Yesod/Persistent one-to-one query

Question

Say, in Yesod/Persistent, I have models setup like so:

User
    ident Text
    password Text Maybe
    UniqueUser ident
Question
    title Text
    asker UserId          


        

Answer 1

How about:

questions <- runDB $ selectList [QuestionTitle !=. ""] [LimitTo 10]
let askerIds = map (\(Entity _ q) -> questionAsker q) questions
askers <- runDB $ selectList [UserId <-. askerIds] []
let questionsAndAskers = zip questions askers

That seems like it should hit the DB once for the users.

Answer 2

I haven't type-checked this yet, but I would stick the whole thing inside of runDB:

runDB $ selectList [QuestionTitle !=. ""] [LimitTo 10] >>= mapM (\qe@(Entity _ q) -> do
    asker <- get $ questionAsker q
    return (qe, asker))