def getByInstanceId(self, instanceId, justPresent = True):
        cu = self.db.cursor()

        if justPresent:
            cu.execute("SELECT path, stream FROM DBTroveFiles "
                       "WHERE instanceId=? and isPresent=1", instanceId)
        else:
            cu.execute("SELECT path, stream FROM DBTroveFiles "
                       "WHERE instanceId=?", instanceId)

        for path, stream in cu:
            yield (path, stream)