bm.rb

require "benchmark/ips"
quiet_logger
c = ActiveRecord::Base.connection
mysql = c.instance_variable_get("@connection")
sql = "select * from users where id = 1"

Benchmark.ips do |x|
  x.time = 5
  x.warmup = 0.1

  x.report("ActiveRecord::Base") do
    User.find(1)
  end
  x.report("Connection query") do
    c.execute(sql)
  end
  x.report("No ActiveRecord") do
    mysql.query(sql)
  end
  x.compare!
end