Flutter Application – Upgrading Database with sqflite

Article Catalog

Description of the problem

After the release of the application developed using fluttter, I realized that the database is not well designed. How to update the database? Using sqflite to handle the database, but after the first version of the software was released, I realized that the database didn’t quite make sense to change, and I wanted to update the database after the new application installation was launched. Here is how to change the name of a table called timerdata to taskdata when a new version of the application is launched.

concrete approach

In Flutter, database upgrades are handled using sqflite’s openDatabase method. When you need to change the database structure, theDatabase upgrades can be triggered by increasing the database version number. In the openDatabase method, you can provide aonUpgrade callbackThis callback will be called when the database is upgraded.

code example

Below is a simple example demonstrating how to update the database when a new version of the application is launched:

import 'package:sqflite/sqflite.dart';
import 'package:path/path.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await updateDatabase();
  runApp(MyApp());
}

Future<void> updateDatabase() async {
  // Open the database and specify the database version
  Database database = await openDatabase(
    join(await getDatabasesPath(), 'your_database.db'),
    version: 2, // update the database version number
    onCreate: (db, version) {
      // Actions performed when the database is first created
      db.execute('CREATE TABLE taskdata(id INTEGER PRIMARY KEY, name TEXT)');
    },
    onUpgrade: (db, oldVersion, newVersion) {
      // Actions performed during database upgrades
      if (oldVersion < 2) {
        // If the old version is less than 2, perform an update.
        db.execute('ALTER TABLE timerdata RENAME TO taskdata');
      }
    },
  );

  // Close the database connection
  await database.close();
}

In the above example, we use the onUpgrade callback to detect a change in the database version number. If the old version is less than 2, we executed a SQL statement to rename the timerdata table to taskdata. please note that this is just a simple example, in reality, you may need to perform more complex database migration operations such as data migration and backup.

More Conditional Upgrades

If your previous database version was 1, and now you want to upgrade the version to 2, and change the name of the table during the upgrade process, you can use the onUpgrade callback to perform the appropriate database migration operation, and restrict the update operation to the current database version of 1 and the target version of 2. The following is a simple example:

import 'package:sqflite/sqflite.dart';
import 'package:path/path.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await updateDatabase();
  runApp(MyApp());
}

Future<void> updateDatabase() async {
  // Open the database and specify the database version
  Database database = await openDatabase(
    join(await getDatabasesPath(), 'your_database.db'),
    version: 2, // update the database version number
    onCreate: (db, version) {
      // Actions performed when the database is first created
      db.execute('CREATE TABLE timerdata(id INTEGER PRIMARY KEY, name TEXT)');
    },
    onUpgrade: (db, oldVersion, newVersion) async {
      // Actions performed during database upgrades
      if (oldVersion == 1 && newVersion == 2) {
        // If the current database version is 1 and the target version is 2, perform the update operation
        await db.execute('ALTER TABLE timerdata RENAME TO taskdata');
      }
    },
  );

  // Close the database connection
  await database.close();
}

In the above code, we set the condition in the onUpgrade callback to perform the update operation if the current database version is 1 and the target version is 2. In this example, we use the ALTER TABLE statement to change the name of the table from timerdata to taskdata.

Introduction to Database Migration and Backup

Database migration and backup is a complex task that requires careful consideration of changes to the database structure and how the data will be retained and transferred. The following general steps are provided for your reference:

Database migration

Determine the database version number: Increment the database version number each time the database structure changes in different versions of the application. Perform database operations in onCreate and onUpgrade: Use the onCreate callback to create the initial database structure, and use the onUpgrade callback to perform database upgrade operations. Handling Data Migration in onUpgrade: If the database table structure changes, you may need to write appropriate SQL statements to migrate the data. This may include creating a new table, copying data from the old table to the new table, and then deleting the old table. Using the ALTER TABLE Statement: For simple structural changes, such as table renaming, you can use the ALTER TABLE statement. Consider using third-party libraries: There are third-party libraries, such as moor and floor, that provide a higher level of database abstraction that can simplify the database migration process.

Database Backup

Using Database Backup Tools: Some database management systems (DBMS) provide backup tools that you can use to perform database backups manually or automatically. For example, SQLite provides the .dump command for exporting database contents. Customized Backup Logic: If no automated backup tool is provided, you may need to write customized logic to backup the database. This includes copying the database files to another location or packing them into a zip file. Regular Backups: Set up a regular backup policy to ensure that the database is backed up in a timely manner. This is especially important because user data can change at any time. Cloud Services: Consider using cloud services for backup to ensure data security. Cloud services such as Firebase, AWS S3, etc. provide powerful backup and storage capabilities. Sample code may vary from case to case, but here is a simplified example of database migration and backup in Flutter using the sqflite library:

import 'package:sqflite/sqflite.dart';
import 'package:path/path.dart';

Future<void> migrateDatabase(Database db, int oldVersion, int newVersion) async {
  if (oldVersion < 2) {
    // Database version is less than 2, perform migration
    await db.execute('ALTER TABLE timerdata RENAME TO taskdata');
  }
  // Migration logic for other versions can be added here
}

Future<void> backupDatabase(String sourcePath, String destinationPath) async {
  // Backup database, which can be a simple file copy
  // or use a compression algorithm to package the file into a zip file
  // Choose the appropriate backup method for your needs
  // For example, using the File and Directory classes from the dart:io library
  // or use third-party libraries such as path_provider and archive
}

void main() async {
  WidgetsFlutterBinding.ensureInitialized();

  // Open the database and specify the database version
  Database database = await openDatabase(
    join(await getDatabasesPath(), 'your_database.db'),
    version: 2, // update the database version number
    onCreate: (db, version) {
      // Actions performed when the database is first created
      db.execute('CREATE TABLE timerdata(id INTEGER PRIMARY KEY, name TEXT)');
    },
    onUpgrade: migrateDatabase,
  );

  // Close the database connection
  await database.close();

  // Backup database
  await backupDatabase(
    join(await getDatabasesPath(), 'your_database.db'),
    '/path/to/backup/your_database_backup.db',
  );

  runApp(MyApp());
}

In practice, you may need to write more complex migration and backup logic based on specific requirements and database structure.

---

concluding remarksFlutter is an open source UI toolkit developed by Google that allows you to create high-quality, aesthetically pleasing applications on different platforms without having to write tons of platform-specific code. I will be learning and delving into all aspects of Flutter. From basics to advanced techniques, from UI design to performance optimization, enjoy following along to discuss and learn together and enter the exciting world of Flutter!