Servant.DB.PostgreSQL

Quick start

Automatic derive of typed DB API based on postgresql-query package.

How to use:

• Define your instances of MonadLogger and HasPostgres for your app monad: newtype PostgresM a = PostgresM { runPostgresM :: PgMonadT (LoggingT IO) a } deriving (Functor, HasPostgres, MonadLogger, Monad, Applicative, MonadBase IO)
• Define type level API: @ type UserId = Int

data RegisterUser = RegisterUser { userRegName :: String , userRegPassword :: String , userRegRegTime :: Day } deriving (Eq)

deriveToRow ''RegisterUser

data User = User { userId :: UserId , userName :: String , userPassword :: String , userRegTime :: Day } deriving (Eq)

deriveFromRow ''User deriveToRow ''User

type UserAPI = ArgNamed "u" (Composite RegisterUser) :> Procedure "postUser" (Only Int) :| ArgPos Int :> Procedure "getUser" (Maybe User) :| ArgPos Int :> Procedure "deleteUser" () :| Procedure "getUsers" [User] @

• Derive client functions from the API:

postUser :: Composite RegisterUser -> PostgresM (Only Int)
getUser :: Int -> PostgresM (Maybe User)
deleteUser :: Int -> PostgresM ()
getUsers :: PostgresM [User]
(      postUser
  :| getUser
  :| deleteUser
  :| getUsers) = deriveDB (Proxy :: Proxy UserAPI) (Proxy :: Proxy PostgresM)

Features

• Call functions in schema with :> operator: type API = "test" :> ArgPos Int :> Procedure "square" (Only Int) That will call function `test.square(int)`.
• Composite types are defined with `Composite a` wrapper: type API = ArgNamed "u" (Composite UserCreate) :> Procedure "postUser" (Only Int)
• Support for arrays: type API = ArgPos (PGArray Int) :> Procedure "mleast" (Maybe (Only Int))
• Support for variadic arguments: type API = ArgPos (Variadic Int) :> Procedure "mleast" (Maybe (Only Int))
• Support for default arguments with Default wrapper: type API = ArgPos (Default Int) :> Procedure "foo" (Only Int)