title: Filter in grid with custom renderer
body: <p>I have a problem with filter in my module in admin grid.</p>
  
  <p>My problem is:
  Filter for columns with custom renderer not working.</p>
  
  <pre class="lang-php prettyprint-override"><code>public function _prepareColumns()
      {
          $this-&gt;addColumn('entity_id', array(
              'header' =&gt; 'ID',
              'index'  =&gt; 'entity_id',
              'width'  =&gt; '30px'
          ));
          $this-&gt;addColumn('author', array(
              'header'   =&gt; 'Author',
              'index'    =&gt; 'author',
              'renderer' =&gt; 'Test_Block_Adminhtml_Vj_Renderer_Author'
          ));
  </code></pre>
  
  <p>renderer is</p>
  
  <pre class="lang-php prettyprint-override"><code>class Test_Block_Adminhtml_Vj_Renderer_Author extends Mage_Adminhtml_Block_Widget_Grid_Column_Renderer_Abstract
  {
      public function render(Varien_Object $row)
      {
          $value = $row-&gt;getData($this-&gt;getColumn()-&gt;getIndex());
          $autor = Mage::getModel('test/test')-&gt;load($value);
          return ($author-&gt;getName() . ' ' . $author-&gt;getSurname());
      }
   }
  </code></pre>
  
  <p>Author in grid is showing fine for example 'George Bush', but if i try write to filter (for example 'Bu') filter return zero row. :-/</p>
  
  <p>Any idea?
  Thx.</p>