title: HINT: No function matches the given name and argument types. You might need to add explicit type casts. TrigramSimilarity Django
body: <p>I am trying full text search using <code>TrigramSimilarity</code>. I have activated  <code>pg_trgm</code> extension in PostgreSQL. and added <code>django.contrib.postgres</code> in my installed apps. But when I am trying query</p>
  
  <pre><code>blog.objects.annotate(similarity=TrigramSimilarity('name', 'abc'),).filter(similarity__gt=0.3).order_by('-similarity')
  </code></pre>
  
  <p>But its giving me an error</p>
  
  <blockquote>
    <p>psycopg2.ProgrammingError: function similarity(character varying, unknown) does not exist
        LINE 1: ...others_2", "blog_mod", SIMILARITY...
                                                   ^
        HINT:  No function matches the given name and argument types. You might need to add explicit type casts.</p>
  </blockquote>
  
  <p>Why this error is happening. Please help me.</p>