使用phalcon时，我有两个数据库，如何在使用modelsManager的$builder之前选择一个数据库？

return [
    'db' => [
        'db1' => [
            'adapter'  => 'Mysql',
            'host'     => 'localhost',
            'username' => 'db1_user',
            'password' => 'db1_password',
            'dbname'   => 'db1_name',
        ],
        'db2' => [
            'adapter'  => 'Mysql',
            'host'     => 'localhost',
            'username' => 'db2_user',
            'password' => 'db2_password',
            'dbname'   => 'db2_name',
        ],
    ],
];

use Phalcon\Mvc\Model\Query\Builder;

// 设置要使用的数据库连接
$modelsManager->setConnectionService('db1');

// 创建查询构建器对象
$builder = $modelsManager->createBuilder();