Hi all!

I don’t know what to do to make Ecto happy to run the following query:

 sql = "" <>
   "SELECT chat_user_notification_keys.key " <>
   "FROM chat_user_rooms " <>
   "JOIN chat_user_notification_keys ON chat_user_notification_keys.user_id = chat_user_rooms.user_id " <>
   "JOIN users                       ON users.id = chat_user_rooms.user_id " <>
   "JOIN chat_rooms                  ON chat_rooms.id = chat_user_rooms.room_id " <>
   "WHERE chat_rooms.id_ref = $1::text::uuid " <>
   "  AND users.slug NOT IN ($2)"

 case Ecto.Adapters.SQL.query(BusChatWeb.Repo, sql, [room_id, user_slugs_who_are_present]) do
   {:ok, %{num_rows: num_keys, rows: keys}} ->
     case num_keys do
       0 -> # ...
       _ -> # ...
     end
 end

Currently, I get the following error message:

** (ArgumentError) Postgrex expected a binary, got []. Please make sure the value you are passing matches the definition in your table or in your query or convert the value accordingly.
[debug] QUERY ERROR db=9.9ms
SELECT chat_user_notification_keys.key FROM chat_user_rooms JOIN chat_user_notification_keys ON chat_user_notification_keys.user_id = chat_user_rooms.user_id JOIN users                       ON users.id = chat_user_rooms.user_id JOIN chat_rooms                  ON    chat_rooms.id = chat_user_rooms.room_id WHERE chat_rooms.id_ref = $1::text::uuid   AND users.slug NOT IN ($2) ["afe13f89-7819-43d9-9bb8-b4ba38a2ddac", []]
            (ecto) /Users/francois/Projects/chat_web/deps/postgrex/lib/postgrex/type_module.ex:717: Ecto.Adapters.Postgres.TypeModule.encode_params/3
        (postgrex) lib/postgrex/query.ex:45: DBConnection.Query.Postgrex.Query.encode/3
    (db_connection) lib/db_connection.ex:1071: DBConnection.describe_run/5
    (db_connection) lib/db_connection.ex:1142: anonymous fn/4 in DBConnection.run_meter/5
    (db_connection) lib/db_connection.ex:1199: DBConnection.run_begin/3
    (db_connection) lib/db_connection.ex:584: DBConnection.prepare_execute/4
            (ecto) lib/ecto/adapters/postgres/connection.ex:93: Ecto.Adapters.Postgres.Connection.execute/4
            (ecto) lib/ecto/adapters/sql.ex:243: Ecto.Adapters.SQL.sql_call/6
        (chat_web) lib/chat_web/repo.ex:117: ChatWeb.Repo.find_notifiable_keys/2

The problem is related to the $2 parameter: it’s a list in Elixir-land. How can I convert/cast a list to something Ecto will be happy?

Thanks!