat/apps/dataset_manager/task.py

@@ -7,6 +7,7 @@
 from enum import Enum
 
 from django.db import transaction
+from django.db.models.query import Prefetch
 from django.utils import timezone
 
 from cvat.apps.engine import models, serializers
@@ -547,7 +548,9 @@ def import_annotations(self, src_file, importer):
 
 class TaskAnnotation:
     def __init__(self, pk):
-        self.db_task = models.Task.objects.prefetch_related("data__images").get(id=pk)
+        self.db_task = models.Task.objects.prefetch_related(
+            Prefetch('data__images', queryset=models.Image.objects.order_by('frame'))
+        ).get(id=pk)
 
         # Postgres doesn't guarantee an order by default without explicit order_by
         self.db_jobs = models.Job.objects.select_related("segment").filter(segment__task_id=pk).order_by('id')