Add helper method to setup isolates more easily

docs/lib/snippets/drift_files/getting_started/database.dart

@@ -27,6 +27,7 @@ LazyDatabase _openConnection() {
     // for your app.
     final dbFolder = await getApplicationDocumentsDirectory();
     final file = File(p.join(dbFolder.path, 'db.sqlite'));
-    return NativeDatabase(file);
+
+    return NativeDatabase.createInBackground(file);
   });
 }

docs/lib/snippets/isolates.dart

@@ -127,3 +127,16 @@ DatabaseConnection createDriftIsolateAndConnect() {
   }));
 }
 // #enddocregion init_connect
+
+// #docregion simple
+QueryExecutor createSimple() {
+  return LazyDatabase(() async {
+    final dir = await getApplicationDocumentsDirectory();
+    final file = File(p.join(dir.path, 'db.sqlite'));
+
+    // Using createInBackground creates a drift isolate with the recommended
+    // options behind the scenes.
+    return NativeDatabase.createInBackground(file);
+  });
+}
+// #enddocregion simple

docs/lib/snippets/tables/filename.dart

@@ -60,7 +60,7 @@ LazyDatabase _openConnection() {
     // for your app.
     final dbFolder = await getApplicationDocumentsDirectory();
     final file = File(p.join(dbFolder.path, 'db.sqlite'));
-    return NativeDatabase(file);
+    return NativeDatabase.createInBackground(file);
   });
 }
 

docs/pages/docs/Advanced Features/isolates.md

@@ -36,6 +36,28 @@ a background isolate. Zero code changes are needed for queries!
 
 {% assign snippets = 'package:drift_docs/snippets/isolates.dart.excerpt.json' | readString | json_decode %}
 
+## Simple setup
+
+Starting from Drift version 2.3.0, using drift isolates has been greatly
+simplified. Simply use `NativeDatabase.createInBackground` as a drop-in
+replacement for the `NativeDatabase` you've been using before:
+
+{% include "blocks/snippet" snippets = snippets name = 'simple' %}
+
+In the common case where you only need a isolate for performance reasons, this
+is as simple as it gets.
+The rest of this article explains a more complex setup giving you full control
+over the internal components making up a drift isolate. This is useful for
+advanced use cases, including:
+
+- Having two databases on different isolates which need to stay in sync.
+- Sharing a drift database connection across different Dart or Flutter engines,
+  like for a background service on Android.
+
+In most other cases, simply using `NativeDatabase.createInbackground` works
+great! It implements the same approach shared in this article, except that all
+the complicated bits are hidden behind a simple method.
+
 ## Preparations
 
 To use the isolate api, first enable the appropriate [build option]({{ "builder_options.md" | pageUrl }}) by

docs/pages/docs/Examples/existing_databases.md

@@ -60,7 +60,7 @@ LazyDatabase _openConnection() {
         await file.writeAsBytes(buffer.asUint8List(blob.offsetInBytes, blob.lengthInBytes));
     }
 
