public List<FacetResult> accumulate(List<MatchingDocs> matchingDocs) throws IOException {
FacetsAggregator aggregator = getAggregator();
for (CategoryListParams clp : getCategoryLists()) {
for (MatchingDocs md : matchingDocs) {
aggregator.aggregate(md, clp, facetArrays);
}
}
// compute top-K
List<FacetResult> results = new ArrayList<FacetResult>();