diff --git a/cpp/src/db/DB.cpp b/cpp/src/db/DB.cpp
index 5baa09bd71..610e353358 100644
--- a/cpp/src/db/DB.cpp
+++ b/cpp/src/db/DB.cpp
@@ -7,8 +7,6 @@
 #include "DBImpl.h"
 #include "DBMetaImpl.h"
 #include "Env.h"
-/* #include "FaissExecutionEngine.h" */
-/* #include "Traits.h" */
 #include "Factories.h"
 
 namespace zilliz {
diff --git a/cpp/src/db/DBImpl.h b/cpp/src/db/DBImpl.h
index 523922d3d3..6d91a91c7e 100644
--- a/cpp/src/db/DBImpl.h
+++ b/cpp/src/db/DBImpl.h
@@ -5,15 +5,15 @@
  ******************************************************************************/
 #pragma once
 
+#include "DB.h"
+#include "MemManager.h"
+#include "Types.h"
+#include "Traits.h"
+
 #include <mutex>
 #include <condition_variable>
 #include <memory>
 #include <atomic>
-#include "DB.h"
-#include "MemManager.h"
-#include "Types.h"
-#include "FaissExecutionEngine.h"
-#include "Traits.h"
 
 namespace zilliz {
 namespace vecwise {
@@ -95,4 +95,4 @@ private:
 } // namespace vecwise
 } // namespace zilliz
 
-#include "DBImpl.cpp"
+#include "DBImpl.inl"
diff --git a/cpp/src/db/DBImpl.cpp b/cpp/src/db/DBImpl.inl
similarity index 99%
rename from cpp/src/db/DBImpl.cpp
rename to cpp/src/db/DBImpl.inl
index 90f0bf5c5d..7adf80d4fe 100644
--- a/cpp/src/db/DBImpl.cpp
+++ b/cpp/src/db/DBImpl.inl
@@ -3,8 +3,11 @@
  * Unauthorized copying of this file, via any medium is strictly prohibited.
  * Proprietary and confidential.
  ******************************************************************************/
-#ifndef DBIMPL_CPP__
-#define DBIMPL_CPP__
+#pragma once
+
+#include "DBImpl.h"
+#include "DBMetaImpl.h"
+#include "Env.h"
 
 #include <assert.h>
 #include <chrono>
@@ -14,10 +17,6 @@
 #include <easylogging++.h>
 #include <cache/CpuCacheMgr.h>
 
-#include "DBImpl.h"
-#include "DBMetaImpl.h"
-#include "Env.h"
-
 namespace zilliz {
 namespace vecwise {
 namespace engine {
@@ -435,5 +434,3 @@ DBImpl<EngineT>::~DBImpl() {
 } // namespace engine
 } // namespace vecwise
 } // namespace zilliz
-
-#endif
diff --git a/cpp/src/db/DBMetaImpl.cpp b/cpp/src/db/DBMetaImpl.cpp
index f6cc3a0ecd..69f0fc56a5 100644
--- a/cpp/src/db/DBMetaImpl.cpp
+++ b/cpp/src/db/DBMetaImpl.cpp
@@ -71,7 +71,7 @@ void DBMetaImpl::GetTableFilePath(TableFileSchema& group_file) {
 Status DBMetaImpl::NextTableId(std::string& table_id) {
     std::stringstream ss;
     SimpleIDGenerator g;
-    ss << g.getNextIDNumber();
+    ss << g.GetNextIDNumber();
     table_id = ss.str();
     return Status::OK();
 }
@@ -79,7 +79,7 @@ Status DBMetaImpl::NextTableId(std::string& table_id) {
 Status DBMetaImpl::NextFileId(std::string& file_id) {
     std::stringstream ss;
     SimpleIDGenerator g;
-    ss << g.getNextIDNumber();
+    ss << g.GetNextIDNumber();
     file_id = ss.str();
     return Status::OK();
 }
diff --git a/cpp/src/db/Factories.cpp b/cpp/src/db/Factories.cpp
index 87aae6afbb..191d3dbae5 100644
--- a/cpp/src/db/Factories.cpp
+++ b/cpp/src/db/Factories.cpp
@@ -3,6 +3,11 @@
 // Unauthorized copying of this file, via any medium is strictly prohibited.
 // Proprietary and confidential.
 ////////////////////////////////////////////////////////////////////////////////
+#include "Factories.h"
+#include "DBImpl.h"
+#include "FaissExecutionEngine.h"
+#include "Traits.h"
+
 #include <stdlib.h>
 #include <time.h>
 #include <sstream>
@@ -11,12 +16,6 @@
 #include <assert.h>
 #include <easylogging++.h>
 
