class HashIndex extends AbstractMapBasedAttributeIndex<A, O, ConcurrentMap<A, StoredResultSet<O>>> implements KeyStatisticsAttributeIndex<A, O>, OnHeapTypeIndex {

    @Override
    public Integer getCountOfDistinctKeys(QueryOptions queryOptions) {
        return super.getCountOfDistinctKeys(queryOptions);
    }

    protected  HashIndex(Factory<ConcurrentMap<A, StoredResultSet<O>>> indexMapFactory, Factory<StoredResultSet<O>> valueSetFactory, Attribute<O, A> attribute);

}