Postgresql GREATEST squeel example

pg_greatest.rb

require 'squeel'

# Say a Farm has two integers to keep track of its stock and a constant to define what the minimum number of animals is
class Farm < ActiveRecord::Base
  MIN_ANIMALS = 10
  attr_accessible :kitten_count, :unicorn_count
end

# Now I want to bring back the largest count of animals for each farm, with the minimum value being MIN_ANIMALS incase both are below 10
Farm.select{ op('GREATEST', [kitten_count, unicorn_count, MIN_ANIMALS).as{ total_animal_count } }
# Does not work :C