diff --git a/src/cpp/include/list_scanning.h b/src/cpp/include/list_scanning.h
index 2907581e..61cce709 100644
--- a/src/cpp/include/list_scanning.h
+++ b/src/cpp/include/list_scanning.h
@@ -285,7 +285,7 @@ inline void scan_list_with_ids_l2(const float *query_vec,
                                         int list_size,
                                         int d,
                                         TopkBuffer &buffer,
-                                        vector<bool> bitmap) {
+                                       const vector<bool> &bitmap) {
     const float *vec = list_vecs;
 
     if (bitmap.size() == 0) {
@@ -311,7 +311,7 @@ inline void scan_list(const float *query_vec,
                             int d,
                             TopkBuffer &buffer,
                             faiss::MetricType metric = faiss::METRIC_L2,
-                            vector<bool> bitmap = {}) {
+                            const vector<bool> &bitmap = {}) {
     // Dispatch based on metric type and whether list_ids is provided.
     if (metric == faiss::METRIC_INNER_PRODUCT) {
         if (list_ids == nullptr)
diff --git a/src/cpp/src/query_coordinator.cpp b/src/cpp/src/query_coordinator.cpp
index 227d8193..da9a86d7 100644
--- a/src/cpp/src/query_coordinator.cpp
+++ b/src/cpp/src/query_coordinator.cpp
@@ -476,9 +476,9 @@ shared_ptr<SearchResult> QueryCoordinator::worker_scan(
 std::vector<bool> create_bitmap(const std::shared_ptr<arrow::Table> attributes_table,
                                     int64_t *list_ids,
                                     int64_t list_size,
-                                    string filter_name,
-                                    string filter_column,
-                                    arrow::Datum filter_value) {
+                                    const string &filter_name,
+                                    const string &filter_column,
+                                    const arrow::Datum &filter_value) {
     
     std::vector<bool> bitmap(list_size, false);
     std::shared_ptr<arrow::ChunkedArray> filter_attribute_column = attributes_table->GetColumnByName(filter_column);
@@ -513,9 +513,9 @@ std::vector<bool> create_bitmap(const std::shared_ptr<arrow::Table> attributes_t
 void filter_out_vectors(const std::shared_ptr<arrow::Table> attributes_table,
                         TopkBuffer &topk_buf,
                         int buffer_size,
-                        string filter_name,
-                        string filter_column,
-                        arrow::Datum filter_value) {
+                        string &filter_name,
+                        string &filter_column,
+                        arrow::Datum &filter_value) {
 
     auto scanned_vectors = topk_buf.topk_;
     std::shared_ptr<arrow::ChunkedArray> filter_attribute_column = attributes_table->GetColumnByName(filter_column);
@@ -625,20 +625,6 @@ shared_ptr<SearchResult> QueryCoordinator::serial_scan(Tensor x, Tensor partitio
             std::shared_ptr<arrow::Table> partition_attributes_table = 
                             partition_manager_->partition_store_->partitions_[pi]->attributes_table_;
             int64_t list_size = partition_manager_->partition_store_->list_size(pi);
-
-            std::shared_ptr<arrow::Int64Array> id_array = nullptr;
-            std::shared_ptr<arrow::DoubleArray> price_array = nullptr;
-
-            std::unordered_map<int64_t, int64_t> id_to_price;
-
-            if (partition_attributes_table != nullptr) {
-                id_array = std::static_pointer_cast<arrow::Int64Array>(partition_attributes_table->GetColumnByName("id")->chunk(0));
-                price_array = std::static_pointer_cast<arrow::DoubleArray>(partition_attributes_table->GetColumnByName("price")->chunk(0));
-                int64_t length = id_array->length();
-                for (int64_t i = 0; i < id_array->length(); i++) {
-                    id_to_price[id_array->Value(i)] = price_array->Value(i);
-                }
-            }
             
             std::vector<bool> bitmap = {};