Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

260 lines (220 sloc) 9.951 kb
{-# LANGUAGE CPP, DeriveDataTypeable, DeriveFunctor, FlexibleInstances #-}
{-# LANGUAGE PatternGuards, ScopedTypeVariables, OverloadedStrings #-}
------------------------------------------------------------------------------
-- |
-- Module: Database.PostgreSQL.Simple.QueryResults
-- Copyright: (c) 2011 MailRank, Inc.
-- (c) 2011 Leon P Smith
-- License: BSD3
-- Maintainer: Leon P Smith <leon@melding-monads.com>
-- Stability: experimental
-- Portability: portable
--
-- The 'Result' typeclass, for converting a single value in a row
-- returned by a SQL query into a more useful Haskell representation.
--
-- A Haskell numeric type is considered to be compatible with all
-- PostgreSQL numeric types that are less accurate than it. For instance,
-- the Haskell 'Double' type is compatible with the PostgreSQL's 32-bit
-- @Int@ type because it can represent a @Int@ exactly. On the other hand,
-- since a 'Double' might lose precision if representing a 64-bit @BigInt@,
-- the two are /not/ considered compatible.
--
------------------------------------------------------------------------------
module Database.PostgreSQL.Simple.Result
(
Result(..)
, ResultError(..)
) where
#include "MachDeps.h"
import Control.Applicative (Applicative, (<$>), (<*>), (<*), pure)
import Control.Exception (SomeException(..), Exception, throw)
import Data.Attoparsec.Char8 hiding (Result)
import Data.Bits ((.&.), (.|.), shiftL)
import Data.ByteString (ByteString)
import qualified Data.ByteString.Char8 as B
import Data.Int (Int16, Int32, Int64)
import Data.List (foldl')
import Data.Ratio (Ratio)
import Data.Time.Calendar (Day, fromGregorian)
import Data.Time.Clock (UTCTime)
import Data.Time.Format (parseTime)
import Data.Time.LocalTime (TimeOfDay, makeTimeOfDayValid)
import Data.Typeable (TypeRep, Typeable, typeOf)
import Data.Word (Word64)
import Database.PostgreSQL.Simple.Internal
import Database.PostgreSQL.Simple.Field (Field(..), RawResult(..))
import Database.PostgreSQL.Simple.BuiltinTypes
import Database.PostgreSQL.Simple.Types (Binary(..))
import qualified Database.PostgreSQL.LibPQ as PQ
import System.IO.Unsafe (unsafePerformIO)
import System.Locale (defaultTimeLocale)
import qualified Data.ByteString as SB
import qualified Data.ByteString.Char8 as B8
import qualified Data.ByteString.Lazy as LB
import qualified Data.Text as ST
import qualified Data.Text.Encoding as ST
import qualified Data.Text.Encoding.Error (UnicodeException)
import qualified Data.Text.Lazy as LT
-- | Exception thrown if conversion from a SQL value to a Haskell
-- value fails.
data ResultError = Incompatible { errSQLType :: String
, errHaskellType :: String
, errMessage :: String }
-- ^ The SQL and Haskell types are not compatible.
| UnexpectedNull { errSQLType :: String
, errHaskellType :: String
, errMessage :: String }
-- ^ A SQL @NULL@ was encountered when the Haskell
-- type did not permit it.
| ConversionFailed { errSQLType :: String
, errHaskellType :: String
, errMessage :: String }
-- ^ The SQL value could not be parsed, or could not
-- be represented as a valid Haskell value, or an
-- unexpected low-level error occurred (e.g. mismatch
-- between metadata and actual data in a row).
deriving (Eq, Show, Typeable)
instance Exception ResultError
left :: Exception a => a -> Either SomeException b
left = Left . SomeException
-- | A type that may be converted from a SQL type.
class Result a where
convert :: Field -> Maybe ByteString -> Either SomeException a
-- ^ Convert a SQL value to a Haskell value.
--
-- Returns an exception if the conversion fails. In the case of
-- library instances, this will usually be a 'ResultError', but may
-- be a 'UnicodeException'.
