Demo of light weight database futures

deferred_query.rb

require 'benchmark'

ENV['RAILS_ENV'] ||= 'development'
require_relative 'config/environment'

class DeferredQuery
  def initialize(query)
    @thread = Thread.new do
      ActiveRecord::Base.connection_pool.with_connection do |connection|
        connection.execute(query)
      end
    end
  end

  def result
    @thread.value
  end
end

count = ActiveRecord::Base.connection_pool.instance_variable_get(:@size) * 2
puts "#{count} queries"

Benchmark.bm do |x|
  query = 'SELECT sleep(1)'

  x.report('sync:') do
    count.times do
      ActiveRecord::Base.connection.execute(query)
    end
  end

  x.report('conc:') do
    futures = []
    count.times do
      futures << DeferredQuery.new(query)
    end
    futures.each {|q| q.result }
  end
end