diff --git a/src/kvstore/NebulaStore.cpp b/src/kvstore/NebulaStore.cpp
index ec53d1c0e57..43623e22ef0 100644
--- a/src/kvstore/NebulaStore.cpp
+++ b/src/kvstore/NebulaStore.cpp
@@ -608,6 +608,7 @@ void NebulaStore::ReleaseSnapshot(GraphSpaceID spaceId, PartitionID partId, cons
   if (!ok(ret)) {
     LOG(INFO) << "Failed to release snapshot for GraphSpaceID " << spaceId << " PartitionID"
               << partId;
+    return;
   }
   auto part = nebula::value(ret);
   return part->engine()->ReleaseSnapshot(snapshot);
diff --git a/src/tools/db-upgrade/DbUpgrader.cpp b/src/tools/db-upgrade/DbUpgrader.cpp
index bc0cefdc394..1666f24aa7a 100644
--- a/src/tools/db-upgrade/DbUpgrader.cpp
+++ b/src/tools/db-upgrade/DbUpgrader.cpp
@@ -219,7 +219,7 @@ void UpgraderSpace::runPartV1() {
               << partId;
     const auto& prefix = NebulaKeyUtilsV1::prefix(partId);
     std::unique_ptr<kvstore::KVIterator> iter;
-    auto retCode = readEngine_->prefix(prefix, nullptr, &iter);
+    auto retCode = readEngine_->prefix(prefix, &iter);
     if (retCode != nebula::cpp2::ErrorCode::SUCCEEDED) {
       LOG(ERROR) << "Space id " << spaceId_ << " part " << partId << " no found!";
       LOG(ERROR) << "Handle vertex/edge/index data in space id " << spaceId_ << " part id "
@@ -393,7 +393,7 @@ void UpgraderSpace::doProcessV1() {
     LOG(INFO) << "Start to handle system data in space id " << spaceId_;
     auto prefix = NebulaKeyUtilsV1::systemPrefix();
     std::unique_ptr<kvstore::KVIterator> iter;
-    auto retCode = readEngine_->prefix(prefix, nullptr, &iter);
+    auto retCode = readEngine_->prefix(prefix, &iter);
     if (retCode != nebula::cpp2::ErrorCode::SUCCEEDED) {
       LOG(ERROR) << "Space id " << spaceId_ << " get system data failed";
       LOG(ERROR) << "Handle system data in space id " << spaceId_ << " failed";
@@ -433,7 +433,7 @@ void UpgraderSpace::runPartV2() {
               << partId;
     auto prefix = NebulaKeyUtilsV2::partPrefix(partId);
     std::unique_ptr<kvstore::KVIterator> iter;
-    auto retCode = readEngine_->prefix(prefix, nullptr, &iter);
+    auto retCode = readEngine_->prefix(prefix, &iter);
     if (retCode != nebula::cpp2::ErrorCode::SUCCEEDED) {
       LOG(ERROR) << "Space id " << spaceId_ << " part " << partId << " no found!";
       LOG(ERROR) << "Handle vertex/edge/index data in space id " << spaceId_ << " part id "
@@ -601,7 +601,7 @@ void UpgraderSpace::doProcessV2() {
     LOG(INFO) << "Start to handle system data in space id " << spaceId_;
     auto prefix = NebulaKeyUtilsV2::systemPrefix();
     std::unique_ptr<kvstore::KVIterator> iter;
-    auto retCode = readEngine_->prefix(prefix, nullptr, &iter);
+    auto retCode = readEngine_->prefix(prefix, &iter);
     if (retCode != nebula::cpp2::ErrorCode::SUCCEEDED) {
       LOG(ERROR) << "Space id " << spaceId_ << " get system data failed.";
       LOG(ERROR) << "Handle system data in space id " << spaceId_ << " failed.";
@@ -894,7 +894,7 @@ void UpgraderSpace::runPartV3() {
               << partId;
     auto prefix = NebulaKeyUtilsV3::partTagPrefix(partId);
     std::unique_ptr<kvstore::KVIterator> iter;
-    auto retCode = readEngine_->prefix(prefix, nullptr, &iter);
+    auto retCode = readEngine_->prefix(prefix, &iter);
     if (retCode != nebula::cpp2::ErrorCode::SUCCEEDED) {
       LOG(ERROR) << "Space id " << spaceId_ << " part " << partId << " no found!";
       LOG(ERROR) << "Handle vertex/edge/index data in space id " << spaceId_ << " part id "