race_condition_test.rb

success_count = 0
fail_count = 0

lock = Mutex.new

DB = Application.db

DB.drop_table :race_test rescue nil

DB.create_table :race_test do
  primary_key :id
  Integer :value
end

1_000.times do
  id = DB[:race_test].insert({:value => 0})

  thread1 = Thread.new do
    DB.transaction do
      DB[:race_test].filter(:id => id).update({:value => :value + 1})
    end
  end

  thread2 = Thread.new do
    DB.transaction do
      DB[:race_test].filter(:id => id).update({:value => :value + 10})
    end
  end
  
  thread1.join
  thread2.join

  if DB[:race_test][:id => id][:value] == 11
    lock.synchronize { success_count += 1 }
  else
    lock.synchronize { fail_count += 1 }
  end
end

puts "Failed: #{fail_count}, OK: #{success_count}"