🐛 [firebase_database] get() returns incorrect results on iOS compared to Android or Web

[SoftWyer]

Bug report

When querying the database with a reference that contains four children, the data returned under iOS returns a snapshot from the first three children, not the fourth (e.g. from the reference's parent). The same code works correctly on Android and the Web.

Replacing get() for once() returns the correct data without any changes to the database reference.

Steps to reproduce

The following code works correctly on Android and Web platforms:

  final DatabaseReference ref = FirebaseDatabase.instance.ref();
  
  // Get a reference, e.g. "items/-KbRRDWfIKVKPonCNV3-/-Lv4f4B-Of6qtbMB_21M/-LO9Rmgg6qadElqZW_U2"
  final getRef = ref.child('items').child(i.collectionUid!).child(i.parentUid!).child(i.uid);
 
  // Retrieve the data using get()
  final DataSnapshot snapshot = await getRef.get();

  // snapshot.value contains correct data on Android and Web, but is incorrect on iOS

On iOS, snapshot.value contains the data from the last but one child.

If the above code is changed to use once() in place of get(), then it works on all platforms, e.g.

  final DatabaseReference ref = FirebaseDatabase.instance.ref();
  
  // Get a reference, e.g. "items/-KbRRDWfIKVKPonCNV3-/-Lv4f4B-Of6qtbMB_21M/-LO9Rmgg6qadElqZW_U2"
  final getRef = ref.child('items').child(i.collectionUid!).child(i.parentUid!).child(i.uid);
 
  // Retrieve the data using once()
  final DataSnapshot snapshot = (await getRef.once()).snapshot;

  // snapshot.value contains correct data on all platforms

Futhermore, on iOS, putting additional children (with non-existent data paths) onto the reference still returns data from the third child when using get() whereas it should fail to find any data.

Expected behavior

The get() call should return the same snapshot of data regardless of platform.

---

Flutter doctor

Flutter doctor

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.0.4, on macOS 12.4 21F79 darwin-x64, locale en-GB)
[✗] Android toolchain - develop for Android devices
    ✗ Unable to locate Android SDK.
      Install Android Studio from: https://developer.android.com/studio/index.html
      On first launch it will assist you in installing the Android SDK components.
      (or visit https://flutter.dev/docs/get-started/install/macos#android-setup for detailed instructions).
      If the Android SDK has been installed to a custom location, please use
      `flutter config --android-sdk` to update to that location.

[✓] Xcode - develop for iOS and macOS (Xcode 13.4.1)
[✓] Chrome - develop for the web
[!] Android Studio (not installed)
[✓] VS Code (version 1.69.0)
[✓] VS Code (version 1.51.1)
[✓] Connected device (4 available)
[✓] HTTP Host Availability

! Doctor found issues in 2 categories.

