code: private void createUniqueIndexGFS(DBCollection coll, String id)
      {
          try
          {
              coll.createIndex(new BasicDBObject("metadata." + id, 1), new BasicDBObject("unique", true));
          }
          catch (MongoException ex)
          {
              throw new KunderaException("Error in creating unique indexes in " + coll.getFullName() + " collection on "
                      + id + " field");
          }
      }
docs: Creates the unique index gfs.
  
  @param coll
  the coll
  @param id
  the id