Enhances Ecto.Schema modules to track a full history of changes.

The versioned_schema macro works just like schema in Ecto.Schema but it also builds an OriginalModule.Version schema module as well to represent a version at a particular point in time.

In addition to options allowed by Ecto.Schema, new ones are also allowed.

Additional belongs_to Options

• :versioned - If true, the version schema will include an extra field of the same name but with _version appended. The parent record which existed when this version was created can be loaded into this field via Versioned.preload/2.

Example:

versioned_schema "people" do
  belongs_to :car, Car, type: :binary_id, versioned: true
end

Additional has_many Options

• :versioned - If true, the version schema will include an extra field of the same name but with _version appended. If defined as another truthy atom, then that field name will be used instead. The child records which existed when this version was created can be loaded into this field via Versioned.preload/2.

Example:

versioned_schema "cars" do
  has_many :people, Person, on_replace: :delete, versioned: :person_versions
end

I already have an integer primary key.

While Versioned generally operates with binary_ids, it is possible to adopt it for an existing table which uses integers. First, you'll need to create a migration to create the versions table. Then, define your own @primary_key attribute. Versioned will preserve it, but note that the versions table must still use UUIDs.

@primary_key {:id, :id, autogenerate: true}
versioned_schema "cars" do
  ...
end

Example

defmodule MyApp.Car do
  use Versioned.Schema

  versioned_schema "cars" do
    field :name, :string
    has_many :people, MyApp.Person, versioned: true
  end
end