title: Adding data to Magento grid collection destroys pager
body: <p>in my own Magento Extension I'm using a grid block, to display the collection of data in my db table. Everything works fine so far and the standard pagination from magento works, too.</p>
  
  <p>I now want to add some random data, which isn't in the db table, to the collection to show it in my grid. If I try as follow the pagination stops working:</p>
  
  <pre><code>class My_own_Block_Admin_Main_Grid extends Mage_Adminhtml_Block_Widget_Grid
  {
      protected function _prepareCollection {
  
           // Load the collection
           $collection = getResourceModel('sales/order_grid_collection');
  
           // Add custom data
           $collection-&gt;addToAll('example', 'This is a test');
  
           // Set the collection
           $this-&gt;setCollection($collection);
           return parent::_prepareCollection();   
      }
  }
  </code></pre>
  
  <p>The pagination is effectless now. Page 1 is the same as 2 and shows all entries.</p>
  
  <p>What's the right and working way to a data to the collection without breaking the pagination?</p>