how to create database on release

Questions & Help Questions
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3

@LostKobrakai I have a release that is deployed on various environments - dev, staging etc.. so it is necessary for me to have them created automatically on boot

here is my final code which worked well (also when having configuration in run time release.exs)

defmodule Release.Tasks do
  @moduledoc false

  @start_apps [:postgrex, :ecto, :ecto_sql]

  @myapps [:my_app]
  
  def create_and_migrate() do
    createdb()
    migrate()
  end

  def createdb do
    # Start postgrex and ecto
    IO.puts "Starting dependencies..."

    # Start apps necessary for executing migrations
    Enum.each(@start_apps, &Application.ensure_all_started/1)

    Enum.each(@myapps, &create_db_for/1)
    IO.puts "createdb task done!"

  end

  def create_db_for(app) do
    for repo <- get_repos(app) do
      :ok = ensure_repo_created(repo)
    end
  end

  defp ensure_repo_created(repo) do
    IO.puts "create #{inspect repo} database if it doesn't exist"
    case repo.__adapter__.storage_up(repo.config) do
      :ok -> :ok
      {:error, :already_up} -> :ok
      {:error, term} -> {:error, term}
    end
  end


  def migrate() do
    IO.puts "Start running migrations.."
    Enum.each(@myapps, &run_migrations_for/1)
    IO.puts "migrate task done!"
  end

  def run_migrations_for(app) do
    IO.puts "Running migrations for '#{app}'"
    for repo <- get_repos(app) do
      {:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :up, all: true))
    end
    IO.puts "Finished running migrations for '#{app}'"
  end

  defp get_repos(app) do
    Application.load(app)
    Application.fetch_env!(app, :ecto_repos)
  end

  def rollback(repo, version) do
    {:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :down, to: version))
  end

end