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

P.S. Tested with Ecto 0.12.0-rc, Postgrex 0.8.4 and PostgreSQL 9.4

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.Binary
  @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
    Binary.decode %TypeInfo{info | send: "hstore_send"}, bin, types, opts
  end

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

Hi I was wondering if you have any idea how to get the hstore column type working in a migration?
I'd like to add a column in a migration:
add :attrs, :hstore

Adding in the above Ecto type and Postgrex extension don't seem to spill over into working with a migration, unless I'm missing something?
Thanks

@gaxunil This worked for me on Ecto 1.1.3

alter table(:some_table) do
  add :metadata, :hstore, default: fragment(~s(''::hstore))
end

Note that you'll need to execute ~s(CREATE EXTENSION IF NOT EXISTS "hstore") in a separate migration if you haven't done so already

stopped working when I upgraded postgrex to 0.11 mainly because Postgrex.Extensions.Binary was deprecated.

• https://gist.github.com/pufe/688ae59881a8f9845549e0c3d5958ecf updated version for postgrex 0.11.2