UPDATE a BLOB field in an existing SQLite record，floor change it to String

[HXiaoMing]

the entity is:
@entity(tableName: 'Task')
class Task {
final Uint8List ext;
Task(this.ext);
}

the dao is :
@dao
abstract class TaskDao {
@query('update Task set ext = :ext')
Future updateTaskExt(Uint8List ext);
}

i want to update column ext, ext type is Uint8List，database type is blob，after execute TaskDao method updateTaskExt，ext value change to String！！！

[dkaera]

Please double it check. For me, following configuration works fine:

@Database(version: 1, entities: [Task])
abstract class FlutterDatabase extends FloorDatabase {
  TaskDao get taskDao;
}

@dao
abstract class TaskDao {

  @Query('UPDATE Task set ext = :ext')
  Future<void> updateTaskExt(Uint8List ext);
}

@entity
class Task {
  @PrimaryKey(autoGenerate: true)
  final int? id;

  final String message;

  final Uint8List ext;

  Task(this.id, this.message, this.ext);

}

generates next code:

class _$TaskDao extends TaskDao {
  _$TaskDao(this.database, this.changeListener)
      : _queryAdapter = QueryAdapter(database);

  final sqflite.DatabaseExecutor database;

  final StreamController<String> changeListener;

  final QueryAdapter _queryAdapter;

  @override
  Future<void> updateTaskExt(Uint8List ext) async {
    await _queryAdapter
        .queryNoReturn('UPDATE Task set ext = ?1', arguments: [ext]);
  }
}

[dkaera]

Close due to lack of answer from the creator of the question. Looks like the question might be solved by the suggestion in the comment.

[HXiaoMing]

Please double it check. For me, following configuration works fine:

@Database(version: 1, entities: [Task])
abstract class FlutterDatabase extends FloorDatabase {
  TaskDao get taskDao;
}

@dao
abstract class TaskDao {

  @Query('UPDATE Task set ext = :ext')
  Future<void> updateTaskExt(Uint8List ext);
}

@entity
class Task {
  @PrimaryKey(autoGenerate: true)
  final int? id;

  final String message;

  final Uint8List ext;

  Task(this.id, this.message, this.ext);

}

generates next code:

class _$TaskDao extends TaskDao {
  _$TaskDao(this.database, this.changeListener)
      : _queryAdapter = QueryAdapter(database);

  final sqflite.DatabaseExecutor database;

  final StreamController<String> changeListener;

  final QueryAdapter _queryAdapter;

  @override
  Future<void> updateTaskExt(Uint8List ext) async {
    await _queryAdapter
        .queryNoReturn('UPDATE Task set ext = ?1', arguments: [ext]);
  }
}

after updateTaskExt，try to read it， then will throw error.

[dkaera]

Hey @HXiaoMing
I did some investigation and sflite has the same problem. Honestly, using query to update the data is not the right way to go, but it is possible in some extreme cases as a workaround. For this particular case I would recommend you use rawUpdate. Sample of the code you can see in my PR to your repository.

PS: this issue brings me an idea that DatabaseExecutor should be accessible in DAO classes to use raw methods without global variables. Thanks 👍

[SEGVeenstra]

Closing: Inactive