DocSet to BitSet

[Kevin Osborn]

I have a custom query object that extends ContstantScoreQuery. I give it a key 
which pulls some documents out of a cache. Thinking to make it more efficient, 
I used DocSet, backed by OpenBitSet or OpenHashSet. However, I need to set the 
BitSet object for the Lucene filter. Any idea on how to best do this from 
DocSet? It seems like this is a problem that people have encountered before.

I could iterate through each item in the DocSet and do that, but that seems 
rather inefficient.

public class MyQuery extends ConstantScoreQuery {   
    private static class ResellerSupplierFilter extends Filter {
        private final BitSet bitset;
        
        public MyFilter(String reseller, String supplier) {           
            DocSet docset = 
(DocSet)context.get().searcher.getCache("my-filter").get(new 
CompositeKey(reseller, supplier));
        }

        public @Override BitSet bits(IndexReader reader) {
            //return docset.getBits().
        }

        public @Override int hashCode() {
            return new 
HashCodeBuilder().append(reseller).append(supplier).toHashCode();
        }
    }
    
    public ResellerSupplierQuery(String reseller, String supplier) {
        super(new ResellerSupplierFilter(reseller, supplier));
    }
}