haskell - Getting data out of rawQuery using Conduits

Question

I admit I do not really understand Conduits very well given my limited Haskell knowledge. So appreciate if someone can guide me on how to accomplish this task: I would like to take the output of a rawQuery action and store it in a variable that I can then use again in my Hamlet file. For example:

let sql = "SELECT sum(value) as total, category FROM person GROUP BY category ORDER BY total desc;"
   --- ??  how to store this runDB output in a variable?
runDB $ rawQuery sql [] $$ CL.map (convertFromPersistent) 
where 
    convertFromPersistent [] = Nothing
    convertFromPersistent [PersistInt64 sum,PersistInt64 category] = Just (sum,category)
    convertFromPersistent _ = Nothing

When I do

runDB $ rawQuery sql [] $$ CL.mapM_ (liftIO. print. convertFromPersistent) 

I see the output in the log file. However, I would like to pipe the output to an array of tuples so I can work with it in my Hamlet file. Appreciate your help!

Thanks,

Answer 1

通过反复试验，我发现这是可行的：

res <- runDB $ rawQuery sql [] $$ CL.map (convertFromPersistent) =$ CL.consume