migrations-and-tasks.md

Migrations

Tasks

Ash comes with its own tasks, and AshMysql exposes lower level tasks that you can use if necessary. This guide shows the process using ash.* tasks, and the ash_mysql.* tasks are illustrated at the bottom.

Basic W## Basic Workflow

• Make resource changes
• Run mix ash.codegen --name add_a_combobulator to generate migrations and resource snapshots
• Run mix ash.migrate to run those migrations

For more information on generating migrations, run mix help ash_mysql.generate_migrations (the underlying task that is called by mix ash.migrate)

Regenerating Migratio### Regenerating Migrations

Often, you will run into a situation where you want to make a slight change to a resource after you've already generated and run migrations. If you are using git and would like to undo those changes, then regenerate the migrations, this script may prove useful:

#!/bin/bash

# Get count of untracked migrations
N_MIGRATIONS=$(git ls-files --others priv/repo/migrations | wc -l)

# Rollback untracked migrations
mix ash_mysql.rollback -n $N_MIGRATIONS

# Delete untracked migrations and snapshots
git ls-files --others priv/repo/migrations | xargs rm
git ls-files --others priv/resource_snapshots | xargs rm

# Regenerate migrations
mix ash.codegen --name $1

# Run migrations if flag
if echo $* | grep -e "-m" -q
then
  mix ash.migrate
fi

After saving this file to something like regen.sh, make it executable with chmod +x regen.sh. Now you can run it with ./regen.sh name_of_operation. If you would like the migrations to automatically run after regeneration, add the -m flag: ./regen.sh name_of_operation -m.

Multiple Repos

If you are using multiple repos, you will likely need to use mix ecto.migrate and manage it separately for each repo, as the options would be applied to both repo, which wouldn't make sense.

Running Migrations in Production

Define a module similar to the following:

defmodule MyApp.Release do
  @moduledoc """
  Houses tasks that need to be executed in the released application (because mix is not present in releases).
  """
  @app :my_ap
  def migrate do
    load_app()

    for repo <- repos() do
      {:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :up, all: true))
    end
  end

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

  defp repos do
    domains()
    |> Enum.flat_map(fn domain ->
      domain
      |> Ash.Domain.Info.resources()
      |> Enum.map(&AshMysql.repo/1)
    end)
    |> Enum.uniq()
  end

  defp domains do
    Application.fetch_env!(:my_app, :ash_domains)
  end

  defp load_app do
    Application.load(@app)
  end
end

AshMysql-specific tasks

• mix ash_mysql.generate_migrations
• mix ash_mysql.create
• mix ash_mysql.migrate
• mix ash_mysql.rollback
• mix ash_mysql.drop