title: QueryDSL and SQL Function from Postgres
body: <p>I would like to use Postgres FullText search with QueryDsl JPA.</p>
  
  <p>Generated in SQL:</p>
  
  <pre><code>select * 
  from film 
  where to_tsquery ('tarzan') @@ to_tsvector('french',film.title) = true
  </code></pre>
  
  <p>to get all film containing tarzan in their title.</p>
  
  <p>In JPA I define a custom function 'ftsMatch' which I could use like that:</p>
  
  <pre><code>String jpql = "select film from Film film where ftsMatch(:queryString, film.titre) = true";
  </code></pre>
  
  <p>I QueryDSL I would like to have an opportunity to define a predicate on String type :</p>
  
  <pre><code>QFilm.film.titre.ftsMatch('tarzan')
  </code></pre>
  
  <p>I haven't found any solution</p>