First approach at creating view

create_bikes_report_view.rb

class CreateBikesReportView < ActiveRecord::Migration
  def change
    reversible do |dir|
      dir.up do
        execute(
          <<-QUERY
            CREATE MATERIALIZED VIEW bikes_reports AS
              SELECT
              bikes.name, bikes.model,
              count(rentals.id) as times_rented,
              round(SUM(extract(
                epoch from (rentals.returned_at - rentals.created_at)
              )/ 3600 * bikes.price)::numeric, 2) as revenue
              FROM
              rentals INNER JOIN bikes ON bikes.id = rentals.bike_id
              GROUP BY bikes.id
              ORDER BY times_rented DESC;
          QUERY
        )
      end

      dir.down do
        execute(
          <<-QUERY
          DROP MATERIALIZED VIEW IF EXISTS bikes_reports;
          QUERY
        )
      end
    end

  end
end