{-# LANGUAGE OverloadedStrings #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE FlexibleContexts #-} -- | A MySQL backend for @persistent@. module Database.Persist.MySQL ( withMySQLPool , withMySQLConn , createMySQLPool , module Database.Persist , module Database.Persist.GenericSql , MySQL.ConnectInfo(..) , MySQLBase.SSLInfo(..) , MySQL.defaultConnectInfo , MySQLBase.defaultSSLInfo , MySQLConf(..) ) where import Control.Arrow import Control.Monad (mzero) import Control.Monad.IO.Class (MonadIO (..)) import Control.Monad.Trans.Class (lift) import Control.Monad.Trans.Error (ErrorT(..)) import Data.Aeson import Data.ByteString (ByteString) import Data.Either (partitionEithers) import Data.Function (on) import Data.IORef import Data.List (find, intercalate, sort, groupBy) import Data.Text (Text, pack) -- import Data.Time.LocalTime (localTimeToUTC, utc) import System.Environment (getEnvironment) import qualified Data.Conduit as C import qualified Data.Conduit.List as CL import qualified Data.Map as Map import qualified Data.Text as T import qualified Data.Text.Encoding as T import Database.Persist hiding (Entity (..)) import Database.Persist.Store import Database.Persist.GenericSql hiding (Key(..)) import Database.Persist.GenericSql.Internal import Database.Persist.EntityDef import qualified Database.MySQL.Simple as MySQL import qualified Database.MySQL.Simple.Param as MySQL import qualified Database.MySQL.Simple.Result as MySQL import qualified Database.MySQL.Simple.Types as MySQL import qualified Database.MySQL.Base as MySQLBase import qualified Database.MySQL.Base.Types as MySQLBase -- | Create a MySQL connection pool and run the given action. -- The pool is properly released after the action finishes using -- it. Note that you should not use the given 'ConnectionPool' -- outside the action since it may be already been released. withMySQLPool :: MonadIO m => MySQL.ConnectInfo -- ^ Connection information. -> Int -- ^ Number of connections to be kept open in the pool. -> (ConnectionPool -> m a) -- ^ Action to be executed that uses the connection pool. -> m a withMySQLPool ci = withSqlPool $ open' ci -- | Create a MySQL connection pool. Note that it's your -- responsability to properly close the connection pool when -- unneeded. Use 'withMySQLPool' for automatic resource control. createMySQLPool :: MonadIO m => MySQL.ConnectInfo -- ^ Connection information. -> Int -- ^ Number of connections to be kept open in the pool. -> m ConnectionPool createMySQLPool ci = createSqlPool $ open' ci -- | Same as 'withMySQLPool', but instead of opening a pool -- of connections, only one connection is opened. withMySQLConn :: C.ResourceIO m => MySQL.ConnectInfo -- ^ Connection information. -> (Connection -> m a) -- ^ Action to be executed that uses the connection. -> m a withMySQLConn = withSqlConn . open' -- | Internal function that opens a connection to the MySQL -- server. open' :: MySQL.ConnectInfo -> IO Connection open' ci = do conn <- MySQL.connect ci MySQLBase.autocommit conn False -- disable autocommit! smap <- newIORef $ Map.empty return Connection { prepare = prepare' conn , stmtMap = smap , insertSql = insertSql' , close = MySQL.close conn , migrateSql = migrate' ci , begin = const $ MySQL.execute_ conn "start transaction" >> return () , commitC = const $ MySQL.commit conn , rollbackC = const $ MySQL.rollback conn , escapeName = pack . escapeDBName , noLimit = "LIMIT 18446744073709551615" -- This noLimit is suggested by MySQL's own docs, see -- } -- | Prepare a query. We don't support prepared statements, but -- we'll do some client-side preprocessing here. prepare' :: MySQL.Connection -> Text -> IO Statement prepare' conn sql = do let query = MySQL.Query (T.encodeUtf8 sql) return Statement { finalize = return () , reset = return () , execute = execute' conn query , withStmt = withStmt' conn query } -- | SQL code to be executed when inserting an entity. insertSql' :: DBName -> [DBName] -> Either Text (Text, Text) insertSql' t cols = Right (doInsert, "SELECT LAST_INSERT_ID()") where doInsert = pack $ concat [ "INSERT INTO " , escapeDBName t , "(" , intercalate "," $ map escapeDBName cols , ") VALUES(" , intercalate "," (map (const "?") cols) , ")" ] -- | Execute an statement that doesn't return any results. execute' :: MySQL.Connection -> MySQL.Query -> [PersistValue] -> IO () execute' conn query vals = MySQL.execute conn query (map P vals) >> return () -- | Execute an statement that does return results. The results -- are fetched all at once and stored into memory. withStmt' :: C.ResourceIO m => MySQL.Connection -> MySQL.Query -> [PersistValue] -> C.Source m [PersistValue] withStmt' conn query vals = C.sourceIO (liftIO openS ) (liftIO . closeS) (liftIO . pullS ) where openS = do -- Execute the query MySQLBase.query conn =<< MySQL.formatQuery conn query (map P vals) result <- MySQLBase.storeResult conn -- Find out the type of the columns fields <- MySQLBase.fetchFields result let getters = [ maybe PersistNull (getGetter (MySQLBase.fieldType f) f . Just) | f <- fields] -- Ready to go! return (result, getters) closeS (result, _) = MySQLBase.freeResult result pullS (result, getters) = do row <- MySQLBase.fetchRow result case row of [] -> MySQLBase.freeResult result >> return C.IOClosed _ -> return $ C.IOOpen $ zipWith ($) getters row -- | @newtype@ around 'PersistValue' that supports the -- 'MySQL.Param' type class. newtype P = P PersistValue instance MySQL.Param P where render (P (PersistText t)) = MySQL.render t render (P (PersistByteString bs)) = MySQL.render bs render (P (PersistInt64 i)) = MySQL.render i render (P (PersistDouble d)) = MySQL.render d render (P (PersistBool b)) = MySQL.render b render (P (PersistDay d)) = MySQL.render d render (P (PersistTimeOfDay t)) = MySQL.render t render (P (PersistUTCTime t)) = MySQL.render t render (P PersistNull) = MySQL.render MySQL.Null render (P (PersistList l)) = MySQL.render $ listToJSON l render (P (PersistMap m)) = MySQL.render $ mapToJSON m render (P (PersistObjectId _)) = error "Refusing to serialize a PersistObjectId to a MySQL value" -- | @Getter a@ is a function that converts an incoming value -- into a data type @a@. type Getter a = MySQLBase.Field -> Maybe ByteString -> a -- | Helper to construct 'Getter'@s@ using 'MySQL.Result'. convertPV :: MySQL.Result a => (a -> b) -> Getter b convertPV f = (f .) . MySQL.convert -- | Get the corresponding @'Getter' 'PersistValue'@ depending on -- the type of the column. getGetter :: MySQLBase.Type -> Getter PersistValue -- Bool getGetter MySQLBase.Tiny = convertPV PersistBool -- Int64 getGetter MySQLBase.Int24 = convertPV PersistInt64 getGetter MySQLBase.Short = convertPV PersistInt64 getGetter MySQLBase.Long = convertPV PersistInt64 getGetter MySQLBase.LongLong = convertPV PersistInt64 -- Double getGetter MySQLBase.Float = convertPV PersistDouble getGetter MySQLBase.Double = convertPV PersistDouble getGetter MySQLBase.Decimal = convertPV PersistDouble getGetter MySQLBase.NewDecimal = convertPV PersistDouble -- Text getGetter MySQLBase.VarChar = convertPV persistText getGetter MySQLBase.VarString = convertPV persistText getGetter MySQLBase.String = convertPV persistText -- ByteString getGetter MySQLBase.Blob = convertPV PersistByteString getGetter MySQLBase.TinyBlob = convertPV PersistByteString getGetter MySQLBase.MediumBlob = convertPV PersistByteString getGetter MySQLBase.LongBlob = convertPV PersistByteString -- Time-related getGetter MySQLBase.Time = convertPV PersistTimeOfDay getGetter MySQLBase.DateTime = convertPV PersistUTCTime getGetter MySQLBase.Timestamp = convertPV PersistUTCTime getGetter MySQLBase.Date = convertPV PersistDay getGetter MySQLBase.NewDate = convertPV PersistDay getGetter MySQLBase.Year = convertPV PersistDay -- Null getGetter MySQLBase.Null = \_ _ -> PersistNull -- Controversial conversions getGetter MySQLBase.Set = convertPV PersistText getGetter MySQLBase.Enum = convertPV PersistText -- Unsupported getGetter other = error $ "MySQL.getGetter: type " ++ show other ++ " not supported." persistText :: ByteString -> PersistValue persistText = PersistText . T.decodeUtf8 ---------------------------------------------------------------------- -- | Create the migration plan for the given 'PersistEntity' -- @val@. migrate' :: PersistEntity val => MySQL.ConnectInfo -> [EntityDef] -> (Text -> IO Statement) -> val -> IO (Either [Text] [(Bool, Text)]) migrate' connectInfo allDefs getter val = do let name = entityDB $ entityDef val old <- getColumns connectInfo getter $ entityDef val let new = second (map udToPair) $ mkColumns allDefs val case (old, partitionEithers old) of -- Nothing found, create everything ([], _) -> do let addTable = AddTable $ concat [ "CREATE TABLE " , escapeDBName name , "(" , escapeDBName $ entityID $ entityDef val , " BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY" , concatMap (\x -> ',' : showColumn x) $ fst new , ")" ] let uniques = flip concatMap (snd new) $ \(uname, ucols) -> [ AlterTable name $ AddUniqueConstraint uname $ map (findTypeOfColumn allDefs name) ucols ] let foreigns = do Column cname _ _ _ _ (Just (refTblName, _)) <- fst new return $ AlterColumn name (cname, addReference allDefs refTblName) return $ Right $ map showAlterDb $ addTable : uniques ++ foreigns -- No errors and something found, migrate (_, ([], old')) -> do let (acs, ats) = getAlters allDefs name new $ partitionEithers old' acs' = map (AlterColumn name) acs ats' = map (AlterTable name) ats return $ Right $ map showAlterDb $ acs' ++ ats' -- Errors (_, (errs, _)) -> return $ Left errs -- | Find out the type of a column. findTypeOfColumn :: [EntityDef] -> DBName -> DBName -> (DBName, FieldType) findTypeOfColumn allDefs name col = maybe (error $ "Could not find type of column " ++ show col ++ " on table " ++ show name ++ " (allDefs = " ++ show allDefs ++ ")") ((,) col) $ do entDef <- find ((== name) . entityDB) allDefs fieldDef <- find ((== col) . fieldDB) (entityFields entDef) return (fieldType fieldDef) -- | Helper for 'AddRefence' that finds out the 'entityID'. addReference :: [EntityDef] -> DBName -> AlterColumn addReference allDefs name = AddReference name id_ where id_ = maybe (error $ "Could not find ID of entity " ++ show name ++ " (allDefs = " ++ show allDefs ++ ")") id $ do entDef <- find ((== name) . entityDB) allDefs return (entityID entDef) data AlterColumn = Change Column | Add Column | Drop | Default String | NoDefault | Update String | AddReference DBName DBName | DropReference DBName type AlterColumn' = (DBName, AlterColumn) data AlterTable = AddUniqueConstraint DBName [(DBName, FieldType)] | DropUniqueConstraint DBName data AlterDB = AddTable String | AlterColumn DBName AlterColumn' | AlterTable DBName AlterTable udToPair :: UniqueDef -> (DBName, [DBName]) udToPair ud = (uniqueDBName ud, map snd $ uniqueFields ud) ---------------------------------------------------------------------- -- | Returns all of the 'Column'@s@ in the given table currently -- in the database. getColumns :: MySQL.ConnectInfo -> (Text -> IO Statement) -> EntityDef -> IO [Either Text (Either Column (DBName, [DBName]))] getColumns connectInfo getter def = do -- Find out all columns. stmtClmns <- getter "SELECT COLUMN_NAME, \ \IS_NULLABLE, \ \DATA_TYPE, \ \COLUMN_DEFAULT \ \FROM INFORMATION_SCHEMA.COLUMNS \ \WHERE TABLE_SCHEMA = ? \ \AND TABLE_NAME = ? \ \AND COLUMN_NAME <> ?" inter <- C.runResourceT $ withStmt stmtClmns vals C.