Try updating a portion of a yaml file

update_yaml.rb

f = File.open("./example.yaml", "w")
100000.times do |n|
  str = "user_#{n}:\n  id: #{n}\n  score: 0\n"
  File.write("./example.yaml", str, mode: "a")
end

def find_position(target, file_obj)
  file_obj.pos = file_obj.read =~ Regexp.new(target)
end

def update_user(name, params)
  file = File.new("./example.yaml")
  char_pos = find_position(name, file)
  new_str = 3.times.with_object("") do |_, str|
    str << file.readline
  end
  params.each do |k, v|
    attr_line = Regexp.new(k.to_s + ".+$")
    new_str.sub!(attr_line, "#{k}: #{v}")
  end
  File.write("./example.yaml", new_str, char_pos)
end

require 'yaml'

def modify_user(name, params)
  users_info = YAML.load_file("./example.yaml")
  user = users_info[name]
  params.each do |k, v|
    user[k.to_s] = v
  end
  File.open("./example.yaml", "w") do |f|
    f.write(YAML.dump(users_info))
  end
end

def change_user(name, params)
  users_info = YAML.load_file("./example.yaml")
  user_info = users_info[name]
  params.each do |k, v|
    user_info[k.to_s] = v
  end
  pos = find_position(name, File.open("./example.yaml"))
  user_hash = { name => user_info }
  File.write("./example.yaml", YAML.dump(user_hash).sub("---\n", ""), pos)
end

start = Time.new
update_user("user_500000", score: 9)
over = Time.new
duration = over - start
p duration

start = Time.new
modify_user("user_500000", score: 8)
over = Time.new
duration = over - start
p duration

start = Time.new
change_user("user_500000", score: 7)
over = Time.new
duration = over - start
p duration