diff --git a/core/src/config/ServerConfig.cpp b/core/src/config/ServerConfig.cpp
index 8e2cc5bef341e3167b3d4c03ccd92e61f150cba7..8cf00a14823201352e930057f6edc3f141c0ec7a 100644
--- a/core/src/config/ServerConfig.cpp
+++ b/core/src/config/ServerConfig.cpp
@@ -58,7 +58,10 @@ ParseGPUDevices(const std::string& str) {
         device_set.insert(std::stoll(device.substr(3)));
     }
 
-    for (auto dev : device_set) devices.push_back(dev);
+    devices.reserve(device_set.size());
+    for (auto dev : device_set) {
+        devices.push_back(dev);
+    }
     return devices;
 }
 
diff --git a/core/src/db/DBImpl.cpp b/core/src/db/DBImpl.cpp
index 4d61ad31c8bfb35fb9ec8531285a1338b274ae26..b871865e678a7d3beb4d33e6cc27126a02212ab2 100644
--- a/core/src/db/DBImpl.cpp
+++ b/core/src/db/DBImpl.cpp
@@ -699,7 +699,7 @@ DBImpl::ListIDInSegment(const std::string& collection_name, int64_t segment_id,
         std::vector<offset_t> temp_ids;
         temp_ids.reserve(delete_ids.size());
         std::copy(delete_ids.begin(), delete_ids.end(), std::back_inserter(temp_ids));
-        std::sort(temp_ids.begin(), temp_ids.end(), std::greater<offset_t>());
+        std::sort(temp_ids.begin(), temp_ids.end(), std::greater<>());
         for (auto offset : temp_ids) {
             entity_ids.erase(entity_ids.begin() + offset, entity_ids.begin() + offset + 1);
         }
@@ -979,7 +979,7 @@ DBImpl::BackgroundBuildIndexTask(std::vector<std::string> collection_names) {
 
     std::unique_lock<std::mutex> lock(build_index_mutex_);
 
-    for (auto collection_name : collection_names) {
+    for (const auto& collection_name : collection_names) {
         snapshot::ScopedSnapshotT latest_ss;
         auto status = snapshot::Snapshots::GetInstance().GetSnapshot(latest_ss, collection_name);
         if (!status.ok()) {
diff --git a/core/src/db/SnapshotHandlers.cpp b/core/src/db/SnapshotHandlers.cpp
index bbadda65f7b368de2d34c858de783423a0f2f68e..f29912fb5ad2035c4cb705c4a146314077713f15 100644
--- a/core/src/db/SnapshotHandlers.cpp
+++ b/core/src/db/SnapshotHandlers.cpp
@@ -105,7 +105,7 @@ GetEntityByIdSegmentHandler::Handle(const snapshot::SegmentPtr& segment) {
 
     std::vector<idx_t> ids_in_this_segment;
     std::vector<int64_t> offsets;
-    for (IDNumbers::iterator it = ids_left_.begin(); it != ids_left_.end();) {
+    for (auto it = ids_left_.begin(); it != ids_left_.end();) {
         idx_t id = *it;
         // fast check using bloom filter
         if (!id_bloom_filter_ptr->Check(id)) {
diff --git a/core/src/db/SnapshotUtils.cpp b/core/src/db/SnapshotUtils.cpp
index e1e1bbd391cafb9dff44c0bf413367a34afe0141..5086da578fdaf03c1787c1f56942abbdb39a7b95 100644
--- a/core/src/db/SnapshotUtils.cpp
+++ b/core/src/db/SnapshotUtils.cpp
@@ -210,7 +210,7 @@ GetSnapshotInfo(const std::string& collection_name, milvus::json& json_info) {
             const engine::snapshot::FieldPtr& field = iter.second->GetField();
 
             auto& elements = iter.second->GetElementVistors();
-            for (auto pair : elements) {
+            for (const auto& pair : elements) {
                 if (pair.second == nullptr || pair.second->GetElement() == nullptr) {
                     continue;
                 }
diff --git a/core/src/db/insert/MemSegment.cpp b/core/src/db/insert/MemSegment.cpp
index 47ff76a46762b90ec8f7898b29ea97fd2150fc80..beab06db51b0ee3d61af39723cfb88bd0f2e456d 100644
--- a/core/src/db/insert/MemSegment.cpp
+++ b/core/src/db/insert/MemSegment.cpp
@@ -228,7 +228,7 @@ MemSegment::ApplyDeleteToMem() {
             if (uid_data->data_.size() / sizeof(idx_t) != chunk->count_) {
                 continue;  // invalid uid data?
             }
-            idx_t* uid = (idx_t*)(uid_data->data_.data());
+            auto uid = reinterpret_cast<idx_t*>(uid_data->data_.data());
 
             // calculte delete offsets
             std::vector<offset_t> offsets;
diff --git a/core/src/db/snapshot/CompoundOperations.cpp b/core/src/db/snapshot/CompoundOperations.cpp
index 97d8a8dc2dd4653214e5b8ad33c60d389a4d1537..2402fa5def99ac164a5ab84814b5991f559e1e54 100644
--- a/core/src/db/snapshot/CompoundOperations.cpp
+++ b/core/src/db/snapshot/CompoundOperations.cpp
@@ -416,7 +416,7 @@ DropAllIndexOperation::PreCheck() {
         return Status(SS_INVALID_CONTEX_ERROR, emsg.str());
     }
 
