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Restore the old code, giving a comparison with hasql-th

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Nikita Volkov 2020-06-07 11:40:52 +03:00
parent 809604683f
commit 736652c354
1 changed files with 29 additions and 6 deletions
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@ -57,10 +57,11 @@ import Prelude
import Data.Int
import Data.Functor.Contravariant
import Hasql.Session (Session)
import Hasql.Statement (Statement)
import Hasql.Statement (Statement(..))
import qualified Hasql.Session as Session
import qualified Hasql.Decoders as Decoders
import qualified Hasql.Encoders as Encoders
import qualified Hasql.Connection as Connection
import qualified Hasql.TH as TH -- from "hasql-th"
main :: IO ()
@ -98,12 +99,34 @@ sumAndDivModSession a b c = do
--
-- It's recommended to define statements in a dedicated 'Statements'
-- submodule of your project.
--
-- In the following code we use the extension library "hasql-th",
-- which generates statement definitions from SQL,
-- compile-time checking the syntax on the way.
-------------------------
sumStatement :: Statement (Int64, Int64) Int64
sumStatement = Statement sql encoder decoder True where
sql = "select $1 + $2"
encoder =
(fst >$< Encoders.param (Encoders.nonNullable Encoders.int8)) <>
(snd >$< Encoders.param (Encoders.nonNullable Encoders.int8))
decoder = Decoders.singleRow (Decoders.column (Decoders.nonNullable Decoders.int8))
divModStatement :: Statement (Int64, Int64) (Int64, Int64)
divModStatement = Statement sql encoder decoder True where
sql = "select $1 / $2, $1 % $2"
encoder =
(fst >$< Encoders.param (Encoders.nonNullable Encoders.int8)) <>
(snd >$< Encoders.param (Encoders.nonNullable Encoders.int8))
decoder = Decoders.singleRow row where
row =
(,) <$>
Decoders.column (Decoders.nonNullable Decoders.int8) <*>
Decoders.column (Decoders.nonNullable Decoders.int8)
```
For the general use-case it is advised to prefer declaring statements using the "hasql-th" library, which validates the statements at compile-time and generates codecs automatically. So the above two statements could be implemented the following way:
```haskell
import qualified Hasql.TH as TH -- from "hasql-th"
sumStatement :: Statement (Int64, Int64) Int64
sumStatement =
[TH.singletonStatement|