$$ CL.consume cs <- C.runResourceT $ CL.sourceList inter C.$$ helperClmns -- avoid nested queries -- Find out the constraints. stmtCntrs <- getter "SELECT CONSTRAINT_NAME, \ \COLUMN_NAME \ \FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE \ \WHERE TABLE_SCHEMA = ? \ \AND TABLE_NAME = ? \ \AND COLUMN_NAME <> ? \ \AND REFERENCED_TABLE_SCHEMA IS NULL \ \ORDER BY CONSTRAINT_NAME, \ \COLUMN_NAME" us <- C.runResourceT $ withStmt stmtCntrs vals C.$$ helperCntrs -- Return both return $ cs ++ us where vals = [ PersistText $ pack $ MySQL.connectDatabase connectInfo , PersistText $ unDBName $ entityDB def , PersistText $ unDBName $ entityID def ] helperClmns = CL.mapM getIt C.=$ CL.consume where getIt = fmap (either Left (Right . Left)) . liftIO . getColumn connectInfo getter (entityDB def) helperCntrs = do let check [PersistText cntrName, PersistText clmnName] = return (cntrName, clmnName) check other = fail $ "helperCntrs: unexpected " ++ show other rows <- mapM check =<< CL.consume return $ map (Right . Right . (DBName . fst . head &&& map (DBName . snd))) $ groupBy ((==) `on` fst) rows -- | Get the information about a column in a table. getColumn :: MySQL.ConnectInfo -> (Text -> IO Statement) -> DBName -> [PersistValue] -> IO (Either Text Column) getColumn connectInfo getter tname [ PersistText cname , PersistText null_ , PersistText type' , default'] = fmap (either (Left . pack) Right) $ runErrorT $ do -- Default value default_ <- case default' of PersistNull -> return Nothing PersistText t -> return (Just t) _ -> fail $ "Invalid default column: " ++ show default' -- Column type type_ <- parseType type' -- Foreign key (if any) stmt <- lift $ getter "SELECT REFERENCED_TABLE_NAME, \ \CONSTRAINT_NAME \ \FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE \ \WHERE TABLE_SCHEMA = ? \ \AND TABLE_NAME = ? \ \AND COLUMN_NAME = ? \ \AND REFERENCED_TABLE_SCHEMA = ? \ \ORDER BY CONSTRAINT_NAME, \ \COLUMN_NAME" let vars = [ PersistText $ pack $ MySQL.connectDatabase connectInfo , PersistText $ unDBName $ tname , PersistText $ cname , PersistText $ pack $ MySQL.connectDatabase connectInfo ] cntrs <- C.runResourceT $ withStmt stmt vars C.$$ CL.consume ref <- case cntrs of [] -> return Nothing [[PersistText tab, PersistText ref]] -> return $ Just (DBName tab, DBName ref) _ -> fail "MySQL.getColumn/getRef: never here" -- Okay! return $ Column (DBName cname) (null_ == "YES") type_ default_ Nothing ref -- FIXME: maxLen getColumn _ _ _ x = return $ Left $ pack $ "Invalid result from INFORMATION_SCHEMA: " ++ show x -- | Parse the type of column as returned by MySQL's -- @INFORMATION_SCHEMA@ tables. parseType :: Monad m => Text -> m SqlType parseType "tinyint" = return SqlBool -- Ints parseType "int" = return SqlInt32 parseType "short" = return SqlInt32 parseType "long" = return SqlInteger parseType "longlong" = return SqlInteger parseType "mediumint" = return SqlInt32 parseType "bigint" = return SqlInteger -- Double parseType "float" = return SqlReal parseType "double" = return SqlReal parseType "decimal" = return SqlReal parseType "newdecimal" = return SqlReal -- Text parseType "varchar" = return SqlString parseType "varstring" = return SqlString parseType "string" = return SqlString parseType "text" = return SqlString parseType "tinytext" = return SqlString parseType "mediumtext" = return SqlString parseType "longtext" = return SqlString -- ByteString parseType "varbinary" = return SqlBlob parseType "blob" = return SqlBlob parseType "tinyblob" = return SqlBlob parseType "mediumblob" = return SqlBlob parseType "longblob" = return SqlBlob -- Time-related parseType "time" = return SqlTime parseType "datetime" = return SqlDayTime parseType "timestamp" = return SqlDayTime parseType "date" = return SqlDay parseType "newdate" = return SqlDay parseType "year" = return SqlDay -- Unsupported parseType other = fail $ "MySQL.parseType: type " ++ show other ++ " not supported." ---------------------------------------------------------------------- -- | @getAlters allDefs tblName new old@ finds out what needs to -- be changed from @old@ to become @new@. getAlters :: [EntityDef] -> DBName -> ([Column], [(DBName, [DBName])]) -> ([Column], [(DBName, [DBName])]) -> ([AlterColumn'], [AlterTable]) getAlters allDefs tblName (c1, u1) (c2, u2) = (getAltersC c1 c2, getAltersU u1 u2) where getAltersC [] old = map (\x -> (cName x, Drop)) old getAltersC (new:news) old = let (alters, old') = findAlters allDefs new old in alters ++ getAltersC news old' getAltersU [] old = map (DropUniqueConstraint . fst) old getAltersU ((name, cols):news) old = case lookup name old of Nothing -> AddUniqueConstraint name (map findType cols) : getAltersU news old Just ocols -> let old' = filter (\(x, _) -> x /= name) old in if sort cols == ocols then getAltersU news old' else DropUniqueConstraint name : AddUniqueConstraint name (map findType cols) : getAltersU news old' where findType = findTypeOfColumn allDefs tblName -- | @findAlters newColumn oldColumns@ finds out what needs to be -- changed in the columns @oldColumns@ for @newColumn@ to be -- supported. findAlters :: [EntityDef] -> Column -> [Column] -> ([AlterColumn'], [Column]) findAlters allDefs col@(Column name isNull type_ def _maxLen ref) cols = case filter ((name ==) . cName) cols of [] -> ( let cnstr = [addReference allDefs tname | Just (tname, _) <- [ref]] in map ((,) name) (Add col : cnstr) , cols ) Column _ isNull' type_' def' _maxLen' ref':_ -> let -- Foreign key refDrop = case (ref == ref', ref') of (False, Just (_, cname)) -> [(name, DropReference cname)] _ -> [] refAdd = case (ref == ref', ref) of (False, Just (tname, _)) -> [(name, addReference allDefs tname)] _ -> [] -- Type and nullability modType | type_ == type_' && isNull == isNull' = [] | otherwise = [(name, Change col)] -- Default value modDef | def == def' = [] | otherwise = case def of Nothing -> [(name, NoDefault)] Just s -> [(name, Default $ T.unpack s)] in ( refDrop ++ modType ++ modDef ++ refAdd , filter ((name /=) . cName) cols ) ---------------------------------------------------------------------- -- | Prints the part of a @CREATE TABLE@ statement about a given -- column. showColumn :: Column -> String showColumn (Column n nu t def maxLen ref) = concat [ escapeDBName n , " " , showSqlType t maxLen , " " , if nu then "NULL" else "NOT NULL" , case def of Nothing -> "" Just s -> " DEFAULT " ++ T.unpack s , case ref of Nothing -> "" Just (s, _) -> " REFERENCES " ++ escapeDBName s ] -- | Renders an 'SqlType' in MySQL's format. showSqlType :: SqlType -> Maybe Integer -- ^ @maxlen@ -> String showSqlType SqlBlob Nothing = "BLOB" showSqlType SqlBlob (Just i) = "VARBINARY(" ++ show i ++ ")" showSqlType SqlBool _ = "TINYINT(1)" showSqlType SqlDay _ = "DATE" showSqlType SqlDayTime _ = "DATETIME" showSqlType SqlInt32 _ = "INT" showSqlType SqlInteger _ = "BIGINT" showSqlType SqlReal _ = "DOUBLE PRECISION" showSqlType SqlString Nothing = "TEXT CHARACTER SET utf8" showSqlType SqlString (Just i) = "VARCHAR(" ++ show i ++ ") CHARACTER SET utf8" showSqlType SqlTime _ = "TIME" -- | Render an action that must be done on the database. showAlterDb :: AlterDB -> (Bool, Text) showAlterDb (AddTable s) = (False, pack s) showAlterDb (AlterColumn t (c, ac)) = (isUnsafe ac, pack $ showAlter t (c, ac)) where isUnsafe Drop = True isUnsafe _ = False showAlterDb (AlterTable t at) = (False, pack $ showAlterTable t at) -- | Render an action that must be done on a table. showAlterTable :: DBName -> AlterTable -> String showAlterTable table (AddUniqueConstraint cname cols) = concat [ "ALTER TABLE " , escapeDBName table , " ADD CONSTRAINT " , escapeDBName cname , " UNIQUE(" , intercalate "," $ map escapeDBName' cols , ")" ] where escapeDBName' (name, (FTTypeCon _ "Text" )) = escapeDBName name ++ "(200)" escapeDBName' (name, (FTTypeCon _ "String" )) = escapeDBName name ++ "(200)" escapeDBName' (name, (FTTypeCon _ "ByteString")) = escapeDBName name ++ "(200)" escapeDBName' (name, _ ) = escapeDBName name showAlterTable table (DropUniqueConstraint cname) = concat [ "ALTER TABLE " , escapeDBName table , " DROP INDEX " , escapeDBName cname ] -- | Render an action that must be done on a column. showAlter :: DBName -> AlterColumn' -> String showAlter table (n, Change col) = concat [ "ALTER TABLE " , escapeDBName table , " CHANGE " , escapeDBName n , showColumn col ] showAlter table (_, Add col) = concat [ "ALTER TABLE " , escapeDBName table , " ADD COLUMN " , showColumn col ] showAlter table (n, Drop) = concat [ "ALTER TABLE " , escapeDBName table , " DROP COLUMN " , escapeDBName n ] showAlter table (n, Default s) = concat [ "ALTER TABLE " , escapeDBName table , " ALTER COLUMN " , escapeDBName n , " SET DEFAULT " , s ] showAlter table (n, NoDefault) = concat [ "ALTER TABLE " , escapeDBName table , " ALTER COLUMN " , escapeDBName n , " DROP DEFAULT" ] showAlter table (n, Update s) = concat [ "UPDATE " , escapeDBName table , " SET " , escapeDBName n , "=" , s , " WHERE " , escapeDBName n , " IS NULL" ] showAlter table (n, AddReference t2 id2) = concat [ "ALTER TABLE " , escapeDBName table , " ADD CONSTRAINT " , escapeDBName $ refName table n , " FOREIGN KEY(" , escapeDBName n , ") REFERENCES " , escapeDBName t2 , "(" , escapeDBName id2 , ")" ] showAlter table (_, DropReference cname) = concat [ "ALTER TABLE " , escapeDBName table , " DROP CONSTRAINT " , escapeDBName cname ] refName :: DBName -> DBName -> DBName refName (DBName table) (DBName column) = DBName $ T.concat [table, "_", column, "_fkey"] ---------------------------------------------------------------------- -- | Escape a database name to be included on a query. -- -- FIXME: Can we do better here? escapeDBName :: DBName -> String escapeDBName (DBName s) = T.unpack s -- | Information required to connect to a MySQL database -- using @persistent@'s generic facilities. These values are the -- same that are given to 'withMySQLPool'. data MySQLConf = MySQLConf { myConnInfo :: MySQL.ConnectInfo -- ^ The connection information. , myPoolSize :: Int -- ^ How many connections should be held on the connection pool. } instance PersistConfig MySQLConf where type PersistConfigBackend MySQLConf = SqlPersist type PersistConfigPool MySQLConf = ConnectionPool createPoolConfig (MySQLConf cs size) = createMySQLPool cs size runPool _ = runSqlPool loadConfig (Object o) = do database <- o .: "database" host <- o .: "host" port <- o .: "port" user <- o .: "user" password <- o .: "password" pool <- o .: "poolsize" let ci = MySQL.defaultConnectInfo { MySQL.connectHost = host , MySQL.connectPort = port , MySQL.connectUser = user , MySQL.connectPassword = password , MySQL.connectDatabase = database } return $ MySQLConf ci pool loadConfig _ = mzero applyEnv conf = do env <- getEnvironment let maybeEnv old var = maybe old id $ lookup ("MYSQL_" ++ var) env return conf { myConnInfo = case myConnInfo conf of MySQL.ConnectInfo { MySQL.connectHost = host , MySQL.connectPort = port , MySQL.connectUser = user , MySQL.connectPassword = password , MySQL.connectDatabase = database } -> (myConnInfo conf) { MySQL.connectHost = maybeEnv host "HOST" , MySQL.connectPort = read $ maybeEnv (show port) "PORT" , MySQL.connectUser = maybeEnv user "USER" , MySQL.connectPassword = maybeEnv password "PASSWORD" , MySQL.connectDatabase = maybeEnv database "DATABASE" } }