diff --git a/cpp/src/db/DB.cpp b/cpp/src/db/DB.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..b30f48146454c56d591167f5ce3e87015e8713d0
--- /dev/null
+++ b/cpp/src/db/DB.cpp
@@ -0,0 +1,29 @@
+/*******************************************************************************
+ * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
+ * Unauthorized copying of this file, via any medium is strictly prohibited.
+ * Proprietary and confidential.
+ ******************************************************************************/
+
+#include "DBImpl.h"
+#include "DBMetaImpl.h"
+#include "Env.h"
+/* #include "FaissExecutionEngine.h" */
+/* #include "Traits.h" */
+#include "Factories.h"
+
+namespace zilliz {
+namespace vecwise {
+namespace engine {
+
+DB::~DB() {}
+
+void DB::Open(const Options& options, DB** dbptr) {
+    *dbptr = nullptr;
+    /* *dbptr = new DBImpl<FaissExecutionEngine<IVFIndexTrait>>(options); */
+    *dbptr = DBFactory::Build(options);
+    return;
+}
+
+} // namespace engine
+} // namespace vecwise
+} // namespace zilliz
diff --git a/cpp/src/db/DBImpl.cpp b/cpp/src/db/DBImpl.cpp
index 10d1d58463419d9119a38c423918d488ee8f7d61..80f433e98b4e8d454fe28510e4d26c507ab4f736 100644
--- a/cpp/src/db/DBImpl.cpp
+++ b/cpp/src/db/DBImpl.cpp
@@ -3,6 +3,8 @@
  * Unauthorized copying of this file, via any medium is strictly prohibited.
  * Proprietary and confidential.
  ******************************************************************************/
+#ifndef DBIMPL_CPP__
+#define DBIMPL_CPP__
 
 #include <assert.h>
 #include <chrono>
@@ -16,8 +18,6 @@
 #include "DBImpl.h"
 #include "DBMetaImpl.h"
 #include "Env.h"
-#include "FaissExecutionEngine.h"
-#include "Traits.h"
 
 namespace zilliz {
 namespace vecwise {
@@ -408,18 +408,8 @@ DBImpl<EngineT>::~DBImpl() {
     _env->Stop();
 }
 
-/*
- *  DB
- */
-
-DB::~DB() {}
-
-void DB::Open(const Options& options, DB** dbptr) {
-    *dbptr = nullptr;
-    *dbptr = new DBImpl<FaissExecutionEngine<IVFIndexTrait>>(options);
-    return;
-}
-
 } // namespace engine
 } // namespace vecwise
 } // namespace zilliz
+
+#endif
diff --git a/cpp/src/db/DBImpl.h b/cpp/src/db/DBImpl.h
index a03f7ffced80eb9c5df60e4212e32704409dc644..8896a1d48b3aa03ff97847e63f4866e89cc10982 100644
--- a/cpp/src/db/DBImpl.h
+++ b/cpp/src/db/DBImpl.h
@@ -12,6 +12,8 @@
 #include "DB.h"
 #include "MemManager.h"
 #include "Types.h"
+#include "FaissExecutionEngine.h"
+#include "Traits.h"
 
 namespace zilliz {
 namespace vecwise {
@@ -90,6 +92,9 @@ private:
 
 }; // DBImpl
 
+
 } // namespace engine
 } // namespace vecwise
 } // namespace zilliz
+
+#include "DBImpl.cpp"
diff --git a/cpp/src/db/Factories.cpp b/cpp/src/db/Factories.cpp
index 3f508a6a0512259621efbbf37b14f3fb400d5683..87aae6afbbac91a41836d4d7e52c31eaddd17614 100644
--- a/cpp/src/db/Factories.cpp
+++ b/cpp/src/db/Factories.cpp
@@ -6,8 +6,15 @@
 #include <stdlib.h>
 #include <time.h>
 #include <sstream>
+#include <iostream>
+#include <vector>
+#include <assert.h>
+#include <easylogging++.h>
 
 #include "Factories.h"
+#include "DBImpl.h"
+#include "FaissExecutionEngine.h"
+#include "Traits.h"
 
 
 namespace zilliz {
@@ -39,6 +46,30 @@ std::shared_ptr<meta::DBMetaImpl> DBMetaImplFactory::Build() {
     return std::shared_ptr<meta::DBMetaImpl>(new meta::DBMetaImpl(options));
 }
 
+std::shared_ptr<DB> DBFactory::Build(const std::string& db_type) {
+    auto options = OptionsFactory::Build();
+    auto db = DBFactory::Build(options, db_type);
+    return std::shared_ptr<DB>(db);
+}
+
+DB* DBFactory::Build(const Options& options, const std::string& db_type) {
+    std::stringstream ss(db_type);
+    std::string token;
+    std::vector<std::string> tokens;
+    while (std::getline(ss, token, ',')) {
+        tokens.push_back(token);
+    }
+
+    assert(tokens.size()==2);
+    assert(tokens[0]=="Faiss");
+    if (tokens[1] == "IVF") {
+        return new DBImpl<FaissExecutionEngine<IVFIndexTrait>>(options);
+    } else if (tokens[1] == "IDMap") {
+        return new DBImpl<FaissExecutionEngine<IDMapIndexTrait>>(options);
+    }
+    return nullptr;
+}
+
 } // namespace engine
 } // namespace vecwise
 } // namespace zilliz
diff --git a/cpp/src/db/Factories.h b/cpp/src/db/Factories.h
index ed584daa1e1f3483f4a77fe98297aa0e1342681e..3c9c3a99aa58192fbfff1280fbc677c165dee207 100644
--- a/cpp/src/db/Factories.h
+++ b/cpp/src/db/Factories.h
@@ -8,8 +8,9 @@
 
 #include <string>
 #include <memory>
-#include "db/DB.h"
+#include "DB.h"
 #include "DBMetaImpl.h"
+#include "Options.h"
 
 namespace zilliz {
 namespace vecwise {
@@ -27,6 +28,11 @@ struct DBMetaImplFactory {
     static std::shared_ptr<meta::DBMetaImpl> Build();
 };
 
+struct DBFactory {
+    static std::shared_ptr<DB> Build(const std::string& db_type = "Faiss,IVF");
+    static DB* Build(const Options&, const std::string& db_type = "Faiss,IVF");
+};
+
 } // namespace engine
 } // namespace vecwise
 } // namespace zilliz
diff --git a/cpp/unittest/db/utils.cpp b/cpp/unittest/db/utils.cpp
index 5080a88cfd055a63f68bbe9e5ee30e6c074c50a4..7188e89107b30fdf2b98837f834327101f240e51 100644
--- a/cpp/unittest/db/utils.cpp
+++ b/cpp/unittest/db/utils.cpp
@@ -33,12 +33,11 @@ void DBTest::SetUp() {
     InitLog();
     auto options = engine::OptionsFactory::Build();
     options.meta.path = "/tmp/vecwise_test";
-    engine::DB::Open(options, &db_);
+    db_ = engine::DBFactory::Build(options, "Faiss,IDMap");
 }
 
 void DBTest::TearDown() {
     delete db_;
-    db_ = nullptr;
     auto options = engine::OptionsFactory::Build();
     boost::filesystem::remove_all("/tmp/vecwise_test");
 }