Remove database-wide mutex.

Author: rkistner

lib/src/connection_pool.dart

@@ -24,8 +24,6 @@ class SqliteConnectionPool with SqliteQueries implements SqliteConnection {
 
   final String? debugName;
 
-  final Mutex mutex;
-
   @override
   bool closed = false;
 
@@ -44,7 +42,6 @@ class SqliteConnectionPool with SqliteQueries implements SqliteConnection {
       this.maxReaders = 5,
       SqliteConnection? writeConnection,
       this.debugName,
-      required this.mutex,
       required SerializedPortClient upstreamPort})
       : _writeConnection = writeConnection,
         _upstreamPort = upstreamPort;
@@ -128,7 +125,6 @@ class SqliteConnectionPool with SqliteQueries implements SqliteConnection {
         primary: false,
         updates: updates,
         debugName: debugName != null ? '$debugName-writer' : null,
-        mutex: mutex,
         readOnly: false,
         openFactory: _factory);
     return _runZoned(() {
@@ -166,7 +162,6 @@ class SqliteConnectionPool with SqliteQueries implements SqliteConnection {
           primary: false,
           updates: updates,
           debugName: name,
-          mutex: mutex,
           readOnly: true,
           openFactory: _factory);
       _readConnections.add(connection);

lib/src/isolate_connection_factory.dart

@@ -4,7 +4,6 @@ import 'dart:isolate';
 import 'package:sqlite3/sqlite3.dart' as sqlite;
 
 import 'database_utils.dart';
-import 'mutex.dart';
 import 'port_channel.dart';
 import 'sqlite_connection.dart';
 import 'sqlite_connection_impl.dart';
@@ -14,31 +13,24 @@ import 'update_notification.dart';
 /// A connection factory that can be passed to different isolates.
 class IsolateConnectionFactory {
   SqliteOpenFactory openFactory;
-  SerializedMutex mutex;
   SerializedPortClient upstreamPort;
 
   IsolateConnectionFactory(
-      {required this.openFactory,
-      required this.mutex,
-      required this.upstreamPort});
+      {required this.openFactory, required this.upstreamPort});
 
   /// Open a new SqliteConnection.
   ///
   /// This opens a single connection in a background execution isolate.
   SqliteConnection open({String? debugName, bool readOnly = false}) {
     final updates = _IsolateUpdateListener(upstreamPort);
 
-    var openMutex = mutex.open();
-
     return _IsolateSqliteConnection(
         openFactory: openFactory,
-        mutex: openMutex,
         upstreamPort: upstreamPort,
         readOnly: readOnly,
         debugName: debugName,
         updates: updates.stream,
         closeFunction: () async {
-          await openMutex.close();
           updates.close();
         });
   }
@@ -93,7 +85,6 @@ class _IsolateSqliteConnection extends SqliteConnectionImpl {
 
   _IsolateSqliteConnection(
       {required super.openFactory,
-      required super.mutex,
       required super.upstreamPort,
       super.updates,
       super.debugName,

lib/src/sqlite_connection_impl.dart

@@ -18,7 +18,6 @@ typedef TxCallback<T> = Future<T> Function(sqlite.Database db);
 class SqliteConnectionImpl with SqliteQueries implements SqliteConnection {
   /// Private to this connection
   final SimpleMutex _connectionMutex = SimpleMutex();
-  final Mutex _writeMutex;
 
   /// Must be a broadcast stream
   @override
@@ -30,13 +29,11 @@ class SqliteConnectionImpl with SqliteQueries implements SqliteConnection {
 
   SqliteConnectionImpl(
       {required SqliteOpenFactory openFactory,
-      required Mutex mutex,
       required SerializedPortClient upstreamPort,
       this.updates,
       this.debugName,
       this.readOnly = false,
-      bool primary = false})
-      : _writeMutex = mutex {
+      bool primary = false}) {
     _open(openFactory, primary: primary, upstreamPort: upstreamPort);
   }
 
@@ -88,15 +85,7 @@ class SqliteConnectionImpl with SqliteQueries implements SqliteConnection {
   @override
   Future<void> close() async {
     await _connectionMutex.lock(() async {
-      if (readOnly) {
-        await _isolateClient.post(const _SqliteIsolateConnectionClose());
-      } else {
-        // In some cases, disposing a write connection lock the database.
-        // We use the lock here to avoid "database is locked" errors.
-        await _writeMutex.lock(() async {
-          await _isolateClient.post(const _SqliteIsolateConnectionClose());
-        });
-      }
+      await _isolateClient.post(const _SqliteIsolateConnectionClose());
       _isolate.kill();
     });
   }

lib/src/sqlite_database.dart

@@ -4,7 +4,6 @@ import 'dart:isolate';
 import 'connection_pool.dart';
 import 'database_utils.dart';
 import 'isolate_connection_factory.dart';
-import 'mutex.dart';
 import 'port_channel.dart';
 import 'sqlite_connection.dart';
 import 'sqlite_connection_impl.dart';
@@ -24,9 +23,6 @@ class SqliteDatabase with SqliteQueries implements SqliteConnection {
   /// Maximum number of concurrent read transactions.
   final int maxReaders;
 
-  /// Global lock to serialize write transactions.
-  final SimpleMutex mutex = SimpleMutex();
-
   /// Factory that opens a raw database connection in each isolate.
   ///
   /// This must be safe to pass to different isolates.
@@ -87,8 +83,7 @@ class SqliteDatabase with SqliteQueries implements SqliteConnection {
         updates: updates,
         writeConnection: _internalConnection,
         debugName: 'sqlite',
-        maxReaders: maxReaders,
-        mutex: mutex);
+        maxReaders: maxReaders);
 
     _initialized = _init();
   }
@@ -128,7 +123,8 @@ class SqliteDatabase with SqliteQueries implements SqliteConnection {
           // Use the mutex to only send updates after the current transaction.
           // Do take care to avoid getting a lock for each individual update -
           // that could add massive performance overhead.
-          mutex.lock(() async {
+          // FIXME: This lock is not shared across isolates anymore.
+          _pool.writeLock((ctx) async {
             if (updates != null) {
               _updatesController.add(updates!);
               updates = null;
@@ -165,9 +161,7 @@ class SqliteDatabase with SqliteQueries implements SqliteConnection {
   /// Use this to access the database in background isolates.
   IsolateConnectionFactory isolateConnectionFactory() {
     return IsolateConnectionFactory(
-        openFactory: openFactory,
-        mutex: mutex.shared,
-        upstreamPort: _eventsPort.client());
+        openFactory: openFactory, upstreamPort: _eventsPort.client());
   }
 
   SqliteConnectionImpl _openPrimaryConnection({String? debugName}) {
@@ -176,7 +170,6 @@ class SqliteDatabase with SqliteQueries implements SqliteConnection {
         primary: true,
         updates: updates,
         debugName: debugName,
-        mutex: mutex,
         readOnly: false,
         openFactory: openFactory);
   }
@@ -186,7 +179,6 @@ class SqliteDatabase with SqliteQueries implements SqliteConnection {
     await _pool.close();
     _updatesController.close();
     _eventsPort.close();
-    await mutex.close();
   }
 
   /// Open a read-only transaction.