@@ -1,4 +1,6 @@
1−{-# LANGUAGE RecordWildCards #-}
1+{-# LANGUAGE FlexibleContexts #-}
2+{-# LANGUAGE RecordWildCards, FlexibleInstances, DefaultSignatures #-}
3------------------------------------------------------------------------------
5------------------------------------------------------------------------------
@@ -7,13 +9,15 @@
7-- License: BSD3
9-- License: BSD3
8-- Maintainer: Leon P Smith <leon@melding-monads.com>
10-- Maintainer: Leon P Smith <leon@melding-monads.com>
9-- Stability: experimental
11-- Stability: experimental
10−-- Portability: portable
12-- The 'FromRow' typeclass, for converting a row of results
13-- The 'FromRow' typeclass, for converting a row of results
13-- returned by a SQL query into a more useful Haskell representation.
14-- returned by a SQL query into a more useful Haskell representation.
15-- Predefined instances are provided for tuples containing up to ten
16-- Predefined instances are provided for tuples containing up to ten
16−-- elements.
17+-- elements. The instances for 'Maybe' types return 'Nothing' if all
18+-- the columns that would have been otherwise consumed are null, otherwise
19+-- it attempts a regular conversion.
17------------------------------------------------------------------------------
21------------------------------------------------------------------------------
19module Database.PostgreSQL.Simple.FromRow
23module Database.PostgreSQL.Simple.FromRow
@@ -24,31 +28,36 @@ module Database.PostgreSQL.Simple.FromRow
24 , numFieldsRemaining
28 , numFieldsRemaining
31+import Prelude hiding (null)
27−import Control.Applicative (Applicative(..), (<$>))
32+import Control.Applicative (Applicative(..), (<$>), (<|>), (*>), liftA2)
28−import Control.Exception (SomeException(..))
29−import Control.Monad (replicateM)
33+import Control.Monad (replicateM, replicateM_)
34+import Control.Monad.Trans.State.Strict
35+import Control.Monad.Trans.Reader
36+import Control.Monad.Trans.Class
30−import Data.ByteString (ByteString)
37+import Data.ByteString (ByteString)
31import qualified Data.ByteString.Char8 as B
38import qualified Data.ByteString.Char8 as B
39+import Data.Vector (Vector)
40+import qualified Data.Vector as V
32−import Database.PostgreSQL.Simple.Types (Only(..))
41+import Database.PostgreSQL.Simple.Types (Only(..))
33−import Database.PostgreSQL.Simple.Ok
34import qualified Database.PostgreSQL.LibPQ as PQ
42import qualified Database.PostgreSQL.LibPQ as PQ
35import Database.PostgreSQL.Simple.Internal
43import Database.PostgreSQL.Simple.Internal
44+import Database.PostgreSQL.Simple.Compat
36import Database.PostgreSQL.Simple.FromField
45import Database.PostgreSQL.Simple.FromField
37−import Database.PostgreSQL.Simple.Types ((:.)(..))
46+import Database.PostgreSQL.Simple.Ok
47+import Database.PostgreSQL.Simple.Types ((:.)(..), Null)
48+import Database.PostgreSQL.Simple.TypeInfo
39−import Control.Monad.Trans.State.Strict
50+import GHC.Generics
40−import Control.Monad.Trans.Reader
41−import Control.Monad.Trans.Class
43−import Data.Vector ((!))
45-- | A collection type that can be converted from a sequence of fields.
53-- | A collection type that can be converted from a sequence of fields.
46-- Instances are provided for tuples up to 10 elements and lists of any length.
54-- Instances are provided for tuples up to 10 elements and lists of any length.
48−-- Note that instances can defined outside of postgresql-simple, which is
56+-- Note that instances can be defined outside of postgresql-simple, which is
49-- often useful. For example, here's an instance for a user-defined pair:
57-- often useful. For example, here's an instance for a user-defined pair:
51−-- @data User = User { name :: String, fileQuota :: Int }
60+-- data User = User { name :: String, fileQuota :: Int }
53-- instance 'FromRow' User where
62-- instance 'FromRow' User where
54-- fromRow = User \<$\> 'field' \<*\> 'field'
63-- fromRow = User \<$\> 'field' \<*\> 'field'
@@ -58,12 +67,47 @@ import Data.Vector ((!))
