private function getM2MDbTable($meta)
    {
        if (null !== $this->relation->through) {
            return $this->relation->through->getMeta()->getDbTable();
        } elseif ($this->dbTable) {
            return $this->dbTable;
        } else {
            // oracle allows identifier of 30 chars max
            return StringHelper::truncate(
                sprintf('%s_%s', $meta->getDbTable(), $this->getName()),
                30, null, null,
                $meta->getRegistry()->getOrm()->getCharset()
            );
        }
    }