Laravel Eloquent 在不同的连接上预先加载

Question

I am trying to use Laravel Eloquent ORM to do a simple one to one relationship on two different connections.

Let say I do :

MyModel::on('secondary_connection')->get()

That is working fine.

When I do :

MyModel::on('secondary_connection')->with('AnotherModel')->get();

I am getting an error because eloquent is doing the AnotherModel SELECT statement on the default connection (instead of "secondary_connection").

I can't find a way to work this around.

My models are well defined since I can join them in my default connection.

Thoughts ?

Answer 1

Well, as I've been suggested by many users, it seems that there's no way to do this on the fly. My understanding of this is that Eloquent is incomplete when comes to manage multi-connection.

There's 2 way to work this around I could figure.

First, specify the connection in the model :

class MyModel {
    $protected connection = 'secondary_connection';
}

That is obviously a bad workaround since this model is only usable in one connection... but still works.

Then, as Jarek Tkaczyk suggested, it is possible to switch de default connection with the new one. But instead of doing it in the config file, it is possible to swap the PDO oject.

    $default = DB::getPdo(); // Default conn
    $secondary = DB::connection('secondary_connection')->getPdo();
    DB::setPdo($secondary);
    $result = MyModel::with('AnotherModel')->get();
    DB::setPdo($default);

That is a workaround that works and can be a clean solution. Next step is to put that switching mechanism in a nice Laravel way.

Answer 2

There's literally no way to do it on the fly.

You need to alter the default connection in order to make Eloquent use it for the eager loaded models. You can wrap it in a helper method like this:

function on($connection, Closure $callback)
{
    // backup default connection
    $default = Config::get('database.default');

    // change for current query
    Config::set('database.default', $connection);

    // run the query
    $result = $callback();

    // restore the default connection
    Config::set('database.default', $default);

    return $result;
}

then just call like below:

$models = on('secondary_connection', function () {
   return MyModel::with('relation')->get();
});

Answer 3

I ended up with replacing the simply relationship functions with a bit more custom onces. For instance my ->relatedModel is somewhat of a copy of the original in the Eloquent Model, but includes setting the connection:

public function relatedModel() {
  $instance = new \relatedModel;
  $instance->setConnection($this->getConnectionName());
  $query = $instance->newQuery();

  return new BelongsTo($query, $this, 'myForeignKey', $instance->getKeyName(), null);
}

I'm on Laravel 5, so maybe this is different to 4.2.

And since I was fiddling around with this issue a lot now here is a great way to get Validation done over another connection than the default: http://laravel.io/forum/10-29-2014-validation-rules-and-multiple-db-connections

If it is a model method, you can even shorten it down to:

$v = Validator::make($data, $rules);
$v->getPresenceVerifier()->setConnection($this->getConnectionName());

Answer 4

I also am dealing with this issue. I found a solution but it will only work if it is acceptable to configure the used connection through the .env file. This will not work if you want to change it dynamically although you could in that case use a bit of logic (call a function) to return the correct connection name.

The solution I have is to override the connectionName method of the Model class. In my case I have a base class for all my models that takes care of this:

abstract class ModelBase extends Model
{
    public function getConnectionName()
    {
        return env('ELOQUENT_DB_CONNECTION', parent::getConnectionName());
    }
}

As I mentioned you can put whatever logic you want in the getConnectionName so you can make it more dynamic.

Answer 5

class MyModel {
    $protected connection = 'secondary_connection';
}

is the nice option as eloquent models are DB facades + extras. all DB facades functions also apply to eloquent models. therefore instead of changing connection in db facade we can change it here only there is no difference.