fix Milvus crash when searching and building index simultaneously using SQ8H (#794)

* #715 fix Milvus crash when searching and building index simultaneously using SQ8H

* #715 fix update

CHANGELOG.md

@@ -5,6 +5,7 @@ Please mark all change in change log and use the issue from GitHub
 # Milvus 0.7.0 (TBD)
 
 ## Bug
+- \#715 - Milvus crash when searching and building index simultaneously using SQ8H
 - \#744 - Don't return partition table for show_tables
 
 ## Feature

core/src/index/knowhere/knowhere/index/vector_index/IndexIVFSQHybrid.cpp

@@ -19,6 +19,7 @@
 #include "knowhere/index/vector_index/IndexIVFSQHybrid.h"
 #include "knowhere/adapter/VectorAdapter.h"
 #include "knowhere/common/Exception.h"
+#include "knowhere/index/vector_index/helpers/FaissIO.h"
 
 #include <utility>
 
@@ -77,6 +78,13 @@ IVFSQHybrid::CopyGpuToCpu(const Config& config) {
     faiss::Index* device_index = index_.get();
     faiss::Index* host_index = faiss::gpu::index_gpu_to_cpu(device_index);
 
+    if (auto* ivf_index = dynamic_cast<faiss::IndexIVF*>(host_index)) {
+        if (ivf_index != nullptr) {
+            ivf_index->to_readonly();
+        }
+        ivf_index->backup_quantizer();
+    }
+
     std::shared_ptr<faiss::Index> new_index;
     new_index.reset(host_index);
     return std::make_shared<IVFSQHybrid>(new_index);
@@ -287,6 +295,30 @@ IVFSQHybrid::set_index_model(IndexModelPtr model) {
     }
 }
 
+BinarySet
+IVFSQHybrid::SerializeImpl() {
+    if (!index_ || !index_->is_trained) {
+        KNOWHERE_THROW_MSG("index not initialize or trained");
+    }
+
+    if (gpu_mode == 0) {
+        MemoryIOWriter writer;
+        faiss::write_index(index_.get(), &writer);
+
+        auto data = std::make_shared<uint8_t>();
+        data.reset(writer.data_);
+
+        BinarySet res_set;
+        res_set.Append("IVF", data, writer.rp);
+
+        return res_set;
+    } else if (gpu_mode == 2) {
+        return GPUIVF::SerializeImpl();
+    } else {
+        KNOWHERE_THROW_MSG("Can't serialize IVFSQ8Hybrid");
+    }
+}
+
 FaissIVFQuantizer::~FaissIVFQuantizer() {
     if (quantizer != nullptr) {
         delete quantizer;

core/src/index/knowhere/knowhere/index/vector_index/IndexIVFSQHybrid.h

@@ -81,6 +81,9 @@ class IVFSQHybrid : public GPUIVFSQ {
     VectorIndexPtr
     CopyCpuToGpu(const int64_t& device_id, const Config& config) override;
 
+    BinarySet
+    SerializeImpl();
+
  protected:
     void
     search_impl(int64_t n, const float* data, int64_t k, float* distances, int64_t* labels, const Config& cfg) override;