sequel_boom.rb

require 'sequel'
require 'securerandom'

db_host = 'localhost'
db_name = 'test'
db_user = 'root'

db_options = {test: true, max_connections: 10, encoding: 'UTF-8'}

if defined?(JRuby)
  DB = Sequel.connect(
    "jdbc:postgresql://#{db_host}/#{db_name}?user=#{db_user}",
    db_options
  )
else
  DB = Sequel.connect("postgres://#{db_user}@#{db_host}/#{db_name}", db_options)
end

puts 'Preparing...'

DB.create_table!(:reviews) do
  primary_key :id

  String :title, null: false
end

DB.create_table!(:review_comments) do
  String  :comment
  Integer :review_id
end

class Review < Sequel::Model
end

class ReviewComment < Sequel::Model
end

100.times do
  rid = DB[:reviews].insert(:title => SecureRandom.hex)

  DB[:review_comments].insert(:comment => SecureRandom.hex, :review_id => rid)
end

stop = false

puts 'Starting threads...'

%w{INT TERM}.each do |signal|
  trap(signal) do
    stop = true
  end
end

threads = 10.times.map do
  Thread.new do
    loop do
      break if stop

      review = Review.select(:id).order { random{} }.first

      review.update(:title => SecureRandom.hex)

      DB.transaction(savepoint: true) do
        ReviewComment.where(:review_id => review.id).delete
      end

      DB.transaction(savepoint: true) do
        ReviewComment.insert(:review_id => review.id, :comment => SecureRandom.hex)
      end
    end
  end
end

threads.each(&:join)