---

Flutter dependencies

Flutter dependencies

Dart SDK 2.17.5
Flutter SDK 3.0.4
collections 2.4.2+200

dependencies:
- archive 3.3.0 [crypto path]
- async 2.8.2 [collection meta]
- badges 2.0.3 [flutter]
- cached_network_image 3.2.1 [flutter flutter_cache_manager octo_image cached_network_image_platform_interface cached_network_image_web]
- charcode 1.3.1
- cloud_firestore 3.2.1 [cloud_firestore_platform_interface cloud_firestore_web collection firebase_core firebase_core_platform_interface flutter meta]
- collection 1.16.0
- connectivity 3.0.6 [flutter meta connectivity_platform_interface connectivity_macos connectivity_for_web]
- csv 5.0.1
- dynamic_theme 2.0.0 [flutter shared_preferences]
- email_validator 2.0.1
- file_picker 4.6.1 [flutter flutter_web_plugins flutter_plugin_android_lifecycle plugin_platform_interface ffi path win32]
- firebase_auth 3.4.1 [firebase_auth_platform_interface firebase_auth_web firebase_core firebase_core_platform_interface flutter meta]
- firebase_core 1.19.1 [firebase_core_platform_interface firebase_core_web flutter meta]
- firebase_crashlytics 2.8.4 [firebase_core firebase_core_platform_interface firebase_crashlytics_platform_interface flutter stack_trace]
- firebase_database 9.0.18 [firebase_core firebase_core_platform_interface firebase_database_platform_interface firebase_database_web flutter]
- firebase_storage 10.3.1 [firebase_core firebase_core_platform_interface firebase_storage_platform_interface firebase_storage_web flutter]
- firebase_ui 1.0.10 [flutter_localizations crypto device_info firebase_auth google_sign_in http sn_progress_dialog sign_in_with_apple]
- flutter 0.0.0 [characters collection material_color_utilities meta vector_math sky_engine]
- flutter_colorpicker 1.0.3 [flutter]
- flutter_html 2.2.1 [html csslib flutter_layout_grid video_player chewie webview_flutter chewie_audio flutter_svg flutter_math_fork collection numerus flutter]
- flutter_localizations 0.0.0 [flutter intl characters clock collection material_color_utilities meta path vector_math]
- flutter_markdown 0.6.10+2 [flutter markdown meta path]
- flutter_speed_dial 6.0.0 [flutter]
- flutter_svg 1.1.1+1 [flutter meta path_drawing vector_math xml]
- google_mobile_ads 1.3.0 [meta flutter]
- hive 2.2.3 [meta crypto]
- hive_flutter 1.1.0 [flutter hive path_provider path]
- html 0.15.0 [csslib source_span]
- i18n_extension 5.0.0 [sprintf args analyzer gettext_parser equatable intl flutter]
- image 3.2.0 [archive meta xml]
- image_cropper 2.0.3 [flutter image_cropper_platform_interface image_cropper_for_web]
- image_picker 0.8.5+3 [flutter image_picker_android image_picker_for_web image_picker_ios image_picker_platform_interface]
- in_app_purchase 3.0.6 [flutter in_app_purchase_android in_app_purchase_platform_interface in_app_purchase_storekit]
- in_app_purchase_android 0.2.3 [collection flutter in_app_purchase_platform_interface json_annotation]
- intl 0.17.0 [clock path]
- json_annotation 4.6.0 [meta]
- markdown 5.0.0 [args charcode meta]
- package_info_plus 1.4.2 [flutter package_info_plus_platform_interface package_info_plus_linux package_info_plus_macos package_info_plus_windows package_info_plus_web]
- path 1.8.1
- path_provider 2.0.11 [flutter path_provider_android path_provider_ios path_provider_linux path_provider_macos path_provider_platform_interface path_provider_windows]
- pdf 3.8.1 [archive barcode crypto image meta path_parsing vector_math xml]
- permission_handler 10.0.0 [flutter meta permission_handler_android permission_handler_apple permission_handler_windows permission_handler_platform_interface]
- photo_view 0.14.0 [flutter]
- printing 5.9.1 [ffi flutter flutter_web_plugins http image js meta pdf plugin_platform_interface]
- provider 6.0.3 [collection flutter nested]
- providerscope 1.0.2 [flutter flutter_image]
- qr_mobile_vision 3.0.1 [flutter native_device_orientation]
- rxdart 0.27.4
- scrollable_positioned_list 0.3.2 [flutter collection]
- share 2.0.4 [meta mime flutter]
- shared_preferences 2.0.15 [flutter shared_preferences_android shared_preferences_ios shared_preferences_linux shared_preferences_macos shared_preferences_platform_interface shared_preferences_web shared_preferences_windows]
- sliver_tools 0.2.7 [flutter]
- sn_progress_dialog 1.0.8 [flutter]
- sprintf 6.0.0
- timeago 3.2.2
- url_launcher 6.1.4 [flutter url_launcher_android url_launcher_ios url_launcher_linux url_launcher_macos url_launcher_platform_interface url_launcher_web url_launcher_windows]

dev dependencies:
- build_runner 2.1.11 [args async analyzer build build_config build_daemon build_resolvers build_runner_core code_builder collection crypto dart_style frontend_server_client glob graphs http_multi_server io js logging meta mime package_config path pool pub_semver pubspec_parse shelf shelf_web_socket stack_trace stream_transform timing watcher web_socket_channel yaml]
- flutter_test 0.0.0 [flutter test_api path fake_async clock stack_trace vector_math async boolean_selector characters charcode collection matcher material_color_utilities meta source_span stream_channel string_scanner term_glyph]
- hive_generator 1.1.3 [build source_gen hive analyzer source_helper]
- json_serializable 6.3.1 [analyzer async build build_config collection json_annotation meta path pub_semver pubspec_parse source_gen source_helper]
- lint 1.8.2

