public function getQueryFields()
    {
        // Not necessary to specify this unless boosting
        if (empty($this->boostedFields)) {
            return null;
        }
        $queryFields = array();
        foreach ($this->boostedFields as $fieldName => $boost) {
            $queryFields[] = $fieldName . '^' . $boost;
        }

        // If any fields are queried, we must always include the default field, otherwise it will be excluded
        $df = $this->getDefaultField();
        if ($queryFields && !isset($this->boostedFields[$df])) {
            $queryFields[] = $df;
        }

        return $queryFields;
    }