mirror of https://github.com/AMT-Cheif/drift.git
Transactions for the web backend
This commit is contained in:
Simon Binder
parent
1c423d9d7b
commit
54fb22d970
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@ -11,6 +11,7 @@ import 'dart:indexed_db';
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import 'package:meta/meta.dart';
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import 'package:meta/dart2js.dart';
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import 'package:synchronized/synchronized.dart';
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import 'moor.dart';
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import 'src/web/sql_js.dart';
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@ -1,20 +1,172 @@
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part of 'package:moor/moor_web.dart';
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class _DbState {
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final String name;
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final bool logStatements;
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final Lock lock = Lock();
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SqlJsDatabase db;
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_DbState(this.name, this.logStatements);
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}
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abstract class _DatabaseUser extends QueryExecutor {
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final _DbState _state;
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String get name => _state.name;
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bool get logStatements => _state.logStatements;
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SqlJsDatabase get _db => _state.db;
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bool get _bypassLock => false;
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String get _persistenceKey => 'moor_db_str_$name';
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_DatabaseUser(this._state);
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Future<T> _synchronized<T>(FutureOr<T> computation()) async {
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final lock = _state.lock;
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if (_bypassLock) {
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return await computation();
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}
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return await lock.synchronized(computation);
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}
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// todo base64 works, but is very slow. Figure out why bin2str is broken
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Uint8List _restoreDb() {
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final raw = window.localStorage[_persistenceKey];
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if (raw != null) {
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return base64.decode(raw);
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}
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return null;
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}
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void _storeDb() {
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final data = _db.export();
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final binStr = base64.encode(data);
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window.localStorage[_persistenceKey] = binStr;
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}
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@tryInline
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void _log(String sql, List<dynamic> variables) {
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if (logStatements) {
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print('[moor_web]: Running $sql with bound args: $variables');
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}
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}
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/// Executes [sql] with the bound [variables], and ignores the result.
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Future _runSimple(String sql, List<dynamic> variables) {
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return _synchronized(() {
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_log(sql, variables);
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_db.runWithArgs(sql, variables);
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});
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}
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Future<void> _runWithoutArgs(String query) {
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return _synchronized(() {
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_db.run(query);
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});
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}
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@override
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Future<void> runCustom(String statement) {
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return _runWithoutArgs(statement);
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}
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@override
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Future<int> runDelete(String statement, List args) {
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_runSimple(statement, args);
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return _handlePotentialUpdate();
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}
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@override
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Future<int> runUpdate(String statement, List args) {
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_runSimple(statement, args);
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return _handlePotentialUpdate();
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}
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@override
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Future<void> runBatched(List<BatchedStatement> statements) async {
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await _synchronized(() {
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for (var stmt in statements) {
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final prepared = _db.prepare(stmt.sql);
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for (var args in stmt.variables) {
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prepared.executeWith(args);
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}
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}
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});
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await _handlePotentialUpdate();
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}
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/// Saves the database if the last statement changed rows. As a side-effect,
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/// saving the database resets the `last_insert_id` counter in sqlite.
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Future<int> _handlePotentialUpdate() {
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final modified = _db.lastModifiedRows();
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if (modified > 0) {
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_storeDb();
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}
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return Future.value(modified);
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}
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@override
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Future<int> runInsert(String statement, List args) async {
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await _runSimple(statement, args);
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final insertId = _db.lastInsertId();
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await _handlePotentialUpdate();
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return insertId;
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}
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@override
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Future<List<Map<String, dynamic>>> runSelect(String statement, List args) {
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_log(statement, args);
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return _synchronized(() async {
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// todo at least for stream queries we should cache prepared statements.
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final stmt = _db.prepare(statement)..executeWith(args);
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List<String> columnNames;
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final rows = <Map<String, dynamic>>[];
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while (stmt.step()) {
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columnNames ??= stmt.columnNames();
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final row = stmt.currentRow();
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rows.add({for (var i = 0; i < row.length; i++) columnNames[i]: row[i]});
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}
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stmt.free();
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return rows;
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});
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}
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}
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/// Experimental moor backend for the web. To use this platform, you need to
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/// include the latest version of `sql.js` in your html.
