Track Ecto Migrations

Here's how to create, apply and rollback db migrations with ecto.

List all ecto migrations

mix ecto.migrations

Gives something like:

mix ecto.migrations

Repo: BookStore.Repo

  Status    Migration ID    Migration Name
--------------------------------------------------
  ...
  up        20260107001015  my_other_migration
  up        20260115213050  my_migration_name

Generate an ecto migration

When you have new changes you want to make to your database schema, you create a migration file to track those changes:

mix ecto.gen.migration my_migration_name

This will give you a scaffold something like this file, priv/repo/migrations/20260115213050_my_migration_name.exs:

defmodule BookStore.MyMigrationName do
  use Ecto.Migration

  def change do
    # for you to fill in.
  end
end

Or if you have a cool framework like Ash, it'll generate migration content for you based on the definition of the domain's resources:

mix ash_postgres.generate_migrations my_migration_name

This will generate a migration with the appropriate alter, drop calls, etc.

Run ecto migrations

To apply your migration to the database, run:

mix ecto.migrate

Migrate down or rollback

If you want to reverse what you just migrated, you can migrate down, reverse course, and go the other direction.

To roll back just the latest migration, choose -n 1:

mix ecto.rollback -n 1

Permanently remove a migration

Only change or remove migrations that you haven't deployed to prod. Migrations are generally meant to comply to a roll-forward type strategy. We make changes upon our previous changes, but we don't go backward.

But in dev, you might have a reason to change or permanently remove a migration.

First rollback the migration, as above, then remove the /priv/repo/migrations/my_migration_name.exs file. Then gen new migrations and migrate, and you'll be good.