多索引表 boost::multi_index多索引容器

Posted 2021-10-28 thefist11

1. 定义

一个名为multi_index_container的类模板，它支持构建容器来维护一个或多个具有不同排序和访问语义的索引。

每一个multi_index都相当于传统数据库的一个数据表（table），但将传统数据库的行与列的形式改为了单纯的列。也就是说multi_index是一个线性排列的表，只有一列，每一行都只存储一个对象。

1.1 Iterators（迭代器）

通过迭代器来操作数据表中的每个对象。

struct service_rec {
    uint64_t        pkey;           // 主键
    account_name    customer;       // 车主用户名
    uint32_t        service_date;   // 维修保养时间
    uint32_t        odometer;       // 车辆里程
 };

1.2.

#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
 
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/shared_ptr.hpp>
 
 
using namespace std;
 
//定义学生信息，同理可以使用结构定义
class student {
public:
	student(int id, string name, int score, string remark) :id(id), name(name), score(score), remark(remark) {
	}
 
	void print() const {
		cout << "id:" << id << " name:" << name << " score:" << score << endl;
	}
	int id;
	string name;
	int score;
	string remark;
};
 
// 如果要把student某个属性字段设置为搜索引擎，则需要定义用于排序的空结构体对象
struct _id {};
struct _name{};
struct _score {};
 
// 定义一个multi_index_container（多索引容器）
using student_table =
boost::multi_index::multi_index_container<
	student,
	boost::multi_index::indexed_by<
		boost::multi_index::ordered_unique<boost::multi_index::tag<_id>, BOOST_MULTI_INDEX_MEMBER(student, int, id)>,   // ID为唯一索引，类似主键
		boost::multi_index::ordered_non_unique<boost::multi_index::tag<_name>, BOOST_MULTI_INDEX_MEMBER(student, string, name)>, // 非唯一索引
		boost::multi_index::ordered_non_unique<boost::multi_index::tag<_score>, BOOST_MULTI_INDEX_MEMBER(student, int, score)>
	>
>;
 
int main() {
	// initialize data.
	student_table allStu;
	allStu.insert(student(1, "lili", 85, "hello"));
	allStu.insert(student(2, "liming", 90, "hello"));
	allStu.insert(student(3, "xiaoming", 65, "hello"));
	allStu.insert(student(4, "ergou", 80, "hello"));
	allStu.insert(student(5, "dagou", 60, "hello"));
 
	// sort
	student_table::index<_id>::type& sort_id = allStu.get<0>();
	cout << "sort by student id:" << endl;
	student_table::index<_id>::type::iterator iter_id = sort_id.begin();
	for (; iter_id != sort_id.end(); iter_id++) {
		iter_id->print();
	}
	cout << "\\n" << endl;
 
	student_table::index<_name>::type& sort_name = allStu.get<1>();
	cout << "sort by student name:" << endl;
	student_table::index<_name>::type::iterator iter_name = sort_name.begin();
	for (; iter_name != sort_name.end(); iter_name++) {
		iter_name->print();
	}
	cout << "\\n" << endl;
 
	student_table::index<_score>::type& sort_score = allStu.get<2>();
	cout << "sort by student score:" << endl;
	student_table::index<_score>::type::iterator iter_score = sort_score.begin();
	for (; iter_score != sort_score.end(); iter_score++) {
		iter_score->print();
	}
	cout << "\\n" << endl;
 
	// find
	student_table::index<_name>::type& find_name = allStu.get<_name>();
	student_table::index<_name>::type::iterator iter_ergou = find_name.find("ergou");
	if (iter_ergou != find_name.end()) {
		cout << "find a student named ergou:" << endl;
		iter_ergou->print();
		// modify ergou
		student ergou = *iter_ergou;
		ergou.id = 6;            // will be success. becasuse id 6 not in the table. otherwise failure
		ergou.name = "ergou_v2";
		ergou.score = 91;
		ergou.remark = "hello ergou";
		bool isSuc = find_name.replace(iter_ergou, ergou);
	}
	// 
	cout << "sort by student id after replace ergou:" << endl;
	student_table::index<_id>::type::iterator iter_id_v2 = sort_id.begin();
	for (; iter_id_v2 != sort_id.end(); iter_id_v2++) {
		iter_id_v2->print();
	}
	cout << "\\n" << endl;
 
	system("pause");
}

输出结果：

参考：

1. boost::multi_index多索引容器-使用说明