Data.Acid.Advanced

Home of the more specialized functions.

Documentation

scheduleUpdate :: UpdateEvent event => AcidState (EventState event) -> event -> IO (MVar (EventResult event))

Issue an Update event and return immediately. The event is not durable before the MVar has been filled but the order of events is honored. The behavior in case of exceptions is exactly the same as for update.

If EventA is scheduled before EventB, EventA will be executed before EventB:

do scheduleUpdate acid EventA
   scheduleUpdate acid EventB
   

groupUpdates :: UpdateEvent event => AcidState (EventState event) -> [event] -> IO ()

Schedule multiple Update events and wait for them to be durable, but throw away their results. This is useful for importing existing datasets into an AcidState.

update' :: (UpdateEvent event, MonadIO m) => AcidState (EventState event) -> event -> m (EventResult event)

Same as update but lifted into any monad capable of doing IO.

query' :: (QueryEvent event, MonadIO m) => AcidState (EventState event) -> event -> m (EventResult event)

Same as query but lifted into any monad capable of doing IO.

class (Typeable ev, SafeCopy ev, Typeable (MethodResult ev), SafeCopy (MethodResult ev)) => Method ev where

The basic Method class. Each Method has an indexed result type and a unique tag.

Minimal complete definition

Nothing

Associated Types

type MethodResult ev

type MethodState ev

Methods

methodTag :: ev -> Tag

class SafeCopy st => IsAcidic st where

Methods

acidEvents

Arguments

:: [Event st]

List of events capable of updating or querying the state.

data Event st where

We distinguish between events that modify the state and those that do not.

UpdateEvents are executed in a MonadState context and have to be serialized to disk before they are considered durable.

QueryEvents are executed in a MonadReader context and obviously do not have to be serialized to disk.

Constructors

UpdateEvent :: UpdateEvent ev => (ev -> Update (EventState ev) (EventResult ev)) -> Event (EventState ev)

QueryEvent :: QueryEvent ev => (ev -> Query (EventState ev) (EventResult ev)) -> Event (EventState ev)