how to get multiple records from db and put into array or map - arrays

Question

I want to get multiple records from db and put into array or map.
this is my sample array with user ids
{"array":[133,136,137] }
this is my code
def array(conn, %{"array" => array}) do
userlist = %{}
Enum.each(array, fn(x) ->
Map.put(userlist, x, Repo.get(ApiDb.User, x))
end)
json conn, userlist
end
but this method return empty array
below is the console output

Answer 1

I think this approach is more optimized than #Dogbert's one (correct me if I'm wrong) because we ask directly Ecto to format each row in tuple then we convert the list of tuples into a map using the built-in Enum.into/2. For that, you'll want to import Ecto.Query in your current module and :
query = from user in ApiDb.User,
where: user.id in ^user_ids,
select: {user.id, user}
Repo.all(query) |> Enum.into(%{})
which yields
%{id1 => user1, id2 => user2...}
For the Poison encoding problem, I didn't encounter any problem regarding the conversion of number keys, as they get converted into strings automatically by Poison.
Hope this also helps :)

Answer 2

You cannot modify the value of a variable outside Enum.each from within Enum.each. For this specific case, I'd use a for to iterate through the list, fetch the user, and put it in a map with the id as key:
def array(conn, %{"array" => array}) do
users = for x <- array, into: %{}, do: {"#{x}", Repo.get(ApiDb.User, x)}
json conn, users
end
I'd suggest using id IN _ query here so that all the records are fetched in a single query:
def array(conn, %{"array" => array}) do
users = from(u in ApiDb.User, where: u.id in ^array) |> Repo.all
map = for user <- users, into: %{}, do: {"#{user.id}", user}
json conn, map
end