add db setting file

Former-commit-id: 184bf9c48a5b659a85a11b09aa694165ee6b7b61

cpp/src/db/db_connection.cpp

+////////////////////////////////////////////////////////////////////////////////
+// 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 "db_connection.h"
+
+#include <string>
+#include <iostream>
+#include <thread>
+
+namespace zilliz {
+namespace vecwise {
+namespace engine {
+
+using std::cout;
+using std::endl;
+using std::string;
+
+string storage_file_name = "default.sqlite"
+
+DbPtr connect() {
+    DbPtr temp = std::make_shared<SqliteDB>(initStorage(storage_file_name));
+    temp->sync_schema();
+    temp->open_forever(); // thread safe option
+    temp->pragma.journal_mode(journal_mode::WAL); // WAL => write ahead log
+    return temp;
+}
+
+SqliteDBPtr Connection::connect_ = connect();
+
+}
+}
+}

cpp/src/db/db_connection.h

+////////////////////////////////////////////////////////////////////////////////
+// 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.
+////////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+
+namespace zilliz {
+namespace vecwise {
+namespace engine {
+
+struct GroupSchema {
+    size_t id;
+    std::string group_id;
+    size_t files_cnt = 0;
+    uint16_t dimension;
+    std::string location = "";
+    std::string next_file_location = "";
+}; // GroupSchema
+
+
+struct GroupFileSchema {
+    typedef enum {
+        RAW,
+        INDEX
+    } FILE_TYPE;
+
+    size_t id;
+    std::string group_id;
+    std::string file_id;
+    int files_type = RAW;
+    size_t rows;
+    std::string location = "";
+}; // GroupFileSchema
+
+inline auto initStorage(const std::string &path) {
+    return make_storage(path,
+                        make_table("COMPANY",
+                                   make_column("ID", &Employee::id, primary_key()),
+                                   make_column("AGE", &Employee::age)));
+}
+
+using SqliteDB = decltype(initStorage(""));
+using SqliteDBPtr= std::shared_ptr<Db>;
+
+class Connection {
+protected:
+    static SqliteDBPtr connect_;
+};
+
+}
+}
+}
+
+
+
+