Change source to Phalcon\Mvc\Model\Query\Builder

For such database juggling you'd need PDO-only approach I guess.

Do I understand correctly - you want to perform the join between tables in different databases?

That's what it seems. And database is bound to the connection itself, so even with PDO like in my example:

 private final function _connect(){
        $init = [\PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES UTF8'];
        $this->pdo = new \PDO("mysql:host={$this->db->connection->default->host};dbname={$this->db->connection->default->dbname};", $this->db->connection->default->username, $this->db->connection->default->password, $init);
        $this->pdo->setAttribute(\PDO::ATTR_ERRMODE, \PDO::ERRMODE_EXCEPTION);
        $this->pdo->setAttribute(\PDO::ATTR_DEFAULT_FETCH_MODE, \PDO::FETCH_OBJ);
        $this->pdo->setAttribute(\PDO::ATTR_CASE, \PDO::CASE_UPPER);
    }

You'd need to have two separate PDO connections etc. And for that you need custom method specific to your use case of joining two databases.

Sorry, I guess I was not clear. what I need is to run the same query in different databases, but not between different database tables. I found a reasonable solution. All databases have the same structure, and all my Models are using a "ConnectionService" called db_client. So I'm storing the settings for each database in CliDI()->setShared('client_name'). So for every database I change the setting of "db_client" like this:

$diCli = $this->getDI();
$diCli->setShared('db_client', $diCli->getShared($cliente));

Thanks!

Yeah, that was clear now :)

But in general, application should not be providing fail over capabilities of such kind in case of a DB downtime. Load balancers in front of DB should take care of such events. Thus, your app targets one single point of entry, no matter what node might go down in the background.