MessageDb.Projection

A projection is an aggregation of all messages in a stream.

Documentation

data Projection state

Defines how to perform a projection a stream.

Constructors

Projection

Fields

• initial :: state
• handlers :: ProjectionHandlers state

data UnprocessedMessage

A message that was not able to be processed.

Constructors

UnprocessedMessage

Fields

• message :: Message
• reason :: HandleError

Instances

Eq UnprocessedMessage

Defined in MessageDb.Projection

Methods

(==) :: UnprocessedMessage -> UnprocessedMessage -> Bool

(/=) :: UnprocessedMessage -> UnprocessedMessage -> Bool

Show UnprocessedMessage

Defined in MessageDb.Projection

Methods

showsPrec :: Int -> UnprocessedMessage -> ShowS

show :: UnprocessedMessage -> String

showList :: [UnprocessedMessage] -> ShowS

Exception UnprocessedMessage

Defined in MessageDb.Projection

Methods

toException :: UnprocessedMessage -> SomeException

fromException :: SomeException -> Maybe UnprocessedMessage

displayException :: UnprocessedMessage -> String

data Projected state

A projected state

Constructors

Projected

Fields

• unprocessed :: [UnprocessedMessage]
• state :: state
• version :: StreamVersion

Instances

Functor Projected

Defined in MessageDb.Projection

Methods

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

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

Eq state => Eq (Projected state)

Defined in MessageDb.Projection

Methods

(==) :: Projected state -> Projected state -> Bool

(/=) :: Projected state -> Projected state -> Bool

Show state => Show (Projected state)

Defined in MessageDb.Projection

Methods

showsPrec :: Int -> Projected state -> ShowS

show :: Projected state -> String

showList :: [Projected state] -> ShowS

versionIncludingUnprocessed :: Projected state -> StreamVersion

Version of the projection with unprocessed messages included.

project :: Projection state -> NonEmpty Message -> Projected state

Project a state of a stream by aggregating messages.

fetch :: forall state. WithConnection -> BatchSize -> StreamName -> Projection state -> IO (Maybe (Projected state))

Query a stream and project the messages.

newtype SnapshotStreamName

Constructors

SnapshotStreamName

Fields

• fromSnapshotStreamName :: StreamName

Instances

Eq SnapshotStreamName

Defined in MessageDb.Projection

Methods

(==) :: SnapshotStreamName -> SnapshotStreamName -> Bool

(/=) :: SnapshotStreamName -> SnapshotStreamName -> Bool

Ord SnapshotStreamName

Defined in MessageDb.Projection

Methods

compare :: SnapshotStreamName -> SnapshotStreamName -> Ordering

(<) :: SnapshotStreamName -> SnapshotStreamName -> Bool

(<=) :: SnapshotStreamName -> SnapshotStreamName -> Bool

(>) :: SnapshotStreamName -> SnapshotStreamName -> Bool

(>=) :: SnapshotStreamName -> SnapshotStreamName -> Bool

max :: SnapshotStreamName -> SnapshotStreamName -> SnapshotStreamName

min :: SnapshotStreamName -> SnapshotStreamName -> SnapshotStreamName

Show SnapshotStreamName

Defined in MessageDb.Projection

Methods

showsPrec :: Int -> SnapshotStreamName -> ShowS

show :: SnapshotStreamName -> String

showList :: [SnapshotStreamName] -> ShowS

IsString SnapshotStreamName

Defined in MessageDb.Projection

Methods

fromString :: String -> SnapshotStreamName

Semigroup SnapshotStreamName

Defined in MessageDb.Projection

Methods

(<>) :: SnapshotStreamName -> SnapshotStreamName -> SnapshotStreamName

sconcat :: NonEmpty SnapshotStreamName -> SnapshotStreamName

stimes :: Integral b => b -> SnapshotStreamName -> SnapshotStreamName

fetchWithSnapshots :: forall state. (ToJSON state, FromJSON state) => WithConnection -> BatchSize -> StreamName -> Projection state -> SnapshotStreamName -> IO (Maybe (Projected state))