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class WebDatabase extends QueryExecutor {
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final bool logStatements;
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final String name;
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class WebDatabase extends _DatabaseUser {
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Completer<bool> _openingCompleter;
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SqlJsDatabase _db;
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WebDatabase(this.name, {this.logStatements = false});
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WebDatabase(String name, {bool logStatements = false})
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: super(_DbState(name, logStatements));
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@override
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TransactionExecutor beginTransaction() {
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throw StateError(
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'Transactions are not currently supported with the sql.js backend');
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final transactionReady = Completer<bool>();
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final executor = _TransactionExecutor(_state, transactionReady.future);
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_synchronized(() async {
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// we have the lock -> start the transaction
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transactionReady.complete(true);
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// wait until the transaction is done, then release the lock
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await executor.completed;
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if (executor._needsSave) {
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_storeDb();
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}
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});
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return executor;
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}
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@override
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@ -54,7 +206,7 @@ class WebDatabase extends QueryExecutor {
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final module = await initSqlJs();
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final restored = _restoreDb();
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_db = module.createDatabase(restored);
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_state.db = module.createDatabase(restored);
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if (upgradeNeeded) {
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if (version == null || version < 1) {
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@ -66,110 +218,69 @@ class WebDatabase extends QueryExecutor {
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to: databaseInfo.schemaVersion);
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}
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}
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}
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String get _persistenceKey => 'moor_db_str_$name';
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// todo base64 works, but is very slow. Figure out why bin2str is broken
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Uint8List _restoreDb() {
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final raw = window.localStorage[_persistenceKey];
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if (raw != null) {
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return base64.decode(raw);
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}
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return null;
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}
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void _storeDb() {
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final data = _db.export();
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final binStr = base64.encode(data);
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window.localStorage[_persistenceKey] = binStr;
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}
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@tryInline
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void _log(String sql, List<dynamic> variables) {
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if (logStatements) {
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print('[moor_web]: Running $sql with bound args: $variables');
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}
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}
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/// Executes [sql] with the bound [variables], and ignores the result.
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void _runSimple(String sql, List<dynamic> variables) {
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_log(sql, variables);
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_db.runWithArgs(sql, variables);
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}
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Future<void> _runWithoutArgs(String query) {
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_db.run(query);
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return Future.value(null);
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}
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@override
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Future<void> runCustom(String statement) {
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return _runWithoutArgs(statement);
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}
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@override
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Future<int> runDelete(String statement, List args) {
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_runSimple(statement, args);
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return _handlePotentialUpdate();
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}
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@override
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Future<int> runUpdate(String statement, List args) {
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_runSimple(statement, args);
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return _handlePotentialUpdate();
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}
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@override
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Future<void> runBatched(List<BatchedStatement> statements) async {
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for (var stmt in statements) {
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final prepared = _db.prepare(stmt.sql);
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for (var args in stmt.variables) {
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prepared.executeWith(args);
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}
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}
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await _handlePotentialUpdate();
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}
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/// Saves the database if the last statement changed rows. As a side-effect,
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/// saving the database resets the `last_insert_id` counter in sqlite.
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Future<int> _handlePotentialUpdate() {
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final modified = _db.lastModifiedRows();
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if (modified > 0) {
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_storeDb();
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}
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return Future.value(modified);
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}
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@override
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Future<int> runInsert(String statement, List args) async {
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_runSimple(statement, args);
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final insertId = _db.lastInsertId();
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await _handlePotentialUpdate();
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return insertId;
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}
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@override
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Future<List<Map<String, dynamic>>> runSelect(
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String statement, List args) async {
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_log(statement, args);
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// todo at least for stream queries we should cache prepared statements.
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final stmt = _db.prepare(statement)..executeWith(args);
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List<String> columnNames;
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final rows = <Map<String, dynamic>>[];
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while (stmt.step()) {
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columnNames ??= stmt.columnNames();
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final row = stmt.currentRow();
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rows.add({for (var i = 0; i < row.length; i++) columnNames[i]: row[i]});
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}
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stmt.free();
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return rows;
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await _synchronized(() {
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return databaseInfo.beforeOpenCallback(_BeforeOpenExecutor(_state),
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OpeningDetails(version, databaseInfo.schemaVersion));
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});
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}
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}
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class _BeforeOpenExecutor extends _DatabaseUser {
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_BeforeOpenExecutor(_DbState state) : super(state);
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@override
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final bool _bypassLock = true;
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@override
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TransactionExecutor beginTransaction() {
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throw UnsupportedError(
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"Transactions aren't supported in the before open callback");
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}
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@override
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Future<bool> ensureOpen() => Future.value(true);
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}
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class _TransactionExecutor extends _DatabaseUser
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implements TransactionExecutor {
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_TransactionExecutor(_DbState state, this._openingFuture) : super(state);
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@override
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final bool _bypassLock = true;
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final Future<bool> _openingFuture;
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bool _sentBeginTransaction = false;
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final Completer<void> _completer = Completer();
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Future<void> get completed => _completer.future;
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bool _needsSave = false;
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@override
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void _storeDb() {
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// no-op inside a transaction. Store the database when we it's done!
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_needsSave = true;
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}
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@override
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TransactionExecutor beginTransaction() {
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throw UnsupportedError('Cannot have nested transactions');
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}
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@override
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Future<bool> ensureOpen() async {
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await _openingFuture;
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if (!_sentBeginTransaction) {
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_db.run('BEGIN TRANSACTION');
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_sentBeginTransaction = true;
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}
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return Future.value(true);
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}
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@override
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Future<void> send() {
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_db.run('COMMIT TRANSACTION;');
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_completer.complete();
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return Future.value();
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}
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}
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@ -14,6 +14,7 @@ environment:
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dependencies:
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meta: '>= 1.0.0 <2.0.0'
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collection: '>= 1.0.0 <2.0.0'
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synchronized: ^2.1.0
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dev_dependencies:
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moor_generator: ^1.5.0
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