Postgres - FTS - pg_search - solution to problem with slow rank or weighted search on multiple columns

gistfile1.rb

class AddIndexForFullTextSearch < ActiveRecord::Migration
  def up
    execute "ALTER TABLE users ADD COLUMN tsv tsvector"
    execute <<-QUERY
    UPDATE users SET tsv = (to_tsvector('english', coalesce("building"."first_name"::text, '')) || 
                            to_tsvector('english', coalesce("building"."last_name"::text, '')));
    QUERY
    
    execute "CREATE TRIGGER tsvectorupdate BEFORE INSERT OR UPDATE
              ON users FOR EACH ROW EXECUTE PROCEDURE
              tsvector_update_trigger(tsv, 'pg_catalog.english', first_name, last_name);"
  end
  def down
    execute "drop trigger tsvectorupdate on users"
    execute "alter table users drop column tsv"
  end

gistfile2.rb

class User < ActiveRecord::Base
  include PgSearch
  pg_search_scope :search, against: [:first_name, :last_name], 
    using: {
      tsearch: {
        dictionary: "english",
        tsvector_column: 'tsv'
      }
    }
end