Registry vs :pg

Section

defmodule RegistryTest do
  def init() do
    {:ok, _} =
      Registry.start_link(
        keys: :duplicate,
        name: Registry.PubSubTest,
        partitions: System.schedulers_online()
      )
  end

  def subscribe_pid(pid) do
    {:ok, _} = Registry.register(Registry.PubSubTest, "hello", pid)
  end

  def send_message(message) do
    Registry.dispatch(Registry.PubSubTest, "hello", fn entries ->
      for {pid, _} <- entries, do: send(pid, :hello)
    end)
  end
end

pid1 =
  spawn(fn ->
    receive do
      :hello -> IO.puts("world")
    end
  end)

pid2 =
  spawn(fn ->
    receive do
      :hello -> IO.puts("ocean")
    end
  end)

pid3 =
  spawn(fn ->
    receive do
      :hello -> IO.puts("sky")
    end
  end)