58-- in a single row of the query result. Otherwise, a 'ConversionFailed'
67-- in a single row of the query result. Otherwise, a 'ConversionFailed'
59-- exception will be thrown.
68-- exception will be thrown.
70+-- You can also derive 'FromRow' for your data type using GHC generics, like
74+-- \{-# LANGUAGE DeriveAnyClass \#-}
75+-- \{-# LANGUAGE DeriveGeneric \#-}
77+-- import "GHC.Generics" ('GHC.Generics.Generic')
78+-- import "Database.PostgreSQL.Simple" ('FromRow')
80+-- data User = User { name :: String, fileQuota :: Int }
81+-- deriving ('GHC.Generics.Generic', 'FromRow')
84+-- Note that this only works for product types (e.g. records) and does not
85+-- support sum types or recursive types.
61−-- Note that 'field' evaluates it's result to WHNF, so the caveats listed in
87+-- Note that 'field' evaluates its result to WHNF, so the caveats listed in
62−-- previous versions of postgresql-simple no longer apply. Instead, look
88+-- mysql-simple and very early versions of postgresql-simple no longer apply.
63−-- at the caveats associated with user-defined implementations of 'fromRow'.
89+-- Instead, look at the caveats associated with user-defined implementations
65class FromRow a where
92class FromRow a where
66 fromRow :: RowParser a
93 fromRow :: RowParser a
94+ default fromRow :: (Generic a, GFromRow (Rep a)) => RowParser a
95+ fromRow = to <$> gfromRow
97+getvalue :: PQ.Result -> PQ.Row -> PQ.Column -> Maybe ByteString
98+getvalue result row col = unsafeDupablePerformIO (PQ.getvalue' result row col)
100+nfields :: PQ.Result -> PQ.Column
101+nfields result = unsafeDupablePerformIO (PQ.nfields result)
103+getTypeInfoByCol :: Row -> PQ.Column -> Conversion TypeInfo
104+getTypeInfoByCol Row{..} col =
105+ Conversion $ \conn -> do
106+ oid <- PQ.ftype rowresult col
107+ Ok <$> getTypeInfo conn oid
109+getTypenameByCol :: Row -> PQ.Column -> Conversion ByteString
110+getTypenameByCol row col = typname <$> getTypeInfoByCol row col
68fieldWith :: FieldParser a -> RowParser a
112fieldWith :: FieldParser a -> RowParser a
69fieldWith fieldP = RP $ do
113fieldWith fieldP = RP $ do
@@ -73,24 +117,22 @@ fieldWith fieldP = RP $ do
73 lift (put (column + 1))
117 lift (put (column + 1))
74 let ncols = nfields rowresult
118 let ncols = nfields rowresult
75 if (column >= ncols)
119 if (column >= ncols)
76− then do
120+ then lift $ lift $ do
77− let vals = map (\c -> ( typenames r ! (unCol c)
121+ vals <- mapM (getTypenameByCol r) [0..ncols-1]
78− , fmap ellipsis (getvalue rowresult row c) ))
80− convertError = ConversionFailed
122+ let err = ConversionFailed
81− (show (unCol ncols) ++ " values: " ++ show vals)
123+ (show (unCol ncols) ++ " values: " ++ show (map ellipsis vals))
84 ("at least " ++ show (unCol column + 1)
126 ("at least " ++ show (unCol column + 1)
85 ++ " slots in target type")
127 ++ " slots in target type")
86 "mismatch between number of columns to \
128 "mismatch between number of columns to \
87 \convert and number in target type"
129 \convert and number in target type"
88− lift (lift (Errors [SomeException convertError]))
130+ conversionError err
90− let typeinfo = typeinfos ! unCol column
91− result = rowresult
132+ let !result = rowresult
133+ !typeOid = unsafeDupablePerformIO (PQ.ftype result column)
92− field = Field{..}
134+ !field' = Field{..}
93− lift (lift (fieldP field (getvalue result row column)))
135+ lift (lift (fieldP field' (getvalue result row column)))
95field :: FromField a => RowParser a
137field :: FromField a => RowParser a
96field = fieldWith fromField
138field = fieldWith fromField
@@ -106,57 +148,340 @@ numFieldsRemaining = RP $ do
106 column <- lift get
148 column <- lift get
107 return $! (\(PQ.Col x) -> fromIntegral x) (nfields rowresult - column)
149 return $! (\(PQ.Col x) -> fromIntegral x) (nfields rowresult - column)
151+null :: RowParser Null
109instance (FromField a) => FromRow (Only a) where
154instance (FromField a) => FromRow (Only a) where
110 fromRow = Only <$> field
155 fromRow = Only <$> field
157+instance (FromField a) => FromRow (Maybe (Only a)) where
158+ fromRow = (null *> pure Nothing)
