private Result retrieveHits() {
            Result result = execution.search(query);
            // ensure that field sddocname is available
            execution.fill(result); // TODO: Suffices to fill attributes
            if (initialResult != null) {
                initialResult.hits().addErrorsFrom(result.hits());
            }
            return result;
        }
Groups hits according to document type.
For each group, the desired number of hits can be specified.

@author Tony Vaagenes
container-search/src/main/java/com/yahoo/prelude/searcher/MultipleResultsSearcher.java