title: django-pgcrypto-fields taking long time to load
body: <p>I'm using <code>django 2.2.13</code> and <code>django-pgcrypto-fields 2.5.2</code>. Also i'm using <code>email</code> as authentication method. <code>email</code> is stored as <code>pgcrypto</code> field. There are around 10000 active users. When user tries to login it takes a long time (8-9 seconds). I tried to login from shell, it also takes a long time.</p>
  <pre><code>from django.contrib.auth import authenticate
  user = authenticate(email='john@gmail.com', password='secret')
  </code></pre>
  <p>The authenticate function takes almost 7-8 seconds to execute.</p>
  <pre><code>user = authenticate(username='john', password='secret')
  </code></pre>
  <p>When I try to authenticate using <code>username</code>, it executes within 1 seconds</p>
  <pre><code>from app.models import User
  user = User.objects.filter(email=email).first()
  </code></pre>
  <p>The above query also takes a long time to execute (7-8 seconds). I tried indexing the email column, but the outcome is same. How can I speed up authentication and filter queries for pgcrypto fields?</p>