Migrations

Migration Generator Primer

Tasks

The available tasks are:

• mix ash_sqlite.generate_migrations
• mix ash_sqlite.create
• mix ash_sqlite.drop

AshSqlite is built on top of ecto, so much of its behavior is pass-through/orchestration of that tooling.

Basic Workflow

• Make resource changes
• Run mix ash_sqlite.generate_migrations to generate migrations and resource snapshots
• Run mix ash_sqlite.migrate to run those migrations

For more information on generating migrations, see the module documentation here: Mix.Tasks.AshSqlite.GenerateMigrations , or run mix help ash_sqlite.generate_migrations

For running your migrations, there is a mix task that will find all of the repos configured in your apis and run their migrations. It is a thin wrapper around mix ecto.migrate . Ours is called mix ash_sqlite.migrate

If you want to run or rollback individual migrations, use the corresponding

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 ecto.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_sqlite.generate_migrations

# Run migrations if flag
if echo $* | grep -e "-m" -q
then
  mix ecto.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 . If you would like the migrations to automatically run after regeneration, add the -m flag: ./regen.sh -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
    apis()
    |> Enum.flat_map(fn api ->
      api
      |> Ash.Api.Info.resources()
      |> Enum.map(&AshSqlite.repo/1)
    end)
    |> Enum.uniq()
  end

  defp apis do
    Application.fetch_env!(:my_app, :ash_apis)
  end

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