earth_box in ActiveRecord

CreateExtensionsForDb.rb

# Migration to add cube and earthdistance extensions.
class CreatePostgresExtensions < ActiveRecord::Migration
  def up
    ActiveRecord::Base.connection.execute("CREATE EXTENSION cube;")
    ActiveRecord::Base.connection.execute("CREATE EXTENSION earthdistance;")
  end

  def down
    ActiveRecord::Base.connection.execute("DROP EXTENSION earthdistance;")
    ActiveRecord::Base.connection.execute("DROP EXTENSION cube;")
  end
end

postgres_ar_example.rb

# This requires the postgres-contrib package(This is preinstalled if you installed postgres via homebrew)
# See the migration below to enable these functions.

# == Parameters:
# @lat = Float8
# @lon = Float8
# The third parameter for ll_to_earth is the radius of your selection in meters.
# == Returns:
# An Array containing the matching results.

City.where("earth_box( ll_to_earth(#{lat}, #{lon}), 5000) @> ll_to_earth(latitude, longitude)")