a4.rb

class City < ActiveRecord::Base
	include PgSearch

	belongs_to :region
	belongs_to :country
	has_many   :city_aliases

	##
	# Search against a single field is not so expensive,
	##
	pg_search_scope :cheap_search,
		against: :name,
		ignoring: :accents,
		ranked_by: ":tsearch * log(GREATEST(CAST(population AS integer), 3))",
		order_with_rank: 'pg_search_rank DESC'

	##
	# Search against associated fields will produce join queries
	##
	pg_search_scope :expensive_search,
		against: { name: 'A' },
		associated_against: {
			city_aliases: { name: 'B' },
			region:       { name: 'C' },
			country:      { name: 'D' }
		},
		ignoring: accents,
		ranked_by: ":tsearch * log(GREATEST(CAST(population AS integer), 3))",
		order_with_rank: 'pg_search_rank DESC'
end