protected function searchSelect(SearchableSubquery $subquery, ColumnCollection $columns, array $words)
    {
        $cases = $bindings = [];

        foreach ($columns as $column) {
            list($cases[], $binding) = $this->buildCase($column, $words);

            $bindings = array_merge_recursive($bindings, $binding);
        }

        $select = implode(' + ', $cases);

        $subquery->selectRaw("max({$select}) as relevance");

        $this->addBinding($bindings['select'], 'select');

        return $bindings['where'];
    }