Get a rough count on the number of records in a postgres table via active record.

estimate_count.rb

module  EstimateCount
  extend ActiveSupport::Concern

  module ClassMethods

    def estimate_count
      sql = "SELECT reltuples FROM pg_class WHERE relname = '#{self.table_name}'"
      query = self.connection.execute(sql)
      if result = query.first
        ("%f" % result['reltuples']).to_i
      end

    end

  end
end