dependency overrides:
- flutter_svg 1.1.1+1 [flutter meta path_drawing vector_math xml]

transitive dependencies:
- _fe_analyzer_shared 38.0.0 [meta]
- analyzer 3.4.1 [_fe_analyzer_shared collection convert crypto glob meta package_config path pub_semver source_span watcher yaml]
- args 2.3.1
- barcode 2.2.1 [meta qr]
- boolean_selector 2.1.0 [source_span string_scanner]
- build 2.3.0 [analyzer async convert crypto glob logging meta path]
- build_config 1.0.0 [checked_yaml json_annotation path pubspec_parse yaml]
- build_daemon 3.1.0 [built_collection built_value http_multi_server logging path pool shelf shelf_web_socket stream_transform watcher web_socket_channel]
- build_resolvers 2.0.9 [analyzer async build crypto graphs logging path package_config pool pub_semver stream_transform yaml]
- build_runner_core 7.2.3 [async build build_config build_resolvers collection convert crypto glob graphs json_annotation logging meta path package_config pool timing watcher yaml]
- built_collection 5.1.1
- built_value 8.3.3 [built_collection collection fixnum meta]
- cached_network_image_platform_interface 1.0.0 [flutter flutter_cache_manager]
- cached_network_image_web 1.0.1 [flutter flutter_cache_manager cached_network_image_platform_interface]
- characters 1.2.0
- checked_yaml 2.0.1 [json_annotation source_span yaml]
- chewie 1.3.4 [cupertino_icons flutter provider video_player wakelock]
- chewie_audio 1.3.0 [cupertino_icons flutter video_player]
- clock 1.1.0
- cloud_firestore_platform_interface 5.5.10 [collection firebase_core flutter meta plugin_platform_interface]
- cloud_firestore_web 2.6.19 [cloud_firestore_platform_interface collection firebase_core firebase_core_web flutter flutter_web_plugins js]
- code_builder 4.1.0 [built_collection built_value collection matcher meta]
- connectivity_for_web 0.4.0+1 [connectivity_platform_interface flutter_web_plugins flutter]
- connectivity_macos 0.2.1+2 [flutter connectivity_platform_interface]
- connectivity_platform_interface 2.0.1 [flutter meta plugin_platform_interface]
- convert 3.0.2 [typed_data]
- cross_file 0.3.3+1 [js meta]
- crypto 3.0.2 [typed_data]
- csslib 0.17.2 [source_span]
- cupertino_icons 1.0.5
- dart_style 2.2.3 [analyzer args path pub_semver source_span]
- device_info 2.0.3 [flutter device_info_platform_interface]
- device_info_platform_interface 2.0.1 [flutter meta plugin_platform_interface]
- equatable 2.0.3 [collection meta]
- fake_async 1.3.0 [clock collection]
- ffi 1.2.1
- file 6.1.2 [meta path]
- firebase_auth_platform_interface 6.3.1 [firebase_core flutter meta plugin_platform_interface]
- firebase_auth_web 3.3.19 [firebase_auth_platform_interface firebase_core firebase_core_web flutter flutter_web_plugins http_parser intl js meta]
- firebase_core_platform_interface 4.4.3 [collection flutter flutter_test meta plugin_platform_interface]
- firebase_core_web 1.6.6 [firebase_core_platform_interface flutter flutter_web_plugins js meta]
- firebase_crashlytics_platform_interface 3.2.10 [collection firebase_core flutter meta plugin_platform_interface]
- firebase_database_platform_interface 0.2.1+10 [collection firebase_core flutter meta plugin_platform_interface]
- firebase_database_web 0.2.0+17 [firebase_core firebase_core_web firebase_database_platform_interface flutter flutter_web_plugins js]
- firebase_storage_platform_interface 4.1.10 [collection firebase_core flutter meta plugin_platform_interface]
- firebase_storage_web 3.2.19 [async firebase_core firebase_core_web firebase_storage_platform_interface flutter flutter_web_plugins http js meta]
- fixnum 1.0.1
- flutter_blurhash 0.7.0 [flutter]
- flutter_cache_manager 3.3.0 [clock collection file flutter http path path_provider pedantic rxdart sqflite uuid]
- flutter_image 1.0.0 [flutter]