-    return NativeDatabase(file);
+    return NativeDatabase.createInBackground(file);;
   });
 }
 ```

drift/CHANGELOG.md

@@ -9,6 +9,9 @@
 - Add `singleClientMode` to `remote()` and `DriftIsolate` connections to make
   the common case with one client more efficient.
 - Fix a concurrency issues around transactions.
+- Add `NativeDatabase.createInBackground` as a drop-in replacement for
+  `NativeDatabase`. It creates a drift isolate behind the scenes, avoiding all
+  of the boilerplate usually involved with drift isolates.
 - __Experimental__: Add a [modular generation mode](https://drift.simonbinder.eu/docs/advanced-features/builder_options/#enabling-modular-code-generation)
   in which drift will generate multiple smaller files instead of one very large
   one with all tables and generated queries.

drift/lib/native.dart

@@ -10,7 +10,10 @@
 library drift.ffi;
 
 import 'dart:io';
+import 'dart:isolate';
 
+import 'package:drift/drift.dart';
+import 'package:drift/isolate.dart';
 import 'package:meta/meta.dart';
 import 'package:sqlite3/common.dart';
 import 'package:sqlite3/sqlite3.dart';
@@ -50,6 +53,53 @@ class NativeDatabase extends DelegatedDatabase {
     return NativeDatabase._(_NativeDelegate(file, setup), logStatements);
   }
 
+  /// Creates a database storing its result in [file].
+  ///
+  /// This method will create the same database as the default constructor of
+  /// the [NativeDatabase] class. It also behaves the same otherwise: The [file]
+  /// is created if it doesn't exist, [logStatements] can be used to print
+  /// statements and [setup] can be used to perform a one-time setup work when
+  /// the database is created.
+  ///
+  /// The big distinction of this method is that the database is implicitly
+  /// created on a background isolate, freeing up your main thread accessing the
+  /// database from I/O work needed to run statements.
+  /// When the database returned by this method is closed, the background
+  /// isolate will shut down as well.
+  ///
+  /// __Important limitations__: If the [setup] parameter is given, it must be
+  /// a static or top-level function. The reason is that it is executed on
+  /// another isolate.
+  static QueryExecutor createInBackground(File file,
+      {bool logStatements = false, DatabaseSetup? setup}) {
+    return createBackgroundConnection(file,
+            logStatements: logStatements, setup: setup)
+        .executor;
+  }
+
+  /// Like [createInBackground], except that it returns the whole
+  /// [DatabaseConnection] instead of just the executor.
+  ///
+  /// This creates a database writing data to the given [file]. The database
+  /// runs in a background isolate and is stopped when closed.
+  static DatabaseConnection createBackgroundConnection(File file,
+      {bool logStatements = false, DatabaseSetup? setup}) {
+    return DatabaseConnection.delayed(Future.sync(() async {
+      final receiveIsolate = ReceivePort();
+      await Isolate.spawn(
+        _NativeIsolateStartup.start,
+        _NativeIsolateStartup(
+            file.absolute.path, logStatements, setup, receiveIsolate.sendPort),
+        debugName: 'Drift isolate worker for ${file.path}',
+      );
+
+      final driftIsolate = await receiveIsolate.first as DriftIsolate;
+      receiveIsolate.close();
+
+      return driftIsolate.connect(singleClientMode: true);
+    }));
+  }
+
   /// Creates an in-memory database won't persist its changes on disk.
   ///
   /// {@macro drift_vm_database_factory}
@@ -204,3 +254,25 @@ class _NativeDelegate extends Sqlite3Delegate<Database> {
     }
   }
 }
+
+class _NativeIsolateStartup {
+  final String path;
+  final bool enableLogs;
+  final DatabaseSetup? setup;
+  final SendPort sendServer;
+
+  _NativeIsolateStartup(
+      this.path, this.enableLogs, this.setup, this.sendServer);
+
+  static void start(_NativeIsolateStartup startup) {
+    final isolate = DriftIsolate.inCurrent(() {
+      return DatabaseConnection(NativeDatabase(
+        File(startup.path),
+        logStatements: startup.enableLogs,
+        setup: startup.setup,
+      ));
+    });
+
+    startup.sendServer.send(isolate);
+  }
+}

drift/pubspec.yaml

@@ -35,3 +35,4 @@ dev_dependencies:
   rxdart: ^0.27.0
   shelf: ^1.3.0
   stack_trace: ^1.10.0
