On Fri, Dec 26, 2014 at 10:52:46AM +0000, Tom Ellis wrote:
On Fri, Dec 26, 2014 at 02:36:07PM +1100, Riaan wrote:
So went back to HDBC. But now my queries are starting to get fairly long and I have been looking at libraries like Persistent with Esqualeto, HaskellDB and Groundhog to make my queries a little more composable and type safe.
Don't forget to look at Opaleye too :) It doesn't really have much support for arrays at the moment, but if you let me know what you want to do I'm happy to help you.
So to my question. Does anyone have experience with one of these libraries in dealing with postgresql arrays
postgresql-simple has
instance (FromField a, Typeable a) => FromField (PGArray a)
Does that not do exactly what you want?
import Database.PostgreSQL.Simple (query_, ConnectInfo(..), connect, Only) import Database.PostgreSQL.Simple.Types (PGArray) import Data.String (fromString) connectInfo :: ConnectInfo connectInfo = ConnectInfo { connectHost = "localhost" , connectPort = 25433 , connectUser = "tom" , connectPassword = "tom" , connectDatabase = "opaleye_test" } arrayQuery :: String arrayQuery = "select '{{1,2}, {3,4}}' :: integer[][]" main :: IO () main = do conn <- connect connectInfo results <- query_ conn (fromString arrayQuery) :: IO [Only (PGArray (PGArray Int))] print results -- Output -- -- ghci> main -- [Only {fromOnly = PGArray {fromPGArray = [PGArray {fromPGArray = [1,2]},PGArray {fromPGArray = [3,4]}]}}]