| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
MessageDb.Projection
Description
A projection is an aggregation of all messages in a stream.
Synopsis
- data Projection state = Projection {
- initial :: state
- handlers :: ProjectionHandlers state
- data BatchSize
- data UnprocessedMessage = UnprocessedMessage {
- message :: Message
- reason :: HandleError
- data Projected state = Projected {
- unprocessed :: [UnprocessedMessage]
- state :: state
- version :: StreamVersion
- versionIncludingUnprocessed :: Projected state -> StreamVersion
- project :: Projection state -> NonEmpty Message -> Projected state
- fetch :: forall state. WithConnection -> BatchSize -> StreamName -> Projection state -> IO (Maybe (Projected state))
Documentation
data Projection state Source #
Defines how to perform a projection a stream.
Constructors
| Projection | |
Fields
| |
Constructors
| FixedSize NumberOfMessages | |
| Unlimited |
data UnprocessedMessage Source #
A message that was not able to be processed.
Constructors
| UnprocessedMessage | |
Fields
| |
Instances
| Eq UnprocessedMessage Source # | |
Defined in MessageDb.Projection Methods (==) :: UnprocessedMessage -> UnprocessedMessage -> Bool # (/=) :: UnprocessedMessage -> UnprocessedMessage -> Bool # | |
| Show UnprocessedMessage Source # | |
Defined in MessageDb.Projection Methods showsPrec :: Int -> UnprocessedMessage -> ShowS # show :: UnprocessedMessage -> String # showList :: [UnprocessedMessage] -> ShowS # | |
| Exception UnprocessedMessage Source # | |
Defined in MessageDb.Projection Methods toException :: UnprocessedMessage -> SomeException # fromException :: SomeException -> Maybe UnprocessedMessage # | |
A projected state
Constructors
| Projected | |
Fields
| |
versionIncludingUnprocessed :: Projected state -> StreamVersion Source #
Version of the projection with unprocessed messages included.
project :: Projection state -> NonEmpty Message -> Projected state Source #
Project a state of a stream by aggregating messages.
fetch :: forall state. WithConnection -> BatchSize -> StreamName -> Projection state -> IO (Maybe (Projected state)) Source #
Query a stream and project the messages.