Magento newsletter queue grid recipients column

Question

i am extend the newsletter module in mangento(1.9), in the newsletter queue grid having column name recipients, but in table don't have a column name like that.

May i know from where that field value is coming.

For your further reference i have attached some screen and code in grid file.

in queue grid class
-------------------
  $this->addColumn('subscribers_total', array(
            'header'    =>  Mage::helper('newsletter')->__('Recipients'),
            'type'      => 'number',
            'index'     => 'subscribers_total'
        ));

newsletter_queue table

News letter grid

Answer 1

In Newsletter Queue Grid magento get the collection as below

$collection = Mage::getResourceModel('newsletter/queue_collection')
            ->addSubscribersInfo();

Mage_Adminhtml_Block_Newsletter_Queue_Grid. In the newsletter/queue_collection magento join the newsletter_queue_link table.

You can see the code in Mage_Newsletter_Model_Resource_Queue_Collection

$select = $this->getConnection()->select()
            ->from(array('qlt' => $this->getTable('newsletter/queue_link')), 'COUNT(qlt.queue_link_id)')
            ->where('qlt.queue_id = main_table.queue_id');
        $totalExpr = new Zend_Db_Expr(sprintf('(%s)', $select->assemble()));
        $select = $this->getConnection()->select()
            ->from(array('qls' => $this->getTable('newsletter/queue_link')), 'COUNT(qls.queue_link_id)')
            ->where('qls.queue_id = main_table.queue_id')
            ->where('qls.letter_sent_at IS NOT NULL');
        $sentExpr  = new Zend_Db_Expr(sprintf('(%s)', $select->assemble()));

        $this->getSelect()->columns(array(
            'subscribers_sent'  => $sentExpr,
            'subscribers_total' => $totalExpr
        ));
        return $this;