-    for (auto stale_fe : context_.stale_field_elements) {
+    for (const auto& stale_fe : context_.stale_field_elements) {
         if (!GetStartedSS()->GetResource<FieldElement>(stale_fe->GetID())) {
             std::stringstream emsg;
             emsg << GetRepr() << ".  Specified field element " << stale_fe->GetName();
diff --git a/core/src/scheduler/TaskTable.cpp b/core/src/scheduler/TaskTable.cpp
index 370889ecd9ecdb771d5673e97b8be3f9c9dbe910..d083bf5d4c848a6896ed7ffe46fcb135e371ba4c 100644
--- a/core/src/scheduler/TaskTable.cpp
+++ b/core/src/scheduler/TaskTable.cpp
@@ -190,6 +190,8 @@ TaskTable::PickToLoad(uint64_t limit) {
             cross = true;
             indexes.push_back(index);
             ++pick_count;
+        } else {
+            cross = true;
         }
     }
     // rc.ElapseFromBegin("PickToLoad ");
@@ -262,6 +264,8 @@ TaskTable::PickToExecute(uint64_t limit) {
             cross = true;
             indexes.push_back(index);
             ++pick_count;
+        } else {
+            cross = true;
         }
     }
     // rc.ElapseFromBegin("PickToExecute ");
diff --git a/core/src/server/delivery/request/LoadCollectionReq.cpp b/core/src/server/delivery/request/LoadCollectionReq.cpp
index 7b74885d3912609564890750fc9fb703218b6ac6..b8579d69e30f497f0352e8455fc887c6f7b9e0f6 100644
--- a/core/src/server/delivery/request/LoadCollectionReq.cpp
+++ b/core/src/server/delivery/request/LoadCollectionReq.cpp
@@ -50,7 +50,7 @@ LoadCollectionReq::OnExecute() {
 
         // TODO(yukun): if PreloadCollection interface needs to add field names as params
         std::vector<std::string> field_names;
-        for (auto field_it : fields_schema) {
+        for (const auto& field_it : fields_schema) {
             field_names.emplace_back(field_it.first->GetName());
         }
 
diff --git a/core/src/server/grpc_impl/GrpcRequestHandler.cpp b/core/src/server/grpc_impl/GrpcRequestHandler.cpp
index d41adb6922c18db718fa5ec041f3f5ca65a903bc..a93810d3544bd07983bf28c210a77d6b3772e1c2 100644
--- a/core/src/server/grpc_impl/GrpcRequestHandler.cpp
+++ b/core/src/server/grpc_impl/GrpcRequestHandler.cpp
@@ -367,7 +367,7 @@ ConstructEntityResults(const std::vector<engine::AttrsData>& attrs, const std::v
 
     std::string vector_field_name;
     bool set_valid_row = false;
-    for (auto field_name : field_names) {
+    for (const auto& field_name : field_names) {
         if (!attrs.empty()) {
             if (attrs[0].attr_type_.find(field_name) != attrs[0].attr_type_.end()) {
                 auto grpc_field = response->add_fields();
@@ -1252,6 +1252,7 @@ GrpcRequestHandler::Flush(::grpc::ServerContext* context, const ::milvus::grpc::
     LOG_SERVER_INFO_ << LogOut("Request [%s] %s begin.", GetContext(context)->ReqID().c_str(), __func__);
 
     std::vector<std::string> collection_names;
+    collection_names.reserve(collection_names.size());
     for (int32_t i = 0; i < request->collection_name_array().size(); i++) {
         collection_names.push_back(request->collection_name_array(i));
     }
diff --git a/core/src/server/web_impl/handler/WebRequestHandler.cpp b/core/src/server/web_impl/handler/WebRequestHandler.cpp
index 709e787a4aaa9760ddd7accd4cf51048a61db89d..3859161d1252269b103948916fbd61762746e680 100644
--- a/core/src/server/web_impl/handler/WebRequestHandler.cpp
+++ b/core/src/server/web_impl/handler/WebRequestHandler.cpp
@@ -90,7 +90,7 @@ CopyStructuredData(const nlohmann::json& json, std::vector<uint8_t>& raw) {
     values.resize(size);
     raw.resize(size * sizeof(T));
     size_t offset = 0;
-    for (auto data : json) {
+    for (const auto& data : json) {
         values[offset] = data.get<T>();
         ++offset;
     }
@@ -1770,6 +1770,8 @@ WebRequestHandler::GetEntity(const milvus::server::web::OString& collection_name
         std::vector<std::string> ids;
         StringHelpFunctions::SplitStringByDelimeter(query_ids->c_str(), ",", ids);
         std::vector<int64_t> entity_ids;
+
+        entity_ids.reserve(ids.size());
         for (auto& id : ids) {
             entity_ids.push_back(std::stol(id));
         }
diff --git a/core/src/utils/CommonUtil.cpp b/core/src/utils/CommonUtil.cpp
index c19121a1d8e672d01fee47a76ef9c8fdb4545c51..0ee80d0f72aac5d3c979ee68a28b61667a8ef1bd 100644
--- a/core/src/utils/CommonUtil.cpp
+++ b/core/src/utils/CommonUtil.cpp
@@ -84,7 +84,7 @@ RemoveDirectory(const std::string& path) {
             if (strcmp(dmsg->d_name, ".") != 0 && strcmp(dmsg->d_name, "..") != 0) {
                 snprintf(file_name, buf_size, folder_name.c_str(), dmsg->d_name);
                 std::string tmp = file_name;
-                if (tmp.find(".") == std::string::npos) {
+                if (tmp.find('.') == std::string::npos) {
                     RemoveDirectory(file_name);
                 }
                 remove(file_name);