title: Remove infrequent words from ts_vector in postgres full text search
body: <p>Is it possible to make postgres to_tsvector  consider only words which occur more than N times in the table? </p>
  
  <p>The only option I am seeing is to calculate the word frequencies myself beforehand and then construct a dictionary out of that list which replaces each with empty string. Is there any more elegant solution in the configurations ?</p>