159+ <|> (Just <$> fromRow)
112instance (FromField a, FromField b) => FromRow (a,b) where
161instance (FromField a, FromField b) => FromRow (a,b) where
113 fromRow = (,) <$> field <*> field
162 fromRow = (,) <$> field <*> field
164+instance (FromField a, FromField b) => FromRow (Maybe (a,b)) where
165+ fromRow = (null *> null *> pure Nothing)
166+ <|> (Just <$> fromRow)
115instance (FromField a, FromField b, FromField c) => FromRow (a,b,c) where
168instance (FromField a, FromField b, FromField c) => FromRow (a,b,c) where
116 fromRow = (,,) <$> field <*> field <*> field
169 fromRow = (,,) <$> field <*> field <*> field
171+instance (FromField a, FromField b, FromField c) => FromRow (Maybe (a,b,c)) where
172+ fromRow = (null *> null *> null *> pure Nothing)
173+ <|> (Just <$> fromRow)
118instance (FromField a, FromField b, FromField c, FromField d) =>
175instance (FromField a, FromField b, FromField c, FromField d) =>
119 FromRow (a,b,c,d) where
176 FromRow (a,b,c,d) where
120 fromRow = (,,,) <$> field <*> field <*> field <*> field
177 fromRow = (,,,) <$> field <*> field <*> field <*> field
179+instance (FromField a, FromField b, FromField c, FromField d) =>
180+ FromRow (Maybe (a,b,c,d)) where
181+ fromRow = (null *> null *> null *> null *> pure Nothing)
182+ <|> (Just <$> fromRow)
122instance (FromField a, FromField b, FromField c, FromField d, FromField e) =>
184instance (FromField a, FromField b, FromField c, FromField d, FromField e) =>
123 FromRow (a,b,c,d,e) where
185 FromRow (a,b,c,d,e) where
124 fromRow = (,,,,) <$> field <*> field <*> field <*> field <*> field
186 fromRow = (,,,,) <$> field <*> field <*> field <*> field <*> field
188+instance (FromField a, FromField b, FromField c, FromField d, FromField e) =>
189+ FromRow (Maybe (a,b,c,d,e)) where
190+ fromRow = (null *> null *> null *> null *> null *> pure Nothing)
191+ <|> (Just <$> fromRow)
126instance (FromField a, FromField b, FromField c, FromField d, FromField e,
193instance (FromField a, FromField b, FromField c, FromField d, FromField e,
127 FromField f) =>
194 FromField f) =>
128 FromRow (a,b,c,d,e,f) where
195 FromRow (a,b,c,d,e,f) where
129 fromRow = (,,,,,) <$> field <*> field <*> field <*> field <*> field
196 fromRow = (,,,,,) <$> field <*> field <*> field <*> field <*> field
130 <*> field
197 <*> field
199+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
201+ FromRow (Maybe (a,b,c,d,e,f)) where
202+ fromRow = (null *> null *> null *> null *> null *>
203+ null *> pure Nothing)
204+ <|> (Just <$> fromRow)
132instance (FromField a, FromField b, FromField c, FromField d, FromField e,
206instance (FromField a, FromField b, FromField c, FromField d, FromField e,
133 FromField f, FromField g) =>
207 FromField f, FromField g) =>
134 FromRow (a,b,c,d,e,f,g) where
208 FromRow (a,b,c,d,e,f,g) where
135 fromRow = (,,,,,,) <$> field <*> field <*> field <*> field <*> field
209 fromRow = (,,,,,,) <$> field <*> field <*> field <*> field <*> field
136 <*> field <*> field
210 <*> field <*> field
212+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
213+ FromField f, FromField g) =>
214+ FromRow (Maybe (a,b,c,d,e,f,g)) where
215+ fromRow = (null *> null *> null *> null *> null *>
216+ null *> null *> pure Nothing)
217+ <|> (Just <$> fromRow)
138instance (FromField a, FromField b, FromField c, FromField d, FromField e,
219instance (FromField a, FromField b, FromField c, FromField d, FromField e,
139 FromField f, FromField g, FromField h) =>
220 FromField f, FromField g, FromField h) =>
140 FromRow (a,b,c,d,e,f,g,h) where
221 FromRow (a,b,c,d,e,f,g,h) where
141 fromRow = (,,,,,,,) <$> field <*> field <*> field <*> field <*> field
222 fromRow = (,,,,,,,) <$> field <*> field <*> field <*> field <*> field
142 <*> field <*> field <*> field
223 <*> field <*> field <*> field
225+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
226+ FromField f, FromField g, FromField h) =>
227+ FromRow (Maybe (a,b,c,d,e,f,g,h)) where
228+ fromRow = (null *> null *> null *> null *> null *>
229+ null *> null *> null *> pure Nothing)
230+ <|> (Just <$> fromRow)
144instance (FromField a, FromField b, FromField c, FromField d, FromField e,
