public function insert($key,
        $columns,
        $timestamp=null,
        $ttl=null,
        $consistency_level=null) {

        if ($timestamp === null)
            $timestamp = Clock::get_time();

        $cfmap = array();
        $packed_key = $this->pack_key($key);
        $cfmap[$packed_key][$this->column_family] =
            $this->make_mutation($columns, $timestamp, $ttl);

        return $this->pool->call("batch_mutate", $cfmap, $this->wcl($consistency_level));
    }