@@ -40,6 +40,8 @@ type DbConn = (C.SessionId, C.Connection)
40newtype Db a = Db {runDb :: ReaderT DbConn IO a}
40newtype Db a = Db {runDb :: ReaderT DbConn IO a}
41 deriving (Functor, Applicative, Monad, MonadIO)
41 deriving (Functor, Applicative, Monad, MonadIO)
43+-- This exception type should never be observable by the API users.
44+-- It merely carries errors which end up as RelError at the end of a transaction.
43newtype TransactionCancelled = TransactionCancelled DbError deriving Show
45newtype TransactionCancelled = TransactionCancelled DbError deriving Show
44instance Exception TransactionCancelled
46instance Exception TransactionCancelled