diff --git a/core/coverage.sh b/core/coverage.sh
index 55c70d7e8d..74f9f4219d 100755
--- a/core/coverage.sh
+++ b/core/coverage.sh
@@ -114,15 +114,15 @@ ${LCOV_CMD} -r "${FILE_INFO_OUTPUT}" -o "${FILE_INFO_OUTPUT_NEW}" \
     "/usr/*" \
     "*/boost/*" \
     "*/cmake_build/*_ep-prefix/*" \
-    "src/index/cmake_build*" \
-    "src/index/thirdparty*" \
-    "src/grpc*"\
-    "src/metrics/MetricBase.h"\
-    "src/server/Server.cpp"\
-    "src/server/DBWrapper.cpp"\
-    "src/server/grpc_impl/GrpcServer.cpp"\
-    "src/utils/easylogging++.h"\
-    "src/utils/easylogging++.cc"\
+    "*/src/index/cmake_build*" \
+    "*/src/index/thirdparty*" \
+    "*/src/grpc*" \
+    "*/src/metrics/MetricBase.h" \
+    "*/src/server/Server.cpp" \
+    "*/src/server/DBWrapper.cpp" \
+    "*/src/server/grpc_impl/GrpcServer.cpp" \
+    "*/src/utils/easylogging++.h" \
+    "*/src/utils/easylogging++.cc"
 
 # gen html report
 ${LCOV_GEN_CMD} "${FILE_INFO_OUTPUT_NEW}" --output-directory ${DIR_LCOV_OUTPUT}/
diff --git a/core/src/db/engine/ExecutionEngineImpl.cpp b/core/src/db/engine/ExecutionEngineImpl.cpp
index 862c1026d2..0f893f82c7 100644
--- a/core/src/db/engine/ExecutionEngineImpl.cpp
+++ b/core/src/db/engine/ExecutionEngineImpl.cpp
@@ -164,6 +164,9 @@ ExecutionEngineImpl::HybridLoad() const {
         quantizer_conf->mode = 1;
         quantizer_conf->gpu_id = best_device_id;
         auto quantizer = index_->LoadQuantizer(quantizer_conf);
+        if (quantizer == nullptr) {
+            ENGINE_LOG_ERROR << "quantizer is nullptr";
+        }
         index_->SetQuantizer(quantizer);
         auto cache_quantizer = std::make_shared<CachedQuantizer>(quantizer);
         cache::GpuCacheMgr::GetInstance(best_device_id)->InsertItem(key, cache_quantizer);
diff --git a/core/src/wrapper/VecIndex.h b/core/src/wrapper/VecIndex.h
index 05da9ccc03..36104b2107 100644
--- a/core/src/wrapper/VecIndex.h
+++ b/core/src/wrapper/VecIndex.h
@@ -25,6 +25,7 @@
 #include "knowhere/common/BinarySet.h"
 #include "knowhere/common/Config.h"
 #include "knowhere/index/vector_index/Quantizer.h"
+#include "utils/Log.h"
 #include "utils/Status.h"
 
 namespace milvus {
@@ -101,6 +102,7 @@ class VecIndex : public cache::DataObj {
     ////////////////
     virtual knowhere::QuantizerPtr
     LoadQuantizer(const Config& conf) {
+        ENGINE_LOG_ERROR << "LoadQuantizer virtual funciton called.";
         return nullptr;
     }