# `SquatchMail.Migrations`
[🔗](https://github.com/Axio-Intelligence/Squatch-Mail/blob/v0.1.0/lib/squatch_mail/migrations.ex#L1)

Versioned migrations for SquatchMail's database tables.

SquatchMail keeps its tables isolated in their own Postgres schema (the
`:prefix`, `"squatch_mail"` by default) inside the host application's database.
Rather than shipping raw, hand-editable migrations, all schema changes are
applied through this single, versioned entrypoint — the same pattern used by
Oban and ErrorTracker.

## Usage

The host application generates one migration that delegates here:

    defmodule MyApp.Repo.Migrations.AddSquatchMail do
      use Ecto.Migration

      def up, do: SquatchMail.Migrations.up()
      def down, do: SquatchMail.Migrations.down()
    end

Then runs it with `mix ecto.migrate`. Later SquatchMail releases add new
versions; the host generates another migration pinned to a version:

    def up, do: SquatchMail.Migrations.up(version: 2)
    def down, do: SquatchMail.Migrations.down(version: 1)

## Options

  * `:prefix` - the Postgres schema to create the tables in. Defaults to
    `SquatchMail.Config.prefix/0` (`"squatch_mail"`).
  * `:version` - the version to migrate to. Defaults to the latest version.
  * `:create_schema` - whether to `CREATE SCHEMA IF NOT EXISTS` for the
    prefix. Defaults to `true`. Set to `false` when the schema is managed
    externally or when the prefix is `"public"`.

The applied version is tracked as a `COMMENT` on the `emails` table (mirroring
Oban, which comments `oban_jobs`), so re-running `up/1` is idempotent and only
the outstanding versions run.

# `down`

```elixir
@spec down(Keyword.t()) :: :ok
```

Rolls SquatchMail's tables back down to the given version (default `0`).

# `migrated_version`

```elixir
@spec migrated_version(Keyword.t()) :: non_neg_integer()
```

Returns the currently-migrated version for the given prefix (0 if none).

# `up`

```elixir
@spec up(Keyword.t()) :: :ok
```

Migrates SquatchMail's tables up to the given (or latest) version.

---

*Consult [api-reference.md](api-reference.md) for complete listing*