+  test_descriptor: ^2.0.1

drift/test/platforms/ffi/native_database_test.dart

@@ -1,14 +1,41 @@
 @TestOn('vm')
+import 'dart:io';
+
 import 'package:drift/drift.dart';
 import 'package:drift/native.dart';
 import 'package:sqlite3/sqlite3.dart';
 import 'package:test/test.dart';
+import 'package:test_descriptor/test_descriptor.dart' as d;
 
+import '../../generated/todos.dart';
 import '../../test_utils/database_vm.dart';
 
 void main() {
   preferLocalSqlite3();
 
+  group('implicit isolates', () {
+    test('work with direct executors', () async {
+      final file = File(d.path('test.db'));
+
+      final db = TodoDb(NativeDatabase.createInBackground(file));
+      await db.todosTable.select().get(); // Open the database
+      await db.close();
+
+      await d.file('test.db', anything).validate();
+    });
+
+    test('work with connections', () async {
+      final file = File(d.path('test.db'));
+
+      final db =
+          TodoDb.connect(NativeDatabase.createBackgroundConnection(file));
+      await db.todosTable.select().get(); // Open the database
+      await db.close();
+
+      await d.file('test.db', anything).validate();
+    });
+  });
+
   group('NativeDatabase.opened', () {
     test('disposes the underlying database by default', () async {
       final underlying = sqlite3.openInMemory();

examples/app/lib/database/connection/native.dart

@@ -1,63 +1,21 @@
 import 'dart:io';
-import 'dart:isolate';
 
 import 'package:drift/drift.dart';
-import 'package:drift/isolate.dart';
 import 'package:drift/native.dart';
 import 'package:path_provider/path_provider.dart';
 import 'package:path/path.dart' as p;
 
 /// Obtains a database connection for running drift in a Dart VM.
-///
-/// The [NativeDatabase] from drift will synchronously use sqlite3's C APIs.
-/// To move synchronous database work off the main thread, we use a
-/// [DriftIsolate], which can run queries in a background isolate under the
-/// hood.
 DatabaseConnection connect() {
-  return DatabaseConnection.delayed(Future.sync(() async {
+  return DatabaseConnection.delayed(Future(() async {
     // Background isolates can't use platform channels, so let's use
     // `path_provider` in the main isolate and just send the result containing
     // the path over to the background isolate.
+
+    // We use `path_provider` to find a suitable path to store our data in.
     final appDir = await getApplicationDocumentsDirectory();
     final dbPath = p.join(appDir.path, 'todos.db');
 
-    final receiveDriftIsolate = ReceivePort();
-    await Isolate.spawn(_entrypointForDriftIsolate,
-        _IsolateStartRequest(receiveDriftIsolate.sendPort, dbPath));
-
-    final driftIsolate = await receiveDriftIsolate.first as DriftIsolate;
-
-    // Each connect() spawns a new isolate which is only used for one
-    // connection, so we shutdown the isolate when the database is closed.
-    return driftIsolate.connect(singleClientMode: true);
+    return NativeDatabase.createBackgroundConnection(File(dbPath));
   }));
 }
-
-/// The entrypoint of isolates can only take a single message, but we need two
-/// (a send port to reach the originating isolate and the database's path that
-/// should be opened on the background isolate). So, we bundle this information
-/// in a single class.
-class _IsolateStartRequest {
-  final SendPort talkToMain;
-  final String databasePath;
-
-  _IsolateStartRequest(this.talkToMain, this.databasePath);
-}
-
-/// The entrypoint for a background isolate launching a drift server.
-///
-/// The main isolate can then connect to that isolate server to transparently
-/// run queries in the background.
-void _entrypointForDriftIsolate(_IsolateStartRequest request) {
-  // The native database synchronously uses sqlite3's C API with `dart:ffi` for
-  // a fast database implementation that doesn't require platform channels.
-  final databaseImpl = NativeDatabase(File(request.databasePath));
-
-  // We can use DriftIsolate.inCurrent because this function is the entrypoint
-  // of a background isolate itself.
-  final driftServer =
-      DriftIsolate.inCurrent(() => DatabaseConnection(databaseImpl));
-
-  // Inform the main isolate about the server we just created.
-  request.talkToMain.send(driftServer);
-}