private boolean nextIterator() {
            while (++currentSummaryDataIndex < hit.summaries.size()) {
                currentIterator = iteratorFor(hit.summaries.get(currentSummaryDataIndex));
                if (currentIterator.hasNext())
                    return true;
            }
            return false;
        }
Advanced to the next non-empty iterator, if any
container-search/src/main/java/com/yahoo/prelude/fastsearch/FastHit.java