- flutter_layout_grid 1.0.6 [flutter collection meta quiver]
- flutter_math_fork 0.6.3+1 [flutter flutter_svg provider meta collection tuple]
- flutter_plugin_android_lifecycle 2.0.6 [flutter]
- flutter_web_plugins 0.0.0 [flutter js characters collection material_color_utilities meta vector_math]
- frontend_server_client 2.1.3 [async path]
- gettext_parser 0.2.0
- glob 2.1.0 [async collection file path string_scanner]
- google_sign_in 5.4.0 [flutter google_sign_in_android google_sign_in_ios google_sign_in_platform_interface google_sign_in_web]
- google_sign_in_android 6.0.1 [flutter google_sign_in_platform_interface]
- google_sign_in_ios 5.4.0 [flutter google_sign_in_platform_interface]
- google_sign_in_platform_interface 2.2.0 [flutter quiver]
- google_sign_in_web 0.10.2 [flutter flutter_web_plugins google_sign_in_platform_interface js]
- graphs 2.1.0 [collection]
- http 0.13.4 [async http_parser meta path]
- http_multi_server 3.2.1 [async]
- http_parser 4.0.1 [collection source_span string_scanner typed_data]
- image_cropper_for_web 0.0.4 [flutter flutter_web_plugins image_cropper_platform_interface js]
- image_cropper_platform_interface 2.0.0 [flutter plugin_platform_interface http]
- image_picker_android 0.8.5+1 [flutter flutter_plugin_android_lifecycle image_picker_platform_interface]
- image_picker_for_web 2.1.8 [flutter flutter_web_plugins image_picker_platform_interface]
- image_picker_ios 0.8.5+6 [flutter image_picker_platform_interface]
- image_picker_platform_interface 2.5.0 [cross_file flutter http plugin_platform_interface]
- in_app_purchase_platform_interface 1.3.1 [flutter plugin_platform_interface]
- in_app_purchase_storekit 0.3.1 [collection flutter in_app_purchase_platform_interface json_annotation]
- io 1.0.3 [meta path string_scanner]
- js 0.6.4
- logging 1.0.2
- matcher 0.12.11 [stack_trace]
- material_color_utilities 0.1.4
- meta 1.7.0
- mime 1.0.2
- native_device_orientation 1.1.4 [flutter meta]
- nested 1.0.0 [flutter]
- numerus 1.1.1
- octo_image 1.0.2 [flutter flutter_blurhash]
- package_config 2.1.0 [path]
- package_info_plus_linux 1.0.5 [package_info_plus_platform_interface flutter path]
- package_info_plus_macos 1.3.0 [flutter]
- package_info_plus_platform_interface 1.0.2 [flutter meta plugin_platform_interface]
- package_info_plus_web 1.0.5 [flutter flutter_web_plugins http meta package_info_plus_platform_interface]
- package_info_plus_windows 1.0.5 [package_info_plus_platform_interface ffi flutter win32]
- path_drawing 1.0.0 [vector_math meta path_parsing flutter]
- path_parsing 1.0.0 [vector_math meta]
- path_provider_android 2.0.16 [flutter path_provider_platform_interface]
- path_provider_ios 2.0.10 [flutter path_provider_platform_interface]
- path_provider_linux 2.1.7 [ffi flutter path path_provider_platform_interface xdg_directories]
- path_provider_macos 2.0.6 [flutter path_provider_platform_interface]
- path_provider_platform_interface 2.0.4 [flutter platform plugin_platform_interface]
- path_provider_windows 2.0.7 [ffi flutter path path_provider_platform_interface win32]
- pedantic 1.11.1
- permission_handler_android 10.0.0 [flutter permission_handler_platform_interface]
- permission_handler_apple 9.0.4 [flutter permission_handler_platform_interface]
- permission_handler_platform_interface 3.7.0 [flutter meta plugin_platform_interface]
- permission_handler_windows 0.1.0 [flutter permission_handler_platform_interface]
- petitparser 5.0.0 [meta]
- platform 3.1.0
- plugin_platform_interface 2.1.2 [meta]
- pool 1.5.1 [async stack_trace]
- process 4.2.4 [file path platform]
- pub_semver 2.1.1 [collection meta]
- pubspec_parse 1.2.0 [checked_yaml collection json_annotation pub_semver yaml]
- qr 3.0.1 [meta]
- quiver 3.1.0 [matcher]
- shared_preferences_android 2.0.12 [flutter shared_preferences_platform_interface]
