@Override
    public String getIndexedString() {
        StringBuilder buf = new StringBuilder();

        for (Iterator<Item> i = getItemIterator(); i.hasNext();) {
            IndexedItem indexedItem = (IndexedItem) i.next();

            buf.append(indexedItem.getIndexedString());
            if (i.hasNext()) {
                buf.append(' ');
            }
        }
        return buf.toString();
    }
Segment phrase items uses a empty heading instead of "SPHRASE "
container-search/src/main/java/com/yahoo/prelude/query/PhraseSegmentItem.java