src/Rel8/Expr/Serialize.hs · rel8

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rel8/src/Rel8/Expr/Serialize.hs

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1{-# language FlexibleContexts #-}

2{-# language NamedFieldPuns #-}

3{-# language TypeFamilies #-}

5module Rel8.Expr.Serialize

6 ( litExpr

7 , slitExpr

8 , sparseValue

9 )

10where

12-- base

13import Prelude

15-- hasql

16import qualified Hasql.Decoders as Hasql

18-- opaleye

19import qualified Opaleye.Internal.HaskellDB.PrimQuery as Opaleye

21-- rel8

22import {-# SOURCE #-} Rel8.Expr ( Expr( Expr ) )

23import Rel8.Expr.Opaleye ( scastExpr )

24import Rel8.Schema.Null ( Unnullify, Nullity( Null, NotNull ), Sql, nullable )

25import Rel8.Type ( DBType, typeInformation )

26import Rel8.Type.Information ( TypeInformation(..) )

29-- | Produce an expression from a literal.

31-- Note that you can usually use 'Rel8.lit', but @litExpr@ can solve problems

32-- of inference in polymorphic code.

33litExpr :: Sql DBType a => a -> Expr a

34litExpr = slitExpr nullable typeInformation

37slitExpr :: Nullity a -> TypeInformation (Unnullify a) -> a -> Expr a

38slitExpr nullity info@TypeInformation {encode} =

39 scastExpr info . Expr . encoder

40 where

41 encoder = case nullity of

42 Null -> maybe (Opaleye.ConstExpr Opaleye.NullLit) encode

43 NotNull -> encode

46sparseValue :: Nullity a -> TypeInformation (Unnullify a) -> Hasql.Row a

47sparseValue nullity TypeInformation {decode} = case nullity of

48 Null -> Hasql.column $ Hasql.nullable decode

49 NotNull -> Hasql.column $ Hasql.nonNullable decode