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.Nullability

25 ( Unnullify

26 , Nullability( Nullable, NonNullable )

27 , Sql, nullabilization

28 )

29import Rel8.Type ( DBType, typeInformation )

30import Rel8.Type.Information ( TypeInformation(..) )

33-- | Produce an expression from a literal.

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

36-- of inference in polymorphic code.

37litExpr :: Sql DBType a => a -> Expr a

38litExpr = slitExpr nullabilization typeInformation

41slitExpr :: Nullability a -> TypeInformation (Unnullify a) -> a -> Expr a

42slitExpr nullability info@TypeInformation {encode} =

43 scastExpr info . Expr . encoder

44 where

45 encoder = case nullability of

46 Nullable -> maybe (Opaleye.ConstExpr Opaleye.NullLit) encode

47 NonNullable -> encode

50sparseValue :: Nullability a -> TypeInformation (Unnullify a) -> Hasql.Row a

51sparseValue nullability TypeInformation {decode} = case nullability of

52 Nullable -> Hasql.column $ Hasql.nullable decode

53 NonNullable -> Hasql.column $ Hasql.nonNullable decode