instance (Result a) => Result (Maybe a) where
convert _ Nothing = pure Nothing
convert f bs = Just <$> convert f bs
instance Result Bool where
convert f bs
| typeOid f /= builtin2oid Bool = returnError Incompatible f ""
| bs == Nothing = returnError UnexpectedNull f ""
| bs == Just "t" = pure True
| bs == Just "f" = pure False
| otherwise = returnError ConversionFailed f ""
instance Result Int16 where
convert = atto ok16 $ signed decimal
instance Result Int32 where
convert = atto ok32 $ signed decimal
instance Result Int where
convert = atto okInt $ signed decimal
instance Result Int64 where
convert = atto ok64 $ signed decimal
instance Result Integer where
convert = atto ok64 $ signed decimal
instance Result Float where
convert = atto ok (realToFrac <$> double)
where ok = mkCompats [Float4,Int2]
instance Result Double where
convert = atto ok double
where ok = mkCompats [Float4,Float8,Int2,Int4]
instance Result (Ratio Integer) where
convert = atto ok rational
where ok = mkCompats [Float4,Float8,Int2,Int4,Numeric]
unBinary (Binary x) = x
instance Result SB.ByteString where
convert f dat = if typeOid f == builtin2oid Bytea
then unBinary <$> convert f dat
else doConvert f okText' pure dat
instance Result PQ.Oid where
convert f dat = PQ.Oid <$> atto (mkCompat Oid) decimal f dat
instance Result LB.ByteString where
convert f dat = LB.fromChunks . (:[]) <$> convert f dat
unescapeBytea :: Field -> SB.ByteString
-> Either SomeException (Binary SB.ByteString)
unescapeBytea f str = case unsafePerformIO (PQ.unescapeBytea str) of
Nothing -> returnError ConversionFailed f "unescapeBytea failed"
Just str -> pure (Binary str)
instance Result (Binary SB.ByteString) where
convert f dat = case format f of
PQ.Text -> doConvert f okBinary (unescapeBytea f) dat
PQ.Binary -> doConvert f okBinary (pure . Binary) dat
instance Result (Binary LB.ByteString) where
convert f dat = Binary . LB.fromChunks . (:[]) . unBinary <$> convert f dat
instance Result ST.Text where
convert f = doConvert f okText $ (either left Right . ST.decodeUtf8')
{- | isText f = doConvert f okText $ (Right . ST.decodeUtf8)
| otherwise = incompatible f (typeOf ST.empty)
"attempt to mix binary and text" -}
-- FIXME: check character encoding
instance Result LT.Text where
convert f dat = LT.fromStrict <$> convert f dat
instance Result [Char] where
convert f dat = ST.unpack <$> convert f dat
instance Result UTCTime where
convert f = doConvert f ok $ \bs ->
case parseTime defaultTimeLocale "%F %T%Q%z" (B8.unpack bs ++ "00") of
Just t -> Right t
Nothing -> returnError ConversionFailed f "could not parse"
where ok = mkCompats [TimestampWithTimeZone]
{--
instance Result Day where
convert f = flip (atto ok) f $ case fieldType f of
Year -> year
_ -> date
where ok = mkCompats [Year,Date,NewDate]
year = fromGregorian <$> decimal <*> pure 1 <*> pure 1
date = fromGregorian <$> (decimal <* char '-')
<*> (decimal <* char '-')
<*> decimal
instance Result TimeOfDay where
convert f = flip (atto ok) f $ do
hours <- decimal <* char ':'
mins <- decimal <* char ':'
secs <- decimal :: Parser Int
case makeTimeOfDayValid hours mins (fromIntegral secs) of
Just t -> return t
_ -> conversionFailed f "TimeOfDay" "could not parse"
where ok = mkCompats [Time]
isText :: Field -> Bool
isText f = fieldCharSet f /= 63
--}
newtype Compat = Compat Word64
mkCompats :: [BuiltinType] -> Compat
mkCompats = foldl' f (Compat 0) . map mkCompat
where f (Compat a) (Compat b) = Compat (a .|. b)
mkCompat :: BuiltinType -> Compat
mkCompat = Compat . shiftL 1 . fromEnum
compat :: Compat -> Compat -> Bool
compat (Compat a) (Compat b) = a .&. b /= 0
okText, okText', ok16, ok32, ok64 :: Compat
okText = mkCompats [Name,Text,Char,Bpchar,Varchar]
okText' = mkCompats [Name,Text,Char,Bpchar,Varchar,Unknown]
okBinary = mkCompats [Bytea]
ok16 = mkCompats [Int2]
ok32 = mkCompats [Int2,Int4]
ok64 = mkCompats [Int2,Int4,Int8]
#if WORD_SIZE_IN_BITS < 64
okInt = ok32
#else
okInt = ok64
#endif
doConvert :: forall a . (Typeable a)
=> Field -> Compat -> (ByteString -> Either SomeException a)
-> Maybe ByteString -> Either SomeException a
doConvert f types cvt (Just bs)
| Just typ <- oid2builtin (typeOid f)
, mkCompat typ `compat` types = cvt bs
| otherwise = returnError Incompatible f "types incompatible"
doConvert f _ _ _ = returnError UnexpectedNull f ""
returnError :: forall a err . (Typeable a, Exception err)
=> (String -> String -> String -> err)
-> Field -> String -> Either SomeException a
returnError mkErr f = left . mkErr (B.unpack (typename f))
(show (typeOf (undefined :: a)))
atto :: forall a. (Typeable a)
=> Compat -> Parser a -> Field -> Maybe ByteString
-> Either SomeException a
atto types p0 f dat = doConvert f types (go p0) dat
where
go :: Parser a -> ByteString -> Either SomeException a
go p s =
case parseOnly p s of
Left err -> returnError ConversionFailed f err
Right v -> Right v
instance Result RawResult where
convert field rawData = Right (RawResult field rawData)
Jump to Line
Something went wrong with that request. Please try again.