- shared_preferences_ios 2.1.1 [flutter shared_preferences_platform_interface]
- shared_preferences_linux 2.1.1 [file flutter path path_provider_linux path_provider_platform_interface shared_preferences_platform_interface]
- shared_preferences_macos 2.0.4 [flutter shared_preferences_platform_interface]
- shared_preferences_platform_interface 2.0.0 [flutter]
- shared_preferences_web 2.0.4 [flutter flutter_web_plugins shared_preferences_platform_interface]
- shared_preferences_windows 2.1.1 [file flutter path path_provider_platform_interface path_provider_windows shared_preferences_platform_interface]
- shelf 1.3.1 [async collection http_parser path stack_trace stream_channel]
- shelf_web_socket 1.0.2 [shelf stream_channel web_socket_channel]
- sign_in_with_apple 3.3.0 [flutter meta sign_in_with_apple_platform_interface sign_in_with_apple_web]
- sign_in_with_apple_platform_interface 1.0.0 [flutter plugin_platform_interface meta]
- sign_in_with_apple_web 1.0.1 [flutter flutter_web_plugins sign_in_with_apple_platform_interface js]
- sky_engine 0.0.99
- source_gen 1.2.2 [analyzer async build dart_style glob meta path source_span yaml]
- source_helper 1.3.2 [analyzer collection source_gen]
- source_span 1.8.2 [collection path term_glyph]
- sqflite 2.0.3 [flutter sqflite_common path]
- sqflite_common 2.2.1+1 [synchronized path meta]
- stack_trace 1.10.0 [path]
- stream_channel 2.1.0 [async]
- stream_transform 2.0.0
- string_scanner 1.1.0 [charcode source_span]
- synchronized 3.0.0+2
- term_glyph 1.2.0
- test_api 0.4.9 [async boolean_selector collection meta source_span stack_trace stream_channel string_scanner term_glyph matcher]
- timing 1.0.0 [json_annotation]
- tuple 2.0.0 [quiver]
- typed_data 1.3.1 [collection]
- url_launcher_android 6.0.17 [flutter url_launcher_platform_interface]
- url_launcher_ios 6.0.17 [flutter url_launcher_platform_interface]
- url_launcher_linux 3.0.1 [flutter url_launcher_platform_interface]
- url_launcher_macos 3.0.1 [flutter url_launcher_platform_interface]
- url_launcher_platform_interface 2.1.0 [flutter plugin_platform_interface]
- url_launcher_web 2.0.12 [flutter flutter_web_plugins url_launcher_platform_interface]
- url_launcher_windows 3.0.1 [flutter url_launcher_platform_interface]
- uuid 3.0.6 [crypto]
- vector_math 2.1.2
- video_player 2.4.5 [flutter html video_player_android video_player_avfoundation video_player_platform_interface video_player_web]
- video_player_android 2.3.6 [flutter video_player_platform_interface]
- video_player_avfoundation 2.3.5 [flutter video_player_platform_interface]
- video_player_platform_interface 5.1.3 [flutter plugin_platform_interface]
- video_player_web 2.0.10 [flutter flutter_web_plugins video_player_platform_interface]
- wakelock 0.6.2 [flutter meta wakelock_macos wakelock_platform_interface wakelock_web wakelock_windows]
- wakelock_macos 0.4.0 [flutter flutter_web_plugins wakelock_platform_interface]
- wakelock_platform_interface 0.3.0 [flutter meta]
- wakelock_web 0.4.0 [flutter flutter_web_plugins js wakelock_platform_interface]
- wakelock_windows 0.2.0 [flutter wakelock_platform_interface win32]
- watcher 1.0.1 [async path]
- web_socket_channel 2.2.0 [async crypto stream_channel]
- webview_flutter 2.8.0 [flutter webview_flutter_android webview_flutter_platform_interface webview_flutter_wkwebview]
- webview_flutter_android 2.8.14 [flutter webview_flutter_platform_interface]
- webview_flutter_platform_interface 1.9.1 [flutter meta plugin_platform_interface]
- webview_flutter_wkwebview 2.8.1 [flutter path webview_flutter_platform_interface]
- win32 2.6.1 [ffi]
- xdg_directories 0.2.0+1 [meta path process]
- xml 6.1.0 [collection meta petitparser]
- yaml 3.1.1 [collection source_span string_scanner]

