Safe Haskell	None
Language	Haskell2010

Database.PostgreSQL.Tx.Internal

Contents

Disclaimer
- Internals

Synopsis

data TxErrorType
- = TxSerializationFailure
- | TxDeadlockDetected
- | TxOtherError (Maybe String)
data TxException = TxException {
- errorType :: TxErrorType
- cause :: SomeException
}
type family TxEnvs (xs :: [*]) r :: Constraint where ...
class TxEnv a r where
- lookupTxEnv :: r -> a
newtype TxM r a = UnsafeTxM {
- unsafeUnTxM :: ReaderT r IO a
}
unsafeRunIOInTxM :: IO a -> TxM r a
unsafeMkTxM :: (r -> IO a) -> TxM r a
unsafeMksTxM :: TxEnv a r => (a -> IO b) -> TxM r b
unsafeRunTxM :: r -> TxM r a -> IO a
unsafeWithRunInIOTxM :: ((forall a. TxM r a -> IO a) -> IO b) -> TxM r b
askTxEnv :: TxEnv a r => TxM r a
unsafeLookupTxEnvIO :: TxEnv a r => r -> IO a
throwExceptionTx :: Exception e => e -> TxM r a
mapExceptionTx :: (Exception e, Exception e') => (e -> Maybe e') -> TxM r a -> TxM r a
shouldRetryTx :: TxException -> Bool
fromSqlState :: Maybe String -> TxErrorType
unsafeMkTxException :: Exception e => (e -> Maybe String) -> e -> TxException
unsafeMkTxException' :: Exception e => (e -> TxErrorType) -> e -> TxException

Disclaimer

Changes to this module will not be reflected in the library's version updates.

Internals

data TxErrorType Source #

Constructors

TxSerializationFailure
TxDeadlockDetected
TxOtherError (Maybe String)	PostgreSQL `errcode`, if applicable.

Instances

Instances details

Eq TxErrorType Source #
Instance details Defined in Database.PostgreSQL.Tx.Internal Methods (==) :: TxErrorType -> TxErrorType -> Bool # (/=) :: TxErrorType -> TxErrorType -> Bool #
Show TxErrorType Source #
Instance details Defined in Database.PostgreSQL.Tx.Internal Methods showsPrec :: Int -> TxErrorType -> ShowS # show :: TxErrorType -> String # showList :: [TxErrorType] -> ShowS #

data TxException Source #

Constructors

TxException
Fields errorType :: TxErrorType cause :: SomeException

Instances

Instances details

Show TxException Source #
Instance details Defined in Database.PostgreSQL.Tx.Internal Methods showsPrec :: Int -> TxException -> ShowS # show :: TxException -> String # showList :: [TxException] -> ShowS #
Exception TxException Source #
Instance details Defined in Database.PostgreSQL.Tx.Internal Methods toException :: TxException -> SomeException # fromException :: SomeException -> Maybe TxException # displayException :: TxException -> String #

type family TxEnvs (xs :: [*]) r :: Constraint where ... Source #

Type family which allows for specifying several TxEnv constraints as a type-level list.

Since: 0.2.0.0

Equations

TxEnvs '[] r = ()
TxEnvs (x ': xs) r = (TxEnv x r, TxEnvs xs r)

class TxEnv a r where Source #

A type class for specifying how to acquire an environment value to be used for running an implementation of a database library. For example, your database library will likely require some sort of connection value to discharge its effects; in this case, you'd want to define an instance of TxEnv MyDBEnv Connection and use TxM MyDBEnv as your monad for executing transactions.

Note that implementations should take care and ensure that multiple instances are compatible with one another. For example, let's say you have instances for both TxEnv E PgSimple.Connection and TxEnv E LibPQ.Connection; if both of these implementations are grabbing connections from a pool, you will end up with each of those database libraries using different connections, and thus, would be running in separate transactions!

Since: 0.2.0.0

Methods

lookupTxEnv :: r -> a Source #

Acquire a value a via the reader environment r which assists in running a TxM in a transaction.

Since: 0.2.0.0

Instances

Instances details

Select a xs => TxEnv a (HEnv xs) Source #

TxEnv instance for HEnv; selects the first a in the HEnv and makes it available via the runtime environment.

Since: 0.2.0.0

Instance details

Defined in Database.PostgreSQL.Tx.HEnv

Methods

lookupTxEnv :: HEnv xs -> a Source #

newtype TxM r a Source #

The transaction monad. Unifies all database integrations, regardless of library, into a single monad. The r type parameter represents the reader environment needed for applicable database libraries. For example, postgresql-simple needs a Connection to run its functions, so its interface will require that we can obtain a Connection from the r using the TxEnv type class.

