title: How can django sql queries use case insensitive and contains at the same time?
body: <p>Suppose I have two users with username 'AbA' and 'aBa' in the database.
  My query word is 'ab'.</p>
  
  <p>I used </p>
  
  <p><code>User.objects.filter(username__contains='ab')</code> </p>
  
  <p>and</p>
  
  <p><code>User.objects.filter(username__iexact='ab')</code></p>
  
  <p>These two queries get empty result. However, I want to use something like <code>username__contains__iexact='ab'</code> that can retrieve both 'AbA' and 'aBa'.</p>
  
  <p>Anyone know how to resolve this problem? Thanks.</p>