I currently use the following in one of my projects:

defmodule MyApp.Release.Seeder do
  @moduledoc """
  Release tasks for seeds.
  """

  require Logger

  @app :my_app

  @doc """
  Seed seeds file for repo.
  """
  @spec seed(Ecto.Repo.t(), String.t()) :: :ok | {:error, any()}
  def seed(repo, filename) do
    load_app()

    case Ecto.Migrator.with_repo(repo, &eval_seed(&1, filename)) do
      {:ok, {:ok, _fun_return}, _apps} ->
        :ok

      {:ok, {:error, reason}, _apps} ->
        Logger.error(reason)
        {:error, reason}

      {:error, term} ->
        IO.warn(term, [])
        {:error, term}
    end
  end

  @spec eval_seed(Ecto.Repo.t(), String.t()) :: any()
  defp eval_seed(repo, filename) do
    seeds_file = get_path(repo, "seeds", filename)

    if File.regular?(seeds_file) do
      {:ok, Code.eval_file(seeds_file)}
    else
      {:error, "Seeds file not found."}
    end
  end

  @spec get_path(Ecto.Repo.t(), String.t(), String.t()) :: String.t()
  defp get_path(repo, directory, filename) do
    priv_dir = "#{:code.priv_dir(@app)}"

    repo_underscore =
      repo
      |> Module.split()
      |> List.last()
      |> Macro.underscore()

    Path.join([priv_dir, repo_underscore, directory, filename])
  end

  @spec load_app() :: :ok | {:error, term()}
  defp load_app(), do: Application.load(@app)
end

And then for the release:

• bin/my_app eval 'MyApp.Release.Seeder.seed(Elixir.MyApp.Repo, "seed.exs")

PS: You probably need to add to your config.exs

config :my_app, MyApp.Repo,
  start_apps_before_migration: [:logger]

/some_release/bin/prod eval "MyApp.Seeder.start_items" assuming you are using releases

Following Deploying with Releases — Phoenix v1.8.8 for migrations I got stuck when it comes to the seeds due to the fact that they by consensus live in a script .exs which I assumed requires the mix tool to the mix runex.

Ah cool. Even better Can you briefly annotate how that invoking would look like, I did find its full path via priv_dir(:appname) function but didn’t figure out how to run the script itself.

defmodule Appname.Release do
  def run_seeds do
      # Load seeds.exs script here
  end
end