diff --git a/src/index/hnsw/faiss_hnsw.cc b/src/index/hnsw/faiss_hnsw.cc
index 1e89942ba..3d5573df8 100644
--- a/src/index/hnsw/faiss_hnsw.cc
+++ b/src/index/hnsw/faiss_hnsw.cc
@@ -736,17 +736,24 @@ class FaissHnswIterator : public IndexIterator {
 
     void
     next_batch(std::function<void(const std::vector<DistId>&)> batch_handler) override {
-        if (workspace.bitset.empty()) {
-            using filter_type = faiss::IDSelectorAll;
-            filter_type sel;
-
-            next_batch(batch_handler, sel);
-        } else {
-            using filter_type = knowhere::BitsetViewIDSelector;
-            filter_type sel(workspace.bitset);
+        std::vector<folly::Future<folly::Unit>> futs;
+        futs.reserve(1);
+        std::shared_ptr<ThreadPool> search_pool = ThreadPool::GetGlobalSearchThreadPool();
+        futs.emplace_back(search_pool->push([&] {
+            ThreadPool::ScopedSearchOmpSetter setter(1);
+            if (workspace.bitset.empty()) {
+                using filter_type = faiss::IDSelectorAll;
+                filter_type sel;
+
+                next_batch(batch_handler, sel);
+            } else {
+                using filter_type = knowhere::BitsetViewIDSelector;
+                filter_type sel(workspace.bitset);
 
-            next_batch(batch_handler, sel);
-        }
+                next_batch(batch_handler, sel);
+            }
+        }));
+        WaitAllSuccess(futs);
     }
 
     float
@@ -1231,6 +1238,7 @@ class BaseFaissRegularIndexHNSWNode : public BaseFaissRegularIndexNode {
             futs.reserve(n_queries);
             for (int64_t i = 0; i < n_queries; i++) {
                 futs.emplace_back(search_pool->push([&, idx = i] {
+                    ThreadPool::ScopedSearchOmpSetter setter(1);
                     // The query data is always cloned
                     std::unique_ptr<float[]> cur_query = std::make_unique<float[]>(dim);
 
diff --git a/src/index/ivf/ivf.cc b/src/index/ivf/ivf.cc
index 8d43db8a0..a9e617c31 100644
--- a/src/index/ivf/ivf.cc
+++ b/src/index/ivf/ivf.cc
@@ -334,9 +334,15 @@ class IvfIndexNode : public IndexNode {
      protected:
         void
         next_batch(std::function<void(const std::vector<DistId>&)> batch_handler) override {
-            index_->getIteratorNextBatch(workspace_.get(), res_.size());
-            batch_handler(workspace_->dists);
-            workspace_->dists.clear();
+            std::vector<folly::Future<folly::Unit>> futs;
+            futs.reserve(1);
+            futs.emplace_back(search_pool_->push([&] {
+                ThreadPool::ScopedSearchOmpSetter setter(1);
+                index_->getIteratorNextBatch(workspace_.get(), res_.size());
+                batch_handler(workspace_->dists);
+                workspace_->dists.clear();
+            }));
+            WaitAllSuccess(futs);
         }
 
      private:
@@ -947,6 +953,7 @@ IvfIndexNode<DataType, IndexType>::AnnIterator(const DataSetPtr dataset, std::un
             futs.reserve(rows);
             for (int i = 0; i < rows; ++i) {
                 futs.emplace_back(search_pool_->push([&, index = i] {
+                    ThreadPool::ScopedSearchOmpSetter setter(1);
                     auto cur_query = (const float*)data + index * dim;
                     // if cosine, need normalize
                     std::unique_ptr<float[]> copied_query = nullptr;