public function createGraph(NamedNode $graph, array $options = [])
    {
        if (false === isset($this->getGraphs()[$graph->getUri()])) {
            // table names
            $g2t = $this->configuration['table-prefix'].'_g2t';
            $id2val = $this->configuration['table-prefix'].'_id2val';

            /*
             * for id2val table
             */
            $query = 'INSERT INTO '.$id2val.' (val) VALUES("'.$graph->getUri().'")';
            $this->store->queryDB($query, $this->store->getDBCon());
            $usedId = $this->store->getDBCon()->insert_id;

            /*
             * for g2t table
             */
            $newIdg2t = 1 + $this->getRowCount($g2t);
            $query = 'INSERT INTO '.$g2t.' (t, g) VALUES('.$newIdg2t.', '.$usedId.')';
            $this->store->queryDB($query, $this->store->getDBCon());
            $usedId = $this->store->getDBCon()->insert_id;
        }
    }