Database.Muesli.Backend.Types

Generic backend interface types and classes.

This module is re-exported by other modules, like Database.Muesli.Handle.

Transaction log records

data TransRecord

This type represents a line in the transaction log file. There can be multiple lines for a single transaction, and the last one must be a Completed one. Other than that, the lines from multiple transactions can be mixed.

Constructors

Pending LogRecord

Completed TransactionId

Instances

Show TransRecord

data LogRecord

Holds the metadata for a given document version.

Keys collected by the generic scrapper are stored in recReferences, recSortables, and recUniques. The recDocumentKey is generated by an IdSupply, while the recAddress and recSize are allocated by alloc. This work is done either by the primitive queries in Database.Muesli.Query, or by runQuery.

Constructors

LogRecord

Fields

recTransactionId :: !TransactionId

recDocumentKey :: !DocumentKey

recReferences :: ![(PropertyKey, DocumentKey)]

recSortables :: ![(PropertyKey, SortableKey)]

recUniques :: ![(PropertyKey, UniqueKey)]

recAddress :: !DocAddress

recSize :: !DocSize

recDeleted :: !Bool

Instances

Show LogRecord

Generic backend interface

These classes are used by the machinary in Database.Muesli.State.

For an implementation, see the Database.Muesli.Backend.File module.

class (Show a, DbHandle (LogHandleOf a), DataHandle (DataHandleOf a)) => LogState a where

Provides stateful access to an abstract log file handle.

Associated Types

type LogHandleOf a :: *

type DataHandleOf a :: *

Methods

logHandle :: a -> LogHandleOf a

logInit :: MonadIO m => LogHandleOf a -> m a

logAppend :: MonadIO m => a -> [TransRecord] -> m a

logRead :: MonadIO m => a -> m (Maybe TransRecord)

Instances

LogState FileLogState

class DbHandle a => DataHandle a where

Handle used to access serialized document data in the generic data file.

Methods

readDocument :: MonadIO m => a -> LogRecord -> m ByteString

writeDocument :: MonadIO m => LogRecord -> ByteString -> a -> m ()

Instances

DataHandle FileHandle

type DbPath = String

Generic path type. For instance, this can be a file path or an url.

class DbHandle a where

Generic handle interface.

Methods

openDb :: MonadIO m => DbPath -> m a

closeDb :: MonadIO m => a -> m ()

withDb :: MonadIO m => DbPath -> (a -> IO b) -> m b

swapDb :: MonadIO m => DbPath -> DbPath -> m a

Instances

DbHandle FileHandle