232instance (FromField a, FromField b, FromField c, FromField d, FromField e,
145 FromField f, FromField g, FromField h, FromField i) =>
233 FromField f, FromField g, FromField h, FromField i) =>
146 FromRow (a,b,c,d,e,f,g,h,i) where
234 FromRow (a,b,c,d,e,f,g,h,i) where
147 fromRow = (,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
235 fromRow = (,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
148 <*> field <*> field <*> field <*> field
236 <*> field <*> field <*> field <*> field
238+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
239+ FromField f, FromField g, FromField h, FromField i) =>
240+ FromRow (Maybe (a,b,c,d,e,f,g,h,i)) where
241+ fromRow = (null *> null *> null *> null *> null *>
242+ null *> null *> null *> null *> pure Nothing)
243+ <|> (Just <$> fromRow)
150instance (FromField a, FromField b, FromField c, FromField d, FromField e,
245instance (FromField a, FromField b, FromField c, FromField d, FromField e,
151 FromField f, FromField g, FromField h, FromField i, FromField j) =>
246 FromField f, FromField g, FromField h, FromField i, FromField j) =>
152 FromRow (a,b,c,d,e,f,g,h,i,j) where
247 FromRow (a,b,c,d,e,f,g,h,i,j) where
153 fromRow = (,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
248 fromRow = (,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
154 <*> field <*> field <*> field <*> field <*> field
249 <*> field <*> field <*> field <*> field <*> field
251+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
252+ FromField f, FromField g, FromField h, FromField i, FromField j) =>
253+ FromRow (Maybe (a,b,c,d,e,f,g,h,i,j)) where
254+ fromRow = (null *> null *> null *> null *> null *>
255+ null *> null *> null *> null *> null *> pure Nothing)
256+ <|> (Just <$> fromRow)
258+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
259+ FromField f, FromField g, FromField h, FromField i, FromField j,
261+ FromRow (a,b,c,d,e,f,g,h,i,j,k) where
262+ fromRow = (,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
263+ <*> field <*> field <*> field <*> field <*> field
266+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
267+ FromField f, FromField g, FromField h, FromField i, FromField j,
269+ FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k)) where
270+ fromRow = (null *> null *> null *> null *> null *>
271+ null *> null *> null *> null *> null *>
272+ null *> pure Nothing)
273+ <|> (Just <$> fromRow)
275+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
276+ FromField f, FromField g, FromField h, FromField i, FromField j,
277+ FromField k, FromField l) =>
278+ FromRow (a,b,c,d,e,f,g,h,i,j,k,l) where
279+ fromRow = (,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
280+ <*> field <*> field <*> field <*> field <*> field
283+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
284+ FromField f, FromField g, FromField h, FromField i, FromField j,
285+ FromField k, FromField l) =>
286+ FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l)) where
287+ fromRow = (null *> null *> null *> null *> null *>
288+ null *> null *> null *> null *> null *>
289+ null *> null *> pure Nothing)
290+ <|> (Just <$> fromRow)
292+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
293+ FromField f, FromField g, FromField h, FromField i, FromField j,
294+ FromField k, FromField l, FromField m) =>
295+ FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m) where
296+ fromRow = (,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
297+ <*> field <*> field <*> field <*> field <*> field
298+ <*> field <*> field <*> field
300+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
301+ FromField f, FromField g, FromField h, FromField i, FromField j,
302+ FromField k, FromField l, FromField m) =>
303+ FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m)) where
304+ fromRow = (null *> null *> null *> null *> null *>
305+ null *> null *> null *> null *> null *>
306+ null *> null *> null *> pure Nothing)
307+ <|> (Just <$> fromRow)
309+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
310+ FromField f, FromField g, FromField h, FromField i, FromField j,
