view_benchmark.rb

CONFIDENCE_THRESHOLD = 4

# A user with some attempts
user = User.find(12481)

Benchmark.ips do |x|
  x.report("in ruby") do
    Flashcard.
      all.
      map { |q| q.most_recent_attempt_for(user) }.
      select { |a| a.confidence > 0 && a.confidence < CONFIDENCE_THRESHOLD }.
      map(&:flashcard)
  end

  x.report("in views") do
    LatestAttempt.by(user).
      confidence_below(CONFIDENCE_THRESHOLD).
      includes(:flashcard).
      map(&:flashcard)
  end

  x.compare!
end

# Comparison:
#   in views: 1793.6 i/s
#   in ruby:    21.1 i/s - 85.11x slower