mergedItem.setEmptySource(item2.toEmptyMap());

        // Sum frequencies
        mergedItem.setQueryFreq(item1.getQueryFreq() + item2.getQueryFreq());
        mergedItem.setDocFreq(item1.getDocFreq() + item2.getDocFreq());

        return mergedItem;
    }

    /**
     * Merges readings at a specific index from two reading arrays.
     */

        if (logger.isInfoEnabled()) {
            logger.info("Deleting document words: index={}", index);
        }
        return deleteWordsByKind(index, FieldNames.DOC_FREQ, SuggestItem.Kind.DOCUMENT, item -> item.setDocFreq(0), SuggestItem.Kind.QUERY,
                SuggestItem.Kind.USER);
    }

    /**
     * Deletes query words (words with QUERY_FREQ >= 1 that don't have DOCUMENT or USER kinds).
     *