elixir - How to use raw sql with ecto Repo

Question

I have an upsert requirement, so I need to call a postgres stored procedure or use a common table expression. I also use the pgcrypto exgtension for passwords and would like to use postgres functions (such as "crypt" to encode/decode passwords).

But I can not find a way to get Ecto to play with raw sql in part or whole, is it intended that ecto will only support the elixir dsl and not allow shelling out to raw sql when the dsl is not sufficient?

I've found that I can query via the adapter (Rocket is the name of the app)

q = Ecto.Adapters.Postgres.query(Rocket.Repo,"select * from users limit 1",[])

But not sure how to get this to the model. I'm new to elixir and it seems I should be able to use Ecto.Model.Schem.schema/3 but this fails

Rocket.User.__schema__(:load,q.rows |> List.first,0)
** (FunctionClauseError) no function clause matching in Rocket.User.__schema__/3    

Answer 1

On Ecto 2.0 (beta) with Postgres, you can use Ecto.Adapters.SQL.query() (current docs, 2.0-beta2 docs) to execute arbitrary SQL; in addition to a list of the rows themselves ("rows"), it happens to return a list of column names ("columns").

In the below example, I

1. run a custom query with no parameters,
2. convert the result's column names from strings to atoms, and
3. combine those with each row of the results and map it into a struct with Kernel.struct()

(You'll probably want to run the query() version (without the bang !) and check for {ok, res}.)

qry = "SELECT * FROM users"
res = Ecto.Adapters.SQL.query!(Repo, qry, []) # a

cols = Enum.map res.columns, &(String.to_atom(&1)) # b

roles = Enum.map res.rows, fn(row) ->
  struct(MyApp.User, Enum.zip(cols, row)) # c
end