title: function convert_from(character varying, unknown) does not exist in Postgres
body: <p>When i'm trying to convert from unicode to utf8 in the code below
  <strong>"function convert_from(character varying, unknown) does not exist"</strong> error occurs.</p>
  
  <pre><code>select convert_from(artists, 'UTF8') from songs where     
  to_tsvector('simple',convert_from(artists, 'UTF8')) 
    @@ plainto_tsquery('simple','alizee') 
  limit 100
  </code></pre>
  
  <p>Column "<strong>artists</strong>" has "TEXT" type.</p>
  
  <p>But when I'm running</p>
  
  <pre><code>select convert_from(E'\u0422\u0438\u043c\u0430\u0442\u0438', 'UTF8');
  </code></pre>
  
  <p>it works well.</p>
  
  <p>How can I resolve this problem?
  I would appreciate any help. Thanks</p>