Redis vs Lua payload reconstruction

luatime.rb

require 'bundler'

Bundler.setup

require 'json'
require 'benchmark/ips'
require 'redis'
require 'securerandom'

REDIS = Redis.new(url: 'redis://localhost:6379/11')

def gen_post(id)
  auth = JSON.dump(id: id, name: SecureRandom.hex(8))
  post = JSON.dump(id: id, author_id: 3, title: SecureRandom.hex(16))
  comm = JSON.dump(id: id, post_id: id, body: SecureRandom.hex(16))

  { "posts/#{id}" => post, "authors/#{id}" => auth, "comments/#{id}" => comm }
end

def construct_ruby
  hashes = REDIS.multi do
    ('posts/0'..'posts/30').map { |key| REDIS.hgetall(key) }
  end

  array_backed_hash = Hash.new { |hash, key| hash[key] = [] }

  payload = hashes.each_with_object(array_backed_hash) do |hash, memo|
    hash.each do |key, val|
      root, _ = key.split('/')
      memo[root] << val
    end
  end

  payload
end

SCRIPT = <<-LUA
  local payload = {}

  for _, key in ipairs(KEYS) do
    local hash = redis.call('HGETALL', key)

    for index = 1, #hash, 2 do
      local field = hash[index]
      local data  = hash[index + 1]
      local root  = string.gsub(field, '(%a)([/\]%d*)', '%1')

      if type(payload[root]) == "table" then
        table.insert(payload[root], data)
      else
        payload[root] = {data}
      end
    end
  end

  return cjson.encode(payload)
LUA

def construct_lua
  REDIS.evalsha(SHA, ('posts/1'..'posts/30').to_a)
end

REDIS.flushdb
SHA = REDIS.script(:load, SCRIPT)

posts = (1..30).map { |index| gen_post(index) }

posts.each_with_index do |post, index|
  REDIS.hmset("posts/#{index}", post.to_a.flatten)
end

Benchmark.ips do |x|
  x.report('ruby') { construct_ruby }
  x.report('lua')  { construct_lua }
end