Boost Multi-Index 中的多索引查询

Question

我正在编写一个将 GenericOrder（包含数量、价格、方式和时间戳）存储为 shared_ptr 的软件。
我已阅读 Boost 文档并成功定义了一个 MultiIndexOrderContainer 使用三个索引：方式、时间戳和价格。
但我没有找到同时使用多个索引迭代特定订单的方法。

#include <memory>

#include <boost/multi_index_container.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/identity.hpp>
#include <boost/multi_index/member.hpp>

using namespace ::boost;
using namespace ::boost::multi_index;

enum class Way
{
    UNDEFINED,
    BUY,
    SELL
};

template <typename QuantityType, typename PriceType>
struct GenericOrder
{
    explicit GenericOrder(const Way way, const QuantityType& quantity, const PriceType& price, const long long& timestamp)
        : way_(way), quantity_(quantity), price_(price), timestamp_(timestamp)
    {
    }

    ~GenericOrder() = default;
    GenericOrder(const GenericOrder&) = delete;
    GenericOrder& operator=(const GenericOrder&) = delete;

    Way way_;
    QuantityType quantity_;
    PriceType price_;
    long long timestamp_ = -1;
};

// Aliases
using QuantityType = int;
using PriceType = int;
using OrderType = GenericOrder<QuantityType, PriceType>;
using PointerType = std::shared_ptr<OrderType>;

struct way {};
struct timestamp {};
struct price {};

using MultiIndexOrderContainer = multi_index_container<PointerType,
    indexed_by<
    ordered_non_unique<tag<way>, member<OrderType, decltype(OrderType::way_), &OrderType::way_ >>,
    ordered_non_unique<tag<timestamp>, member<OrderType, decltype(OrderType::timestamp_), &OrderType::timestamp_ >>,
    ordered_non_unique<tag<price>, member<OrderType, decltype(OrderType::price_), &OrderType::price_>>
    >
>;

int main()
{
    MultiIndexOrderContainer c;

    // Inserting some orders
    c.insert(std::make_shared<OrderType>(Way::BUY, 10, 15, 0));
    c.insert(std::make_shared<OrderType>(Way::BUY, 10, 14, 1));
    c.insert(std::make_shared<OrderType>(Way::BUY, 10, 13, 2));
    c.insert(std::make_shared<OrderType>(Way::SELL, 10, 16, 3));
    c.insert(std::make_shared<OrderType>(Way::SELL, 10, 17, 4));
    c.insert(std::make_shared<OrderType>(Way::SELL, 10, 18, 5));

    return 0;
}

我想迭代：

1. 关于按时间戳排序的特定价格的采购订单
2. 卖出订单中最便宜的订单价格
3. 采购订单中最昂贵的订单价格

我怎样才能做到这一点？

Answer 1

Boost.MultiIndex 不提供任何特殊机制来混合由不同索引引起的顺序：使用您建议的结构，您基本上可以查询第一个参数，然后对返回的范围进行线性扫描。

另一方面，如果您的查询始终采用 (attr1, attr2, attr3) 形式，您可以使用composite keys 加快查询速度。在您的特定情况下，您可以使用复合键 (way_,price_,timestamp_) 进行三个查询

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#include <memory>
#include <iostream>

#include <boost/multi_index_container.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/composite_key.hpp>
#include <boost/multi_index/identity.hpp>
#include <boost/multi_index/member.hpp>

using namespace ::boost;
using namespace ::boost::multi_index;

enum class Way
{
    UNDEFINED,
    BUY,
    SELL
};

template <typename QuantityType, typename PriceType>
struct GenericOrder
{
    explicit GenericOrder(const Way way, const QuantityType& quantity, const PriceType& price, const long long& timestamp)
        : way_(way), quantity_(quantity), price_(price), timestamp_(timestamp)
    {
    }

    ~GenericOrder() = default;
    GenericOrder(const GenericOrder&) = delete;
    GenericOrder& operator=(const GenericOrder&) = delete;

    Way way_;
    QuantityType quantity_;
    PriceType price_;
    long long timestamp_ = -1;
};

template <typename QuantityType, typename PriceType>
std::ostream& operator<<(std::ostream& os,const GenericOrder<QuantityType,PriceType>& o)
{
    switch(o.way_){
        case Way::UNDEFINED: os<<"UNDEFINED, ";break;
        case Way::BUY: os<<"BUY, ";break;
        case Way::SELL: os<<"SELL, ";break;
    }
    return os<<o.price_<<", "<<o.timestamp_<<"\n";
}

// Aliases
using QuantityType = int;
using PriceType = int;
using OrderType = GenericOrder<QuantityType, PriceType>;
using PointerType = std::shared_ptr<OrderType>;

struct way {};
struct timestamp {};
struct price {};

using MultiIndexOrderContainer = multi_index_container<PointerType,
    indexed_by<
        ordered_non_unique<
            composite_key<
                OrderType,
                member<OrderType, decltype(OrderType::way_), &OrderType::way_ >,
                member<OrderType, decltype(OrderType::price_), &OrderType::price_>,
                member<OrderType, decltype(OrderType::timestamp_), &OrderType::timestamp_ >
            >
        >
    >
>;

int main()
{
    MultiIndexOrderContainer c;

    // Inserting some orders
    c.insert(std::make_shared<OrderType>(Way::BUY, 10, 15, 0));
    c.insert(std::make_shared<OrderType>(Way::BUY, 10, 14, 1));
    c.insert(std::make_shared<OrderType>(Way::BUY, 10, 13, 2));
    c.insert(std::make_shared<OrderType>(Way::BUY, 10, 15, 1));
    c.insert(std::make_shared<OrderType>(Way::SELL, 10, 16, 3));
    c.insert(std::make_shared<OrderType>(Way::SELL, 10, 17, 4));
    c.insert(std::make_shared<OrderType>(Way::SELL, 10, 18, 5));

    std::cout<<"Buying orders for 15, sorted by timestamp\n";
    auto p=c.equal_range(std::make_tuple(Way::BUY,15));
    while(p.first!=p.second)std::cout<<**p.first++;

    std::cout<<"Cheapest selling order\n";
    std::cout<<**c.lower_bound(Way::SELL);

    std::cout<<"Costliest buying order\n";
    std::cout<<**--c.upper_bound(Way::BUY);

return 0;
}