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FromRow.hs
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FromRow.hs
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{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE RecordWildCards, FlexibleInstances, DefaultSignatures #-}
------------------------------------------------------------------------------
-- |
-- Module: Database.PostgreSQL.Simple.FromRow
-- Copyright: (c) 2012 Leon P Smith
-- License: BSD3
-- Maintainer: Leon P Smith <leon@melding-monads.com>
-- Stability: experimental
--
-- The 'FromRow' typeclass, for converting a row of results
-- returned by a SQL query into a more useful Haskell representation.
--
-- Predefined instances are provided for tuples containing up to ten
-- elements. The instances for 'Maybe' types return 'Nothing' if all
-- the columns that would have been otherwise consumed are null, otherwise
-- it attempts a regular conversion.
--
------------------------------------------------------------------------------
module Database.PostgreSQL.Simple.FromRow
( FromRow(..)
, RowParser
, field
, fieldWith
, numFieldsRemaining
) where
import Prelude hiding (null)
import Control.Applicative (Applicative(..), (<$>), (<|>), (*>), liftA2)
import Control.Monad (replicateM, replicateM_)
import Control.Monad.Trans.State.Strict
import Control.Monad.Trans.Reader
import Control.Monad.Trans.Class
import Data.ByteString (ByteString)
import qualified Data.ByteString.Char8 as B
import Data.Vector (Vector)
import qualified Data.Vector as V
import Database.PostgreSQL.Simple.Types (Only(..))
import qualified Database.PostgreSQL.LibPQ as PQ
import Database.PostgreSQL.Simple.Internal
import Database.PostgreSQL.Simple.Compat
import Database.PostgreSQL.Simple.FromField
import Database.PostgreSQL.Simple.Ok
import Database.PostgreSQL.Simple.Types ((:.)(..), Null)
import Database.PostgreSQL.Simple.TypeInfo
import GHC.Generics
-- | A collection type that can be converted from a sequence of fields.
-- Instances are provided for tuples up to 10 elements and lists of any length.
--
-- Note that instances can be defined outside of postgresql-simple, which is
-- often useful. For example, here's an instance for a user-defined pair:
--
-- @
-- data User = User { name :: String, fileQuota :: Int }
--
-- instance 'FromRow' User where
-- fromRow = User \<$\> 'field' \<*\> 'field'
-- @
--
-- The number of calls to 'field' must match the number of fields returned
-- in a single row of the query result. Otherwise, a 'ConversionFailed'
-- exception will be thrown.
--
-- Note that 'field' evaluates its result to WHNF, so the caveats listed in
-- mysql-simple and very early versions of postgresql-simple no longer apply.
-- Instead, look at the caveats associated with user-defined implementations
-- of 'fromField'.
class FromRow a where
fromRow :: RowParser a
default fromRow :: (Generic a, GFromRow (Rep a)) => RowParser a
fromRow = to <$> gfromRow
getvalue :: PQ.Result -> PQ.Row -> PQ.Column -> Maybe ByteString
getvalue result row col = unsafeDupablePerformIO (PQ.getvalue' result row col)
nfields :: PQ.Result -> PQ.Column
nfields result = unsafeDupablePerformIO (PQ.nfields result)
getTypeInfoByCol :: Row -> PQ.Column -> Conversion TypeInfo
getTypeInfoByCol Row{..} col =
Conversion $ \conn -> do
oid <- PQ.ftype rowresult col
Ok <$> getTypeInfo conn oid
getTypenameByCol :: Row -> PQ.Column -> Conversion ByteString
getTypenameByCol row col = typname <$> getTypeInfoByCol row col
fieldWith :: FieldParser a -> RowParser a
fieldWith fieldP = RP $ do
let unCol (PQ.Col x) = fromIntegral x :: Int
r@Row{..} <- ask
column <- lift get
lift (put (column + 1))
let ncols = nfields rowresult
if (column >= ncols)
then lift $ lift $ do
vals <- mapM (getTypenameByCol r) [0..ncols-1]
let err = ConversionFailed
(show (unCol ncols) ++ " values: " ++ show (map ellipsis vals))
Nothing
""
("at least " ++ show (unCol column + 1)
++ " slots in target type")
"mismatch between number of columns to \
\convert and number in target type"
conversionError err
else do
let !result = rowresult
!typeOid = unsafeDupablePerformIO (PQ.ftype result column)
!field = Field{..}
lift (lift (fieldP field (getvalue result row column)))
field :: FromField a => RowParser a
field = fieldWith fromField
ellipsis :: ByteString -> ByteString
ellipsis bs
| B.length bs > 15 = B.take 10 bs `B.append` "[...]"
