Q3.

The problem right now is due to N+1 queries, which means, our database is being flooded with 1, 000, 000 + 1 queries (Since we have a million subscriptions currently)—this is because Ruby on Rails lazy loading enabled by default. So to improve this, we eager load all the subscription entity with ‘includes()’. This allows to preload the plan associated data and thereby saving us some time. There are also other ways to eager load subscription entity with ‘eager_load()’ and ‘preload()’.

# lib/scripts/output_subscribers.rb

puts "email,monthly_price"

Subscription.includes(:plan).where.not(plans: {id: nil}).find_each do |subscription|

  puts "#{subscription.email},#{subscription.plan.monthly_price}"

end