Using Postres hstore with Elixir, Ecto & Postgrex

README.md

To use hstore in Ecto schemas you have to create own Ecto type. To do this, follow these steps:

1. Create files hstore.ex & hstore_extension.ex inside your lib folder
2. Open your database settings and add the following line

extensions: [{MyApp.HStoreExtension, nil}],, for example

config :my_app, MyApp.Repo,
  adapter: Ecto.Adapters.Postgres,
  username: "postgres",
  password: "",
  database: "database_name",
  extensions: [{MyApp.HStoreExtension, nil}],
  size: 100

• On postgrex 0.10 onwards, postgrex split the Binary extension across multiple files, so this fork uses the Postgrex.Extensions.HStore instead of the Postgrex.Extensions.Binary
• Tested with Ecto 2.0.0-rc.6, Postgrex 0.11.2 and PostgreSQL 9.3.5

hstore.ex

defmodule MyApp.HStore do
  @behaviour Ecto.Type

  def type, do: :hstore
  def cast(value), do: {:ok, value}
  def blank?(_), do: false

  def load(value) do
    {:ok, value}
  end

  def dump(value) do
    {:ok, value}
  end
end

hstore_extension.ex

defmodule MyApp.HStoreExtension do
  alias Postgrex.TypeInfo
  alias Postgrex.Extensions.HStore
  @behaviour Postgrex.Extension

  def init(_parameters, _opts), do: []

  def matching(_), do: [type: "hstore"]

  def format(_), do: :binary

  def decode(info = %TypeInfo{type: "hstore"}, bin, types, _opts) do
    HStore.decode %TypeInfo{info | send: "hstore_send"}, bin, types, :reference # can also use :copy
  end

  def encode(info = %TypeInfo{type: "hstore"}, map, types, opts) do
    HStore.encode %TypeInfo{info | send: "hstore_send"}, map, types, opts
  end
end