new RandomScoreFunctionBuilder().seed(sessionId.hashCode())) }),
                    0, pollingFetchSize, SortBuilders.scoreSort().order(SortOrder.DESC));
        } else if (!ORDER_SEQUENTIAL.equals(crawlOrder)) {
            logger.warn("Invalid crawl order specified: {}. Falling back to sequential.", crawlOrder);
        }

    protected SortBuilder<?> createFieldSortBuilder(final String field, final SortOrder order) {
        if (QueryFieldConfig.SCORE_FIELD.equals(field) || QueryFieldConfig.DOC_SCORE_FIELD.equals(field)) {
            return SortBuilders.scoreSort().order(order);
        }
        return SortBuilders.fieldSort(field).order(order);
    }

    /**
     * Checks if the specified field is a search field.
     * @param field The field name to check.