require 'benchmark'
require 'active_record'

# $ docker run --rm -p 5432:5432 -e POSTGRES_PASSWORD=password -d postgres:9.6
# $ psql -h localhost -U postgres -d postgres
ActiveRecord::Base.establish_connection(
  adapter: 'postgresql',
  encoding: 'unicode',
  host: 'localhost',
  database: 'postgres',
  username: 'postgres',
  password: 'password',
)

MEMBER_SIZE = 100
KEYS = Array.new(MEMBER_SIZE, &:to_s)
VALUE = 'a' * 100

Type = Struct.new('Type', *KEYS)

ActiveRecord::Base.connection.create_table(:benchmark, id: false, force: true) do |t|
  MEMBER_SIZE.times { |i| t.string i.to_s }
end

class Model < ActiveRecord::Base
  self.table_name = 'benchmark'
end

hash = KEYS.each_with_object({}) { |k, m| m[k] = VALUE }
struct = Type.new(*KEYS)
ar = Model.new(hash)

N = 100_000
Benchmark.bm(20) do |x|
  x.report('Hash') do
    N.times do
      KEYS.each { |key| hash[key] }
    end
  end

  x.report('Struct') do
    N.times do
      KEYS.each { |key| struct[key] }
    end
  end

  x.report('ActiveRecord') do
    N.times do
      KEYS.each { |key| ar[key] }
    end
  end
end

SIZE = 10_000

puts ''
puts '### Array<Hash> 10,000'
puts ''
puts `ps u #{$$}`
array_hash = Array.new(SIZE) { KEYS.each_with_object({}) { |k, m| m[k] = VALUE } }
puts `ps u #{$$}`
puts ''
puts '### Array<Struct> 10,000'
puts ''
puts `ps u #{$$}`
array_struct = Array.new(SIZE) { Type.new(*KEYS) }
puts `ps u #{$$}`
puts ''
puts '### Array<ActiveRecord::Base> 10,000'
puts ''
puts `ps u #{$$}`
array_ar = Array.new(SIZE) { Model.new(hash) }
puts `ps u #{$$}`

__END__

ruby 2.5.3p105 (2018-10-18 revision 65156) [x86_64-linux]

                           user     system      total        real
Hash                   1.055541   0.000745   1.056286 (  1.057475)
Struct                 1.994870   0.002425   1.997295 (  2.003269)
ActiveRecord           8.106248   0.009364   8.115612 (  8.150399)

### Array<Hash> 10,000

USER       PID  %CPU %MEM      VSZ    RSS   TT  STAT STARTED      TIME COMMAND
koshigoe 35281 100.0  0.6  4506992  99012   ??  Ss    7:32AM   0:11.53 benchmark-hash-vs-struct-vs-ar.rb
USER       PID  %CPU %MEM      VSZ    RSS   TT  STAT STARTED      TIME COMMAND
koshigoe 35281 100.0  0.8  4505968 138700   ??  Ss    7:32AM   0:11.88 benchmark-hash-vs-struct-vs-ar.rb

### Array<Struct> 10,000

USER       PID  %CPU %MEM      VSZ    RSS   TT  STAT STARTED      TIME COMMAND
koshigoe 35281 100.0  0.8  4505968 138700   ??  Ss    7:32AM   0:11.89 benchmark-hash-vs-struct-vs-ar.rb
USER       PID  %CPU %MEM      VSZ    RSS   TT  STAT STARTED      TIME COMMAND
koshigoe 35281 100.0  0.9  4520304 146052   ??  Ss    7:32AM   0:11.90 benchmark-hash-vs-struct-vs-ar.rb

### Array<ActiveRecord::Base> 10,000

USER       PID  %CPU %MEM      VSZ    RSS   TT  STAT STARTED      TIME COMMAND
koshigoe 35281 100.0  0.9  4520304 146052   ??  Ss    7:32AM   0:11.90 benchmark-hash-vs-struct-vs-ar.rb
USER       PID  %CPU %MEM      VSZ    RSS   TT  STAT STARTED      TIME COMMAND
koshigoe 35281 100.0  2.5  4788280 412972   ??  Ss    7:32AM   0:18.81 benchmark-hash-vs-struct-vs-ar.rb