-#include "Factories.h"
-#include "DBImpl.h"
-#include "FaissExecutionEngine.h"
-#include "Traits.h"
-
-
 namespace zilliz {
 namespace vecwise {
 namespace engine {
diff --git a/cpp/src/db/Factories.h b/cpp/src/db/Factories.h
index 3c9c3a99aa..0e9ab71bb1 100644
--- a/cpp/src/db/Factories.h
+++ b/cpp/src/db/Factories.h
@@ -3,15 +3,15 @@
 // Unauthorized copying of this file, via any medium is strictly prohibited.
 // Proprietary and confidential.
 ////////////////////////////////////////////////////////////////////////////////
-
 #pragma once
 
-#include <string>
-#include <memory>
 #include "DB.h"
 #include "DBMetaImpl.h"
 #include "Options.h"
 
+#include <string>
+#include <memory>
+
 namespace zilliz {
 namespace vecwise {
 namespace engine {
diff --git a/cpp/src/db/IDGenerator.cpp b/cpp/src/db/IDGenerator.cpp
index 633ee5fe69..d6e71091e6 100644
--- a/cpp/src/db/IDGenerator.cpp
+++ b/cpp/src/db/IDGenerator.cpp
@@ -3,30 +3,29 @@
 // Unauthorized copying of this file, via any medium is strictly prohibited.
 // Proprietary and confidential.
 ////////////////////////////////////////////////////////////////////////////////
+#include "IDGenerator.h"
+
 #include <chrono>
 #include <assert.h>
 #include <iostream>
 
-#include "IDGenerator.h"
-
-
 namespace zilliz {
 namespace vecwise {
 namespace engine {
 
 IDGenerator::~IDGenerator() {}
 
-IDNumber SimpleIDGenerator::getNextIDNumber() {
+IDNumber SimpleIDGenerator::GetNextIDNumber() {
     auto now = std::chrono::system_clock::now();
     auto micros = std::chrono::duration_cast<std::chrono::microseconds>(
             now.time_since_epoch()).count();
     return micros * MAX_IDS_PER_MICRO;
 }
 
-void SimpleIDGenerator::nextIDNumbers(size_t n, IDNumbers& ids) {
+void SimpleIDGenerator::NextIDNumbers(size_t n, IDNumbers& ids) {
     if (n > MAX_IDS_PER_MICRO) {
-        nextIDNumbers(n-MAX_IDS_PER_MICRO, ids);
-        nextIDNumbers(MAX_IDS_PER_MICRO, ids);
+        NextIDNumbers(n-MAX_IDS_PER_MICRO, ids);
+        NextIDNumbers(MAX_IDS_PER_MICRO, ids);
         return;
     }
     if (n <= 0) {
@@ -41,12 +40,11 @@ void SimpleIDGenerator::nextIDNumbers(size_t n, IDNumbers& ids) {
     for (int pos=0; pos<n; ++pos) {
         ids.push_back(micros+pos);
     }
-
 }
 
-void SimpleIDGenerator::getNextIDNumbers(size_t n, IDNumbers& ids) {
+void SimpleIDGenerator::GetNextIDNumbers(size_t n, IDNumbers& ids) {
     ids.clear();
-    nextIDNumbers(n, ids);
+    NextIDNumbers(n, ids);
 }
 
 
diff --git a/cpp/src/db/IDGenerator.h b/cpp/src/db/IDGenerator.h
index 4b826610da..e084e2b146 100644
--- a/cpp/src/db/IDGenerator.h
+++ b/cpp/src/db/IDGenerator.h
@@ -5,17 +5,19 @@
 ////////////////////////////////////////////////////////////////////////////////
 #pragma once
 
-#include <vector>
 #include "Types.h"
 
