src/Rel8/Query/Values.hs · rel8

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rel8/src/Rel8/Query/Values.hs

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1{-# language FlexibleContexts #-}

3module Rel8.Query.Values

4 ( values

5 )

6where

8-- base

9import Data.Foldable ( toList )

10import Prelude

12-- opaleye

13import qualified Opaleye.Values as Opaleye

15-- rel8

16import {-# SOURCE #-} Rel8.Query ( Query )

17import Rel8.Query.Opaleye ( fromOpaleye )

18import Rel8.Table ( Table )

19import Rel8.Table.Opaleye ( valuesspec )

20import Rel8.Schema.Context ( DB )

23-- | Construct a query that returns the given input list of rows. This is like

24-- folding a list of 'return' statements under 'union', but uses the SQL

25-- @VALUES@ expression for efficiency.

27-- Typically @values@ will be used with 'lit':

29-- >>> mapM_ Data.Text.IO.putStrLn =<< select c (values [ lit "Hello", lit "World!" ])

30-- Hello

31-- World!

32values :: (Table DB a, Foldable f) => f a -> Query a

33values = fromOpaleye . Opaleye.valuesExplicit valuesspec . toList