| otherwise = bs
numFieldsRemaining :: RowParser Int
numFieldsRemaining = RP $ do
Row{..} <- ask
column <- lift get
return $! (\(PQ.Col x) -> fromIntegral x) (nfields rowresult - column)
null :: RowParser Null
null = field
instance (FromField a) => FromRow (Only a) where
fromRow = Only <$> field
instance (FromField a) => FromRow (Maybe (Only a)) where
fromRow = (null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b) => FromRow (a,b) where
fromRow = (,) <$> field <*> field
instance (FromField a, FromField b) => FromRow (Maybe (a,b)) where
fromRow = (null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c) => FromRow (a,b,c) where
fromRow = (,,) <$> field <*> field <*> field
instance (FromField a, FromField b, FromField c) => FromRow (Maybe (a,b,c)) where
fromRow = (null *> null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d) =>
FromRow (a,b,c,d) where
fromRow = (,,,) <$> field <*> field <*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d) =>
FromRow (Maybe (a,b,c,d)) where
fromRow = (null *> null *> null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e) =>
FromRow (a,b,c,d,e) where
fromRow = (,,,,) <$> field <*> field <*> field <*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e) =>
FromRow (Maybe (a,b,c,d,e)) where
fromRow = (null *> null *> null *> null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f) =>
FromRow (a,b,c,d,e,f) where
fromRow = (,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f) =>
FromRow (Maybe (a,b,c,d,e,f)) where
fromRow = (null *> null *> null *> null *> null *>
null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g) =>
FromRow (a,b,c,d,e,f,g) where
fromRow = (,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g) =>
FromRow (Maybe (a,b,c,d,e,f,g)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h) =>
FromRow (a,b,c,d,e,f,g,h) where
fromRow = (,,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h) =>
FromRow (Maybe (a,b,c,d,e,f,g,h)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i) =>
FromRow (a,b,c,d,e,f,g,h,i) where
fromRow = (,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i) =>
FromRow (Maybe (a,b,c,d,e,f,g,h,i)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j) =>
FromRow (a,b,c,d,e,f,g,h,i,j) where
fromRow = (,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j) =>
FromRow (Maybe (a,b,c,d,e,f,g,h,i,j)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k) =>
FromRow (a,b,c,d,e,f,g,h,i,j,k) where
fromRow = (,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k) =>
FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l) =>
FromRow (a,b,c,d,e,f,g,h,i,j,k,l) where
fromRow = (,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l) =>
FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m) =>
FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m) where
fromRow = (,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m) =>
FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n) =>
FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n) where
fromRow = (,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n) =>
FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> null *> null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n, FromField o) =>
FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o) where
fromRow = (,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n, FromField o) =>
FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n, FromField o,
FromField p) =>
FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p) where
fromRow = (,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n, FromField o,
FromField p) =>
FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n, FromField o,
FromField p, FromField q) =>
FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q) where
fromRow = (,,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n, FromField o,
FromField p, FromField q) =>
FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n, FromField o,
FromField p, FromField q, FromField r) =>
FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r) where
fromRow = (,,,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n, FromField o,
FromField p, FromField q, FromField r) =>
FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n, FromField o,
FromField p, FromField q, FromField r, FromField s) =>
FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s) where
fromRow = (,,,,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n, FromField o,
FromField p, FromField q, FromField r, FromField s) =>
FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> null *> null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n, FromField o,
FromField p, FromField q, FromField r, FromField s, FromField t) =>
FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t) where
fromRow = (,,,,,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
<*> field <*> field <*> field <*> field <*> field
instance (FromField a, FromField b, FromField c, FromField d, FromField e,
FromField f, FromField g, FromField h, FromField i, FromField j,
FromField k, FromField l, FromField m, FromField n, FromField o,
FromField p, FromField q, FromField r, FromField s, FromField t) =>
FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t)) where
fromRow = (null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *>
null *> null *> null *> null *> null *> pure Nothing)
<|> (Just <$> fromRow)
instance FromField a => FromRow [a] where
fromRow = do
n <- numFieldsRemaining
replicateM n field
instance FromField a => FromRow (Maybe [a]) where
fromRow = do
n <- numFieldsRemaining
(replicateM_ n null *> pure Nothing) <|> (Just <$> replicateM n field)
instance FromField a => FromRow (Vector a) where
fromRow = do
n <- numFieldsRemaining
V.replicateM n field
instance FromField a => FromRow (Maybe (Vector a)) where
fromRow = do
n <- numFieldsRemaining
(replicateM_ n null *> pure Nothing) <|> (Just <$> V.replicateM n field)
instance (FromRow a, FromRow b) => FromRow (a :. b) where
fromRow = (:.) <$> fromRow <*> fromRow
-- Type class for default implementation of FromRow using generics
class GFromRow f where
gfromRow :: RowParser (f p)
instance GFromRow f => GFromRow (M1 c i f) where
gfromRow = M1 <$> gfromRow
instance (GFromRow f, GFromRow g) => GFromRow (f :*: g) where
gfromRow = liftA2 (:*:) gfromRow gfromRow
instance (FromField a) => GFromRow (K1 R a) where
gfromRow = K1 <$> field
instance GFromRow U1 where
gfromRow = pure U1