Since: 0.2.0.0

Constructors

UnsafeTxM
Fields unsafeUnTxM :: ReaderT r IO a Convert a `TxM` action to raw `ReaderT` over `IO`. This is provided only to give adaptor libraries access to the underlying `IO` that `TxM` wraps. Since: 0.2.0.0

Instances

Instances details

Monad (TxM r) Source #
Instance details Defined in Database.PostgreSQL.Tx.Internal Methods (>>=) :: TxM r a -> (a -> TxM r b) -> TxM r b # (>>) :: TxM r a -> TxM r b -> TxM r b # return :: a -> TxM r a #
Functor (TxM r) Source #
Instance details Defined in Database.PostgreSQL.Tx.Internal Methods fmap :: (a -> b) -> TxM r a -> TxM r b # (<$) :: a -> TxM r b -> TxM r a #
MonadFail (TxM r) Source #
Instance details Defined in Database.PostgreSQL.Tx.Internal Methods fail :: String -> TxM r a #
Applicative (TxM r) Source #
Instance details Defined in Database.PostgreSQL.Tx.Internal Methods pure :: a -> TxM r a # (<>) :: TxM r (a -> b) -> TxM r a -> TxM r b # liftA2 :: (a -> b -> c) -> TxM r a -> TxM r b -> TxM r c # (>) :: TxM r a -> TxM r b -> TxM r b # (<*) :: TxM r a -> TxM r b -> TxM r a #
(TypeError ('Text "MonadIO is banned in TxM; use 'unsafeRunIOInTxM' if you are sure this is safe IO") :: Constraint) => MonadIO (TxM r) Source #	The `TxM` monad discourages performing arbitrary `IO` within a transaction, so this instance generates a type error when client code tries to call `liftIO`. Since: 0.1.0.0
Instance details Defined in Database.PostgreSQL.Tx.Internal Methods liftIO :: IO a -> TxM r a #
Semigroup a => Semigroup (TxM r a) Source #
Instance details Defined in Database.PostgreSQL.Tx.Internal Methods (<>) :: TxM r a -> TxM r a -> TxM r a # sconcat :: NonEmpty (TxM r a) -> TxM r a # stimes :: Integral b => b -> TxM r a -> TxM r a #
Monoid a => Monoid (TxM r a) Source #
Instance details Defined in Database.PostgreSQL.Tx.Internal Methods mempty :: TxM r a # mappend :: TxM r a -> TxM r a -> TxM r a # mconcat :: [TxM r a] -> TxM r a #

unsafeRunIOInTxM :: IO a -> TxM r a Source #

Run an IO action in TxM. Use this function with care - arbitrary IO should only be run within a transaction when truly necessary.

Since: 0.2.0.0

unsafeMkTxM :: (r -> IO a) -> TxM r a Source #

Construct a TxM using a reader function. Use this function with care - arbitrary IO should only be run within a transaction when truly necessary.

Since: 0.2.0.0

unsafeMksTxM :: TxEnv a r => (a -> IO b) -> TxM r b Source #

Similar to unsafeMkTxM but allows for constructing a TxM with a reader function using a specific value from the environment. Use this function with care - arbitrary IO should only be run within a transaction when truly necessary.

Since: 0.2.0.0

unsafeRunTxM :: r -> TxM r a -> IO a Source #

Run a TxM to IO given the database runtime environment r. Use of this function outside of test suites should be rare.

Since: 0.2.0.0

unsafeWithRunInIOTxM :: ((forall a. TxM r a -> IO a) -> IO b) -> TxM r b Source #

Run a TxM action in IO via the provided runner function. Use this function with care - arbitrary IO should only be run within a transaction when truly necessary.

Since: 0.2.0.0

askTxEnv :: TxEnv a r => TxM r a Source #

unsafeLookupTxEnvIO :: TxEnv a r => r -> IO a Source #

Analogous to lookupTxEnv but can be run in IO instead of TxM.

Since: 0.2.0.0

throwExceptionTx :: Exception e => e -> TxM r a Source #

Throw an exception.

Since: 0.2.0.0

mapExceptionTx :: (Exception e, Exception e') => (e -> Maybe e') -> TxM r a -> TxM r a Source #

Catch an exception and map it to another exception type before rethrowing.

Since: 0.2.0.0

shouldRetryTx :: TxException -> Bool Source #

fromSqlState :: Maybe String -> TxErrorType Source #

unsafeMkTxException :: Exception e => (e -> Maybe String) -> e -> TxException Source #

unsafeMkTxException' :: Exception e => (e -> TxErrorType) -> e -> TxException Source #