Database.DuckDB.Connection

Error reporting

type DuckDBError = String

isDuckDBError :: DuckDBState -> Bool

Monad

newtype DuckDBMonad a

Constructors

DuckDBMonad

Fields

• runDuckDBMonad :: ExceptT DuckDBError IO a

Instances

MonadIO DuckDBMonad

Defined in Database.DuckDB.Internal

Methods

liftIO :: IO a -> DuckDBMonad a

Applicative DuckDBMonad

Defined in Database.DuckDB.Internal

Methods

pure :: a -> DuckDBMonad a

(<*>) :: DuckDBMonad (a -> b) -> DuckDBMonad a -> DuckDBMonad b

liftA2 :: (a -> b -> c) -> DuckDBMonad a -> DuckDBMonad b -> DuckDBMonad c

(*>) :: DuckDBMonad a -> DuckDBMonad b -> DuckDBMonad b

(<*) :: DuckDBMonad a -> DuckDBMonad b -> DuckDBMonad a

Functor DuckDBMonad

Defined in Database.DuckDB.Internal

Methods

fmap :: (a -> b) -> DuckDBMonad a -> DuckDBMonad b

(<$) :: a -> DuckDBMonad b -> DuckDBMonad a

Monad DuckDBMonad

Defined in Database.DuckDB.Internal

Methods

(>>=) :: DuckDBMonad a -> (a -> DuckDBMonad b) -> DuckDBMonad b

(>>) :: DuckDBMonad a -> DuckDBMonad b -> DuckDBMonad b

return :: a -> DuckDBMonad a

MonadError DuckDBError DuckDBMonad

Defined in Database.DuckDB.Internal

Methods

throwError :: DuckDBError -> DuckDBMonad a

catchError :: DuckDBMonad a -> (DuckDBError -> DuckDBMonad a) -> DuckDBMonad a

liftIO :: MonadIO m => IO a -> m a

Lift a computation from the IO monad. This allows us to run IO computations in any monadic stack, so long as it supports these kinds of operations (i.e. IO is the base monad for the stack).

Example

import Control.Monad.Trans.State -- from the "transformers" library

printState :: Show s => StateT s IO ()
printState = do
  state <- get
  liftIO $ print state

Had we omitted liftIO, we would have ended up with this error:

• Couldn't match type ‘IO’ with ‘StateT s IO’
 Expected type: StateT s IO ()
   Actual type: IO ()

The important part here is the mismatch between StateT s IO () and IO ().

Luckily, we know of a function that takes an IO a and returns an (m a): liftIO, enabling us to run the program and see the expected results:

> evalStateT printState "hello"
"hello"

> evalStateT printState 3
3

liftIOEither :: IO (Either DuckDBError a) -> DuckDBMonad a

runDuckDB :: DuckDBMonad a -> IO (Either DuckDBError a)

Version

version :: DuckDBMonad String

Database and Connection

open :: String -> DuckDBMonad DuckDBDatabase

configure :: DuckDBMonad DuckDBConfig

configCount :: DuckDBMonad Int

getConfigFlag :: Int -> DuckDBMonad (String, String)

setConfig

Arguments

:: DuckDBConfig

-> String

name

-> String

option

-> DuckDBMonad ()

destroyConfig :: DuckDBConfig -> DuckDBMonad ()

openExt :: String -> DuckDBConfig -> DuckDBMonad DuckDBDatabase

connect :: DuckDBDatabase -> DuckDBMonad DuckDBConnection

defaultConnection :: DuckDBMonad (DuckDBDatabase, DuckDBConnection)

withDefaultConnection :: ((DuckDBDatabase, DuckDBConnection) -> DuckDBMonad a) -> DuckDBMonad a

close :: (DuckDBDatabase, DuckDBConnection) -> DuckDBMonad ()

closeConnection :: DuckDBConnection -> DuckDBMonad ()

closeDatabase :: DuckDBDatabase -> DuckDBMonad ()