// Take newer values from item2
        mergedItem.setTimestamp(item2.getTimestamp());
        mergedItem.setUserBoost(item2.getUserBoost());
        mergedItem.setEmptySource(item2.toEmptyMap());

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

        return mergedItem;
    }

        this.id = id;
    }

    /**
     * Returns an empty map with default values for suggest item fields.
     * @return An empty map.
     */
    public Map<String, Object> toEmptyMap() {
        return emptySource;
    }

    /**
     * Creates an empty map with default values for suggest item fields.
     * @return An empty map.
     */