void Build() {
            std::vector<utils::slice> key_slices;

            for (size_t i = 0; i < keys_.size(); i++) {
                key_slices.push_back(slice(keys_[i]));
            }

            filter_.clear();
            policy_->create_filter(&key_slices[0], key_slices.size(), &filter_);
            keys_.clear();

            if (kVerbose >= 2) DumpFilter();
        }