Yii2中的事务
今天运行程序时发现有条数据不完整。出现问题的数据属于某个事务，按道理要么逻辑走完数据提交，要么回滚。出现预料外问题，第一个反应是ActiveRecord中内嵌事务会单独提交到数据库中？为了验证这个问题，抽空写了一个测试用例验证。
准备工作
先建立两个表 foo1 和 foo2：
CREATE TABLE `foo1` ( `id` int(11) NOT NULL PRIMARY KEY AUTO_INCREMENT, `data1` varchar(12) NOT NULL UNIQUE, `value` varchar(32) NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8; CREATE TABLE `foo2` ( `id` int(11) NOT NULL PRIMARY KEY AUTO_INCREMENT, `data2` varchar(12) NOT NULL UNIQUE, `value` varchar(32) NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
创建相应的ActiveRecord类，并定义好规则：
// file: Foo1.php namespace console\models; use yii\db\ActiveRecord; class Foo1 extends ActiveRecord { public function rules() { return [ [["data1", "value"], "required", "on" => [self::SCENARIO_DEFAULT, "other]], ["data1", "string", "length" => [2, 8]], ]; } public function transactions() { return [ self::SCENARIO_DEFAULT => self::OP_ALL, ]; } } // file: Foo2.php namespace console\models; use yii\db\ActiveRecord; class Foo2 extends ActiveRecord { public function rules() { return [ [["data2", "value"], "required"], ["data2", "string", "length" => [2, 8]], ]; } public function transactions() { return [ self::SCENARIO_DEFAULT => self::OP_ALL, ]; } } 编写测试用例
为了彻底搞清楚Yii2中事务的执行情况，总共编写了六个例子。六个示例的作用分别是：
- 非事务保存、数据校验不通过
- 事务保存、数据校验不通过
- 校验通过、多模型数据保存
- 某条数据校验不通过
- 某条数据插入冲突
- 事务执行中exit/return
测试例子的代码如下：
namespace console\controllers; use Yii; use yii\db\Exception; use yii\console\Controller; use console\models\{Foo1, Foo2}; class TestController extends Controller { public function beforeAction($action) { if (parent::beforeAction($action)) { $db = Foo1::getDb(); $db->createCommand("truncate table " . Foo1::tableName())->execute(); $db->createCommand("truncate table " . Foo2::tableName())->execute(); return true; } return false; } public function actionCase1() { $transaction = Yii::$app->db->beginTransaction(); try { $foo1 = new Foo1([ "data1" => "1234567890", "value" => "1245677553", ]); $foo1->scenario = 'other'; $foo1->save(); $transaction->commit(); echo "transaction committed"; } catch (Exception $e) { $transaction->rollback(); echo "insert data error:", $e->getMessage(); } } public function actionCase2() { $transaction = Yii::$app->db->beginTransaction(); try { $foo1 = new Foo1([ "data1" => "1234567890", "value" => "1245677553", ]); $foo1->save(); $transaction->commit(); echo "transaction committed"; } catch (Exception $e) { $transaction->rollback(); echo "insert data error:", $e->getMessage(); } } public function actionCase3() { $transaction = Yii::$app->db->beginTransaction(); try { $foo1 = new Foo1([ "data1" => "12345678", "value" => "1245677553", ]); $foo1->save(); $foo2 = new Foo1([ "data1" => "12345678", "value" => "1245677553", ]); $foo2->save(); $transaction->commit(); echo "transaction committed"; } catch (Exception $e) { $transaction->rollback(); echo "insert data error:", $e->getMessage(); } } public function actionCase4() { $transaction = Yii::$app->db->beginTransaction(); try { $foo1 = new Foo1([ "data1" => "12345678", "value" => "1245677553", ]); $foo1->save(); $foo2 = new Foo2([ "data2" => "1234567890", "value" => "1245677553", ]); $foo2->save(); $transaction->commit(); echo "transaction committed"; } catch (Exception $e) { $transaction->rollback(); echo "insert data error:", $e->getMessage(); } } public function actionCase5() { $transaction = Yii::$app->db->beginTransaction(); try { $foo1 = new Foo1([ "data1" => "12345678", "value" => "1245677553", ]); $foo1->save(); $foo2 = new Foo2([ "data2" => "12345678", "value" => "1245677553", ]); $foo2->save(); $foo2 = new Foo2([ "data2" => "12345678", "value" => "1245677553", ]); $foo2->save(); $transaction->commit(); echo "transaction committed"; } catch (Exception $e) { $transaction->rollback(); echo "insert data error:", $e->getMessage(); } } public function actionCase6() { $transaction = Yii::$app->db->beginTransaction(); echo "transaction level:", $transaction->level, PHP_EOL; try { $foo1 = new Foo1([ "data1" => "12345678", "value" => "1245677553", ]); $foo1->save(); echo "exit now"; exit; $transaction->commit(); } catch (Exception $e) { $transaction->rollback(); echo "insert data error:", $e->getMessage(); } } } 执行结果
依次执行上述测试用例，结果如下：
- case1: 输出”transaction committed”，数据未插入；
- case2: 输出”transaction committed”，数据未插入；
- case3: 输出”insert data error:SQLSTATE[23000]: Integrity constraint violation:1062 Duplicate entry ‘12345678’ for key ‘data1’ The SQL being executed was: INSERT INTO
foo1(data1,value) VALUES (‘12345678’, ‘1245677553’)”，数据未插入； - case4: 输出”transaction committed”，foo1中的数据成功插入；
- case5: 输出”insert data error:SQLSTATE[23000]: Integrity constraint violation:1062 Duplicate entry ‘12345678’ for key ‘data2’ The SQL being executed was: INSERT INTO
foo2(data2,value) VALUES (‘12345678’, ‘1245677553’)”，数据未插入； - case6: 输出”exit now”，数据未插入。
分析
大部分示例的结果在预料之中，震惊的是case2和case4的结果。之前一直以为只要包裹在事务中，并且在transactions方法中声明了所在场景启用事务，数据保存出错就会抛异常，数据回滚。这个测试彻底颠覆了我的认知。
为了搞清楚执行机制，开始跟踪Yii2执行数据保存的源码。首先查看ActiveRecord基类BaseActiveRecord中的save方法：
public function save($runValidation = true, $attributeNames = null) { if ($this->getIsNewRecord()) { return $this->insert($runValidation, $attributeNames); } else { return $this->update($runValidation, $attributeNames) !== false; } } save方法根据是否新数据，走插入或更新流程。继续跟踪insert方法（定义在yii\db\ActiveRecord中）：
public function insert($runValidation = true, $attributes = null) { if ($runValidation && !$this->validate($attributes)) { Yii::info('Model not inserted due to validation error.', __METHOD__); return false; } if (!$this->isTransactional(self::OP_INSERT)) { return $this->insertInternal($attributes); } $transaction = static::getDb()->beginTransaction(); try { $result = $this->insertInternal($attributes); if ($result === false) { $transaction->rollBack(); } else { $transaction->commit(); } return $result; } catch (\Exception $e) { $transaction->rollBack(); throw $e; } catch (\Throwable $e) { $transaction->rollBack(); throw $e; } } insert方法的实现代码解决了我的疑问：数据的规则验证不通过，直接返回false，不会抛异常。
再看保存过程：如果当前场景未声明事务，常规保存；事务保存第一步还是尝试常规保存，如果失败，回滚并抛出异常；如果事务保存成功，提交事务。
到这一步，Yii中事务处理已经比较清晰了。剩下的问题是：嵌套事务如何处理？继续跟踪yii\db\Transaction中的commit方法：
public function commit() { if (!$this->getIsActive()) { throw new Exception('Failed to commit transaction: transaction was inactive.'); } $this->_level--; if ($this->_level === 0) { Yii::trace('Commit transaction', __METHOD__); $this->db->pdo->commit(); $this->db->trigger(Connection::EVENT_COMMIT_TRANSACTION); return; } $schema = $this->db->getSchema(); if ($schema->supportsSavepoint()) { Yii::trace('Release savepoint ' . $this->_level, __METHOD__); $schema->releaseSavepoint('LEVEL' . $this->_level); } else { Yii::info('Transaction not committed: nested transaction not supported', __METHOD__); } } 代码中出现事务的层级（level），结合begin方法，每嵌套一层事务，level加一并创建savepoint。事务提交时，如果是最外层事务，直接提交到数据库；如果是内嵌事务，释放savepoint或什么都不做。所以嵌套事务的疑问也解决了：内嵌事务不会单独提交。
总结
通过这次测试和源码跟踪阅读，对Yii的事务了解又深入一步。最大的收获是：事务开始前调用validate方法先校验数据，无错误时再通过事务中调用save(false)方法插入数据，此时出错才会抛出异常。
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