311+ FromField k, FromField l, FromField m, FromField n) =>
312+ FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n) where
313+ fromRow = (,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
314+ <*> field <*> field <*> field <*> field <*> field
315+ <*> field <*> field <*> field <*> field
317+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
318+ FromField f, FromField g, FromField h, FromField i, FromField j,
319+ FromField k, FromField l, FromField m, FromField n) =>
320+ FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n)) where
321+ fromRow = (null *> null *> null *> null *> null *>
322+ null *> null *> null *> null *> null *>
323+ null *> null *> null *> null *> pure Nothing)
324+ <|> (Just <$> fromRow)
326+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
327+ FromField f, FromField g, FromField h, FromField i, FromField j,
328+ FromField k, FromField l, FromField m, FromField n, FromField o) =>
329+ FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o) where
330+ fromRow = (,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
331+ <*> field <*> field <*> field <*> field <*> field
332+ <*> field <*> field <*> field <*> field <*> field
334+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
335+ FromField f, FromField g, FromField h, FromField i, FromField j,
336+ FromField k, FromField l, FromField m, FromField n, FromField o) =>
337+ FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o)) where
338+ fromRow = (null *> null *> null *> null *> null *>
339+ null *> null *> null *> null *> null *>
340+ null *> null *> null *> null *> null *> pure Nothing)
341+ <|> (Just <$> fromRow)
343+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
344+ FromField f, FromField g, FromField h, FromField i, FromField j,
345+ FromField k, FromField l, FromField m, FromField n, FromField o,
347+ FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p) where
348+ fromRow = (,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
349+ <*> field <*> field <*> field <*> field <*> field
350+ <*> field <*> field <*> field <*> field <*> field
353+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
354+ FromField f, FromField g, FromField h, FromField i, FromField j,
355+ FromField k, FromField l, FromField m, FromField n, FromField o,
357+ FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p)) where
358+ fromRow = (null *> null *> null *> null *> null *>
359+ null *> null *> null *> null *> null *>
360+ null *> null *> null *> null *> null *>
361+ null *> pure Nothing)
362+ <|> (Just <$> fromRow)
364+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
365+ FromField f, FromField g, FromField h, FromField i, FromField j,
366+ FromField k, FromField l, FromField m, FromField n, FromField o,
367+ FromField p, FromField q) =>
368+ FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q) where
369+ fromRow = (,,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
370+ <*> field <*> field <*> field <*> field <*> field
371+ <*> field <*> field <*> field <*> field <*> field
374+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
375+ FromField f, FromField g, FromField h, FromField i, FromField j,
376+ FromField k, FromField l, FromField m, FromField n, FromField o,
377+ FromField p, FromField q) =>
378+ FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q)) where
379+ fromRow = (null *> null *> null *> null *> null *>
380+ null *> null *> null *> null *> null *>
381+ null *> null *> null *> null *> null *>
382+ null *> null *> pure Nothing)
383+ <|> (Just <$> fromRow)
385+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
386+ FromField f, FromField g, FromField h, FromField i, FromField j,
387+ FromField k, FromField l, FromField m, FromField n, FromField o,
388+ FromField p, FromField q, FromField r) =>
389+ FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r) where
390+ fromRow = (,,,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
391+ <*> field <*> field <*> field <*> field <*> field
392+ <*> field <*> field <*> field <*> field <*> field
393+ <*> field <*> field <*> field
395+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
