core/Mysql.php
public function rollBack()
    {
        if (--$this->transactionCounter) {
            $this->exec('ROLLBACK TO trans' . ($this->transactionCounter + 1));
            return true;
        }
        return $this->pdo->rollBack();
    }
public function rollBack()
    {
        if (--$this->transactionCounter) {
            $this->exec('ROLLBACK TO trans' . ($this->transactionCounter + 1));
            return true;
        }
        return $this->pdo->rollBack();
    }
回滚事务
@return bool
@throws MysqlException