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

``` elixir
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