So I have extended a Magento collection to obtain my own collection only I want to use a different DB connection. What I have attempted to do is define the connection in config.xml like so:


and then in my overriding constructor, do:

class VMR_Customreports_Model_Resource_Storeoverview_Collection extends     Mage_Reports_Model_Resource_Order_Collection
        public function __construct()

                $resource = Mage::getSingleton('core/resource');
                $conn = $resource->getConnection('externaldb_read');


This doesn't appear to have any effect. I would have expected an error if it didn't work. What do I do?

UPDATE: After more debugging, I note that this code below returns the original db connection and not the one I defined in my XML. Why is that?

$conn = $resource->getConnection('externaldb_read');

  • Is the collection class based on Mage_Core_Model_Resource_Db_Collection_Abstract or Mage_Eav_Model_Entity_Collection_Abstract? – Vinai Nov 26 '13 at 22:25
  • My Collection extends Mage_Reports_Model_Resource_Order_Collection. One sec and I'll try to dig down to see if it extends from either of those. – user2045 Nov 26 '13 at 22:28
  • It extends from Mage_Core_Model_Resource_Db_Collection_Abstract – user2045 Nov 26 '13 at 22:31

A quick check (see test case below) actually shows what you are doing should be just peachy.
For that reason, I suspect some error in your configuration. Please edit your post to include your collection class with at least it's __construct and _construct methods.
Also, if you are not using the sales/order resource model, please include it with it's constructor methods, too.

I just noticed you are using $resource->getConnection('reportingdb_read'); in your constructor.
In the configuration XML the connection is called <externaldb_read>.
Note: reportingdb_read != externaldb_read

Maybe thats just a copy & paste error in your post, but if not, you have to use
If that isn't the issue, please update your post, again, and I'll help dig further.

// Test to confirm a connection set via setConnection() on a 
// Mage_Reports_Model_Resource_Order_Collection instance is used
// to load the collection data.
class Reports_CollectionTest extends PHPUnit_Framework_TestCase
    public static function setUpBeforeClass()
        require_once 'app/Mage.php';

    protected function getConnectionMock()
        $mockSelect = $this->getMockBuilder('Varien_Db_Select')

        $mockConn = $this->getMockBuilder('Varien_Db_Adapter_Pdo_Mysql')



        return $mockConn;

     * @test
    public function testCollectionConnection()
        $mockCon = $this->getConnectionMock();

        $collection = new Mage_Reports_Model_Resource_Order_Collection;

        $this->assertSame($mockCon, $collection->getConnection());
| improve this answer | |
  • I updated my original post to include the whole constructor. As far as I know I am using the sales/order resource model because I am just rewriting the query but still using the order table. If there's something else you need, please let me know. Thank you. – user2045 Nov 26 '13 at 23:34
  • Updated my answer. – Vinai Nov 27 '13 at 6:43
  • Yeah sorry, that isn't the issue. I just didnt copy properly. I updated the OP. Please continue to help me. – user2045 Nov 27 '13 at 16:08
  • Also, having done a bit of debbugging, it looks like my collection's $this->_conn doesn't change upon calling $this->setCollection() – user2045 Nov 27 '13 at 18:06

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