---

[darshankawar]

@SoftWyer Thanks for the report. Can you provide your database structure, to know how is the parent and children are aligned ? Can you also try the database plugin example and see if using it, you get same behavior as reported ?

[SoftWyer]

I'll see if I can replicate the issue with the example.

The items part of the DB schema captures the items in a user's collection and is structured as:

items leaf -> collections -> containers -> items -> item/container

All the references are coded as UIDs, it looks like this:

[darshankawar]

Thanks for the update. This could very well be an issue with get() api as also mentioned by firebaser here: https://stackoverflow.com/a/71180754. Since, firebase_datbase plugin is a wrapper around native firebase sdks, it leverages the api implementation and receives result through Dart as-is. So I suggest you to open this issue in firebase-ios-sdk github for further resolution. Meantime, you may continue to use once() as it works as expected per your earlier comment and also suggested in the SO link.

Closing from here. If you disagree, write in comments and I'll reopen it.

[g-apparence]

How can this issue be closed? This is a critical bug to follow. We should have a reference to the firebase ios sdk issue here and check this is fixed in next version.

[SoftWyer]

How can this issue be closed? This is a critical bug to follow. We should have a reference to the firebase ios sdk issue here and check this is fixed in next version.

From the comments in the SO issue it sounds like the firebase team is working on an overhaul of how get works which might fix this issue. I don't think there is an explicit issue for this as they had trouble replicating it.

I think the onus is on the users (i.e. us) to raise a bug to track in the correct repository and I was contemplating doing just that, but got sidetracked as there is an official work-around using once.

However, for completeness I raised it here. Please add any relevant comments, especially if you have a repeatable example to that issue :-)

[g-apparence]

Thank you for the answer and for providing the ios issue related so we can follow this.

[paulb777]

@darshankawar Reopening here since the repro is Dart and issues for https://github.com/firebase/firebase-ios-sdk should be Swift or Objective C. See https://github.com/firebase/firebase-ios-sdk/issues/10029#issuecomment-1191269864. Please reach out to me if you'd like to discuss.

[darshankawar]

Thanks @paulb777 for the input. My initial reasoning was based on the comment from SO link I shared earlier.

@SoftWyer currently the demo app and database setup I've is like below:

I'll try to recreate the db structure like the way you shared earlier. Meantime, can you provide complete minimal reproducible code sample (ex: main.dart) that we can directly use ?

[SoftWyer]

@darshankawar I had a look at this again over the weekend. I can successfully reproduce the issue with the app, but trying to break this out into a smaller problem is proving tricky. The problem invariably goes away when reducing the complexity.

I've been trying to get the flutterfire logging working on iOS, but am not sure where to see the logs. They don't appear in the main device logs when viewing using "console". Android logging seems to work fine and spams the log like crazy 😆

[darshankawar]

Thanks for the update. I tried replicating using plugin's example but was unable to see same behavior. I am keeping this issue open and labeling for further insights from the team on know if this is a potential issue or limitation.

/cc @russellwheatley.

[russellwheatley]

Hey @SoftWyer, I'm happy to look into this once there is an MCVE.

[google-oss-bot]

Hey @SoftWyer. We need more information to resolve this issue but there hasn't been an update in 7 weekdays. I'm marking the issue as stale and if there are no new updates in the next 7 days I will close it automatically.

If you have more information that will help us get to the bottom of this, just add a comment!

[google-oss-bot]

Since there haven't been any recent updates here, I am going to close this issue.

@SoftWyer if you're still experiencing this problem and want to continue the discussion just leave a comment here and we are happy to re-open this.