'Get persisted data for this buffer from the db.
Raises NotFoundInDatabase is not there.'

def _load_buf_data_once(self, skip_once_check=False):

    if (skip_once_check or (not self._have_checked_db)):
        self._have_checked_db = True
        (self._scan_time_cache, self._scan_error_cache, self._blob_from_lang_cache) = self.mgr.db.get_buf_data(self)
