title: I want know the rank in a Django queryset
body: <p>I have a product list model and would like to know the ranking of a specific price of this model.</p>
  
  <pre><code>sorted_product_list = Product.objects.all().order_by('-price')
  my_product = {'id': 10, 'price': 20000}
  </code></pre>
  
  <p>django has <code>RowNum</code> class but it is not support for mysql
  i have only one idea that use <code>enumerate</code></p>
  
  <pre><code>for rank, element in enumerate(sorted_product_list):
      if element.id == my_product.id:
          my_product_rank = rank
  </code></pre>
  
  <p>Is there any other solution?</p>