Start work on pooled connections

moor/lib/connection_pool.dart

@@ -0,0 +1,26 @@
+/// Support library to support pooled connections with moor.
+///
+/// Note that using a pooled connection is not necessary for most moor apps.
+@experimental
+library connection_pool;
+
+import 'package:meta/meta.dart';
+import 'package:moor/backends.dart';
+import 'package:moor/moor.dart';
+
+part 'src/runtime/executor/connection_pool_impl.dart';
+
+/// A query executor for moor that delegates work to multiple executors.
+abstract class MultiExecutor extends QueryExecutor {
+  /// Creates a query executor that will delegate work to different executors.
+  ///
+  /// Updating statements, or statements that run in a transaction, will be run
+  /// with [write]. Select statements outside of a transaction are executed on
+  /// [read].
+  factory MultiExecutor(
+      {@required QueryExecutor read, @required QueryExecutor write}) {
+    return _MultiExecutorImpl(read, write);
+  }
+
+  MultiExecutor._();
+}

moor/lib/src/runtime/executor/connection_pool_impl.dart

@@ -0,0 +1,96 @@
+part of 'package:moor/connection_pool.dart';
+
+class _MultiExecutorImpl extends MultiExecutor {
+  final QueryExecutor _reads;
+  final QueryExecutor _writes;
+
+  _MultiExecutorImpl(this._reads, this._writes) : super._();
+
+  @override
+  set databaseInfo(GeneratedDatabase database) {
+    super.databaseInfo = database;
+
+    _writes.databaseInfo = database;
+    _reads.databaseInfo = _NoMigrationsWrapper(database);
+  }
+
+  @override
+  Future<bool> ensureOpen() async {
+    // note: It's crucial that we open the writes first. The reading connection
+    // doesn't run migrations, but has to set the user version.
+    await _writes.ensureOpen();
+    await _reads.ensureOpen();
+
+    return true;
+  }
+
+  @override
+  TransactionExecutor beginTransaction() {
+    return _writes.beginTransaction();
+  }
+
+  @override
+  Future<void> runBatched(List<BatchedStatement> statements) async {
+    await _writes.runBatched(statements);
+  }
+
+  @override
+  Future<void> runCustom(String statement, [List args]) async {
+    await _writes.runCustom(statement, args);
+  }
+
+  @override
+  Future<int> runDelete(String statement, List args) async {
+    return await _writes.runDelete(statement, args);
+  }
+
+  @override
+  Future<int> runInsert(String statement, List args) async {
+    return await _writes.runInsert(statement, args);
+  }
+
+  @override
+  Future<List<Map<String, dynamic>>> runSelect(
+      String statement, List args) async {
+    return await _reads.runSelect(statement, args);
+  }
+
+  @override
+  Future<int> runUpdate(String statement, List args) async {
+    return await _writes.runUpdate(statement, args);
+  }
+
+  @override
+  Future<void> close() async {
+    await _writes.close();
+    await _reads.close();
+  }
+}
+
+// query executors are responsible for starting the migration process on
+// a database after they open. We don't want to run migrations twice, so
+// we give the reading executor a database handle that doesn't do any
+// migrations.
+class _NoMigrationsWrapper extends GeneratedDatabase {
+  final GeneratedDatabase _inner;
+
+  _NoMigrationsWrapper(this._inner)
+      : super(const SqlTypeSystem.withDefaults(), null);
+
+  @override
+  Iterable<TableInfo<Table, DataClass>> get allTables => const [];
+
+  @override
+  int get schemaVersion => _inner.schemaVersion;
+
+  @override
+  Future<void> handleDatabaseCreation({@required SqlExecutor executor}) async {}
+
+  @override
+  Future<void> handleDatabaseVersionChange(
+      {@required SqlExecutor executor, int from, int to}) async {}
+
+  @override
+  Future<void> beforeOpenCallback(
+      QueryExecutor executor, OpeningDetails details) async {}
+}

moor_generator/lib/src/model/declarations/index.dart

@@ -9,8 +9,6 @@ class MoorIndexDeclaration implements MoorDeclaration, IndexDeclaration {
   @override
   final CreateIndexStatement node;
 
-  MoorIndexDeclaration._(this.declaration, this.node);
-
   MoorIndexDeclaration.fromNodeAndFile(this.node, FoundFile file)
       : declaration = SourceRange.fromNodeAndFile(node, file);
 }

moor_generator/lib/src/model/declarations/special_queries.dart

@@ -10,8 +10,6 @@ class MoorSpecialQueryDeclaration
   @override
   final DeclaredStatement node;
 
-  MoorSpecialQueryDeclaration._(this.declaration, this.node);
-
   MoorSpecialQueryDeclaration.fromNodeAndFile(this.node, FoundFile file)
       : declaration = SourceRange.fromNodeAndFile(node, file);
 }

moor_generator/lib/src/model/declarations/trigger.dart

@@ -9,8 +9,6 @@ class MoorTriggerDeclaration implements MoorDeclaration, TriggerDeclaration {
   @override
   final CreateTriggerStatement node;
 
-  MoorTriggerDeclaration._(this.declaration, this.node);
-
   MoorTriggerDeclaration.fromNodeAndFile(this.node, FoundFile file)
       : declaration = SourceRange.fromNodeAndFile(node, file);
 }