396+ FromField f, FromField g, FromField h, FromField i, FromField j,
397+ FromField k, FromField l, FromField m, FromField n, FromField o,
398+ FromField p, FromField q, FromField r) =>
399+ FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r)) where
400+ fromRow = (null *> null *> null *> null *> null *>
401+ null *> null *> null *> null *> null *>
402+ null *> null *> null *> null *> null *>
403+ null *> null *> null *> pure Nothing)
404+ <|> (Just <$> fromRow)
406+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
407+ FromField f, FromField g, FromField h, FromField i, FromField j,
408+ FromField k, FromField l, FromField m, FromField n, FromField o,
409+ FromField p, FromField q, FromField r, FromField s) =>
410+ FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s) where
411+ fromRow = (,,,,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
412+ <*> field <*> field <*> field <*> field <*> field
413+ <*> field <*> field <*> field <*> field <*> field
414+ <*> field <*> field <*> field <*> field
416+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
417+ FromField f, FromField g, FromField h, FromField i, FromField j,
418+ FromField k, FromField l, FromField m, FromField n, FromField o,
419+ FromField p, FromField q, FromField r, FromField s) =>
420+ FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s)) where
421+ fromRow = (null *> null *> null *> null *> null *>
422+ null *> null *> null *> null *> null *>
423+ null *> null *> null *> null *> null *>
424+ null *> null *> null *> null *> pure Nothing)
425+ <|> (Just <$> fromRow)
427+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
428+ FromField f, FromField g, FromField h, FromField i, FromField j,
429+ FromField k, FromField l, FromField m, FromField n, FromField o,
430+ FromField p, FromField q, FromField r, FromField s, FromField t) =>
431+ FromRow (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t) where
432+ fromRow = (,,,,,,,,,,,,,,,,,,,) <$> field <*> field <*> field <*> field <*> field
433+ <*> field <*> field <*> field <*> field <*> field
434+ <*> field <*> field <*> field <*> field <*> field
435+ <*> field <*> field <*> field <*> field <*> field
437+instance (FromField a, FromField b, FromField c, FromField d, FromField e,
438+ FromField f, FromField g, FromField h, FromField i, FromField j,
439+ FromField k, FromField l, FromField m, FromField n, FromField o,
440+ FromField p, FromField q, FromField r, FromField s, FromField t) =>
441+ FromRow (Maybe (a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t)) where
442+ fromRow = (null *> null *> null *> null *> null *>
443+ null *> null *> null *> null *> null *>
444+ null *> null *> null *> null *> null *>
445+ null *> null *> null *> null *> null *> pure Nothing)
446+ <|> (Just <$> fromRow)
156instance FromField a => FromRow [a] where
448instance FromField a => FromRow [a] where
157 fromRow = do
449 fromRow = do
158 n <- numFieldsRemaining
450 n <- numFieldsRemaining
159 replicateM n field
451 replicateM n field
453+instance FromField a => FromRow (Maybe [a]) where
455+ n <- numFieldsRemaining
456+ (replicateM_ n null *> pure Nothing) <|> (Just <$> replicateM n field)
458+instance FromField a => FromRow (Vector a) where
460+ n <- numFieldsRemaining
461+ V.replicateM n field
463+instance FromField a => FromRow (Maybe (Vector a)) where
465+ n <- numFieldsRemaining
466+ (replicateM_ n null *> pure Nothing) <|> (Just <$> V.replicateM n field)
161instance (FromRow a, FromRow b) => FromRow (a :. b) where
468instance (FromRow a, FromRow b) => FromRow (a :. b) where
162 fromRow = (:.) <$> fromRow <*> fromRow
469 fromRow = (:.) <$> fromRow <*> fromRow
473+-- Type class for default implementation of FromRow using generics
474+class GFromRow f where
475+ gfromRow :: RowParser (f p)
477+instance GFromRow f => GFromRow (M1 c i f) where
478+ gfromRow = M1 <$> gfromRow
480+instance (GFromRow f, GFromRow g) => GFromRow (f :*: g) where
481+ gfromRow = liftA2 (:*:) gfromRow gfromRow
483+instance (FromField a) => GFromRow (K1 R a) where
484+ gfromRow = K1 <$> field
486+instance GFromRow U1 where