Ecto Migrate

Ecto migrate brings automatic migrations to ecto. Instead of defining and writting manuall diffing from actual model and old model. The ecto_migrate do it for you. It save actual represantation of a model model in database and checks, if actual model have the same format as saved in database.

To test, use EctoIt (is depended on it for tests purposes):

iex -S mix

After, it should be possible:

:application.start(:ecto_it)
alias EctoIt.Repo

import Ecto.Query

defmodule Weather do # is for later at now
  use Ecto.Model

  schema "weather" do
    field :city
    field :temp_lo, :integer
    field :temp_hi, :integer
    field :prcp,    :float, default: 0.0
  end
end

Ecto.Migration.Auto.migrate(Repo, Weather)

%Weather{city: "Berlin", temp_lo: 20, temp_hi: 25} |> Repo.insert
Repo.all(from w in Weather, where: w.city == "Berlin")

Lets redefine the same model in a shell and migrate it

defmodule Weather do # is for later at now
  use Ecto.Model

  schema "weather" do
    field :city
    field :temp_lo, :integer
    field :temp_hi, :integer
    field :prcp,    :float, default: 0.0
    field :wind,    :float, default: 0.0
  end
end

Ecto.Migration.Auto.migrate(Repo, Weather)
Repo.all(from w in Weather, where: w.city == "Berlin")

Lets use references

defmodule Post do
  use Ecto.Model

  schema "posts" do
    field :title, :string
    field :public, :boolean, default: true
    field :visits, :integer
    has_many :comments, Comment
  end
end

defmodule Comment do
  use Ecto.Model

  schema "comments" do
    field :text, :string
    belongs_to :post, Post
  end
end

Ecto.Migration.Auto.migrate(Repo, Post)
Ecto.Migration.Auto.migrate(Repo, Comment)

ecto_migrate also provides additional migrate/3 API. For using with custom source defined models. Example:

defmodule Taggable do
  use Ecto.Model

  schema "this is not a valid schema name and it will never be used" do
    field :tag_id, :integer
  end
end

defmodule MyModel do
  use Ecto.Model
  schema "my_model" do
    field :a, :string
    has_many :my_model_tags, {"my_model_tags", Taggable}, [foreign_key: :tag_id]
  end
end

Now we can migrate my_model_tags table with:

Ecto.Migration.Auto.migrate(Repo, MyModel)
Ecto.Migration.Auto.migrate(Repo, Taggable, [for: MyModel])

It will generate and migrate my_model_tags table to the database which will be associated with my_model table.

Indexes

ecto_migrate has support of indexes:

defmodule Weather do # is for later at now
  use Ecto.Model
  use Ecto.Migration.Auto.Index

  index(:city, unique: true)
  index(:prcp)
  schema "weather" do
    field :city
    field :temp_lo, :integer
    field :temp_hi, :integer
    field :prcp,    :float, default: 0.0
  end
end

If you do not want to use DSL for defining indexes, macro index doing no more, as generate function:

defmodule Weather do # is for later at now
  use Ecto.Model

  schema "weather" do
    field :city
    field :temp_lo, :integer
    field :temp_hi, :integer
    field :prcp,    :float, default: 0.0
  end

  def __indexes__ do
    [{[:city], [unique: true]},
     {[:prpc], []}]
  end
end

Extra attribute options

defmodule Weather do # is for later at now
  use Ecto.Model
  use Ecto.Migration.Auto.Index

  schema "weather" do
    field :city
    field :temp_lo, :integer
    field :temp_hi, :integer
    field :prcp,    :float, default: 0.0
  end

  def __attribute_option__(:city), do: [size: 40]
  def __attribute_option__(_),     do: []
end

Possibility to have more sources

If the same model used by different sources, it is possible to define callback for it

defmodule Weather do # is for later at now
  use Ecto.Model
  use Ecto.Migration.Auto.Index

  schema "weather" do
    field :city
    field :temp_lo, :integer
    field :temp_hi, :integer
    field :prcp,    :float, default: 0.0
  end

  def __sources__, do: ["weather", "history_weather"]
end

Upgrades in 0.3.x versions

If you have installed version before 0.3.2, use 0.3.2 or 0.3.3 for upgrading the table, after that it is possible to upgrade higher versions.