@Override
    protected void doPartialFill(Result result, String summaryClass) {
        if (result.isFilled(summaryClass)) return;

        Query query = result.getQuery();
        traceQuery(getName(), DispatchPhase.FILL, query, query.getOffset(), query.getHits(), 1, quotedSummaryClass(query, summaryClass));

        try (FillInvoker invoker = getFillInvoker(result)) {
            invoker.fill(result, summaryClass);
        }
    }
Perform a partial docsum fill for a temporary result
representing a partition of the complete fill request.

@param result result containing a partition of the unfilled hits
@param summaryClass the summary class we want to fill with
container-search/src/main/java/com/yahoo/prelude/fastsearch/IndexedBackend.java