load_old_values.rb

ENV['RAILS_ENV'] = ARGV[0] || 'production'
DIR = File.dirname(__FILE__)
require DIR + '/config/environment'

class LoadOldValues
  include PricingLogger

  def initialize(realm)
    raise 'invalid realm' unless ["gasco", "enex"].include?(realm)
    @realm = realm
  end

  def attrs
    {
      "id" => :integer,
      "price_id" => :integer,
      "value" => :integer,
      "price_changed_at" => :datetime
    }
  end

  def query
    PriceChange.select(attrs.keys)
               .where(realm: @realm)
               .order(:price_id, :price_changed_at)
               .to_sql
  end

  def update_query(prev_record, current_record)
    prev_value = prev_record[2]
    prev_price_changed_at = prev_record[3].to_datetime.strftime('%Y-%m-%d %H:%M:%S')

    <<~SQL
      UPDATE price_changes
      SET old_value = #{prev_value}, old_price_changed_at = "#{prev_price_changed_at}"
      WHERE id = #{current_record[0]}
    SQL
  end

  def perform
    log_start_proccess
    prev_record = nil
    ActiveRecord::Base.connection.execute(query).each_with_index do |record, idx|
      log_msg(idx) if (idx % 10000).zero?

      if prev_record && prev_record[1] == record[1]
        ActiveRecord::Base.connection.execute(update_query(prev_record, record))
      end

      prev_record = record
    end
  ensure
    log_end_process
  end
end

LoadOldValues.new("enex").perform