in migrator/src/main/scala/org/apache/pekko/persistence/jdbc/migrator/JournalMigrator.scala [82:88]
def migrate(): Future[Done] = Source
.fromPublisher(journalDB.stream(query))
.via(serializer.deserializeFlow)
.map {
case Success((repr, tags, ordering)) => (repr, tags, ordering)
case Failure(exception) => throw exception // blow-up on failure
}