+#include <cstddef>
+#include <vector>
+
 namespace zilliz {
 namespace vecwise {
 namespace engine {
 
 class IDGenerator {
 public:
-    virtual IDNumber getNextIDNumber() = 0;
-    virtual void getNextIDNumbers(size_t n, IDNumbers& ids) = 0;
+    virtual IDNumber GetNextIDNumber() = 0;
+    virtual void GetNextIDNumbers(size_t n, IDNumbers& ids) = 0;
 
     virtual ~IDGenerator();
 
@@ -24,11 +26,11 @@ public:
 
 class SimpleIDGenerator : public IDGenerator {
 public:
-    virtual IDNumber getNextIDNumber() override;
-    virtual void getNextIDNumbers(size_t n, IDNumbers& ids) override;
+    virtual IDNumber GetNextIDNumber() override;
+    virtual void GetNextIDNumbers(size_t n, IDNumbers& ids) override;
 
 private:
-    void nextIDNumbers(size_t n, IDNumbers& ids);
+    void NextIDNumbers(size_t n, IDNumbers& ids);
     const size_t MAX_IDS_PER_MICRO = 1000;
 
 }; // SimpleIDGenerator
diff --git a/cpp/src/db/MemManager.h b/cpp/src/db/MemManager.h
index b6e4b86c89..f45f8c34b2 100644
--- a/cpp/src/db/MemManager.h
+++ b/cpp/src/db/MemManager.h
@@ -5,15 +5,15 @@
  ******************************************************************************/
 #pragma once
 
+#include "IDGenerator.h"
+#include "Status.h"
+#include "Meta.h"
+
 #include <map>
 #include <string>
 #include <ctime>
 #include <memory>
 #include <mutex>
-#include "IDGenerator.h"
-#include "Status.h"
-#include "Meta.h"
-
 
 namespace zilliz {
 namespace vecwise {
@@ -96,4 +96,4 @@ private:
 } // namespace engine
 } // namespace vecwise
 } // namespace zilliz
-#include "MemManager.cpp"
+#include "MemManager.inl"
diff --git a/cpp/src/db/MemManager.cpp b/cpp/src/db/MemManager.inl
similarity index 97%
rename from cpp/src/db/MemManager.cpp
rename to cpp/src/db/MemManager.inl
index 03ed3de1f3..82efd63d24 100644
--- a/cpp/src/db/MemManager.cpp
+++ b/cpp/src/db/MemManager.inl
@@ -3,18 +3,16 @@
  * Unauthorized copying of this file, via any medium is strictly prohibited.
  * Proprietary and confidential.
  ******************************************************************************/
-#ifndef MEMMANGE_CPP__
-#define MEMMANGE_CPP__
-
-#include <iostream>
-#include <sstream>
-#include <thread>
-#include <easylogging++.h>
+#pragma once
 
 #include "MemManager.h"
 #include "Meta.h"
 #include "MetaConsts.h"
 
+#include <iostream>
+#include <sstream>
+#include <thread>
+#include <easylogging++.h>
 
 namespace zilliz {
 namespace vecwise {
@@ -32,7 +30,7 @@ MemVectors<EngineT>::MemVectors(const std::shared_ptr<meta::Meta>& meta_ptr,
 
 template<typename EngineT>
 void MemVectors<EngineT>::add(size_t n_, const float* vectors_, IDNumbers& vector_ids_) {
-    _pIdGenerator->getNextIDNumbers(n_, vector_ids_);
+    _pIdGenerator->GetNextIDNumbers(n_, vector_ids_);
     pEE_->AddWithIds(n_, vectors_, vector_ids_.data());
 }
 
@@ -148,5 +146,3 @@ Status MemManager<EngineT>::serialize(std::vector<std::string>& table_ids) {
 } // namespace engine
 } // namespace vecwise
 } // namespace zilliz
-
-#endif
diff --git a/cpp/src/db/Utils.cpp b/cpp/src/db/Utils.cpp
index e459bab4bb..9b40152587 100644
--- a/cpp/src/db/Utils.cpp
+++ b/cpp/src/db/Utils.cpp
@@ -3,9 +3,9 @@
  * Unauthorized copying of this file, via any medium is strictly prohibited.
  * Proprietary and confidential.
  ******************************************************************************/
+#include "Utils.h"
 
 #include <chrono>
-#include "Utils.h"
 
 namespace zilliz {
 namespace vecwise {