redis： sorted set数据类型与操作

redis支持有序集合，即sorted sets数据类型。基本格式为：

key --> member -- score

| --> member -- score

sorted set类型的实现采用了两个数据结构：hash table 和 skip list(跳跃表)，其中hash table是具体使用redis中的dict来实现的，主要是为了保证查询效率为O(1) ，而skip list(跳跃表)主要是保证元素有序并能够保证INSERT和REMOVE操作是O(logn)的复杂度。

sorted set的基本操作详见：http://redis.readthedocs.org/en/2.4/sorted_set.html

利用redis c++接口，验证zset的基本操作：

#include "redisclient.h"

#include "tests/functions.h"

#include <iostream>

#include <boost/date_time.hpp>

#define OUT(x) std::cout<<#x<<" = "<<x<<std::endl;

boost::shared_ptr<redis::client> init_non_cluster_client();

void output_set(redis::client::string_set & sset);
void output_sort_set(redis::client & c, std::string & key);

void test_sorted_set(redis::client & c);

int main(int argv, char* argc[])
{
boost::shared_ptr<redis::client> shared_c;

shared_c = init_non_cluster_client();

redis::client& c = *shared_c;

test_sorted_set(c);

return 0;
}

void test_sorted_set(redis::client & c)
{
test("test sorted set:");

std::string key = "page_rank";
test("zadd");
{
c.zadd(key, 10, "taobao.com");
c.zadd(key, 9, "tmall.com");
c.zadd(key, make_pair("tmall.com", 11.1) );
output_sort_set(c, key);
}

test("zrem");
{
c.zrem(key, "taobao.com");
output_sort_set(c, key);
}

test("zcount");
{
OUT(c.zcount(key, 0, 5));
c.zadd(key, 3.6, "etao.com");
OUT(c.zcount(key, 0, 5));
}

test("zincrby");
{
c.zincrby(key,"etao.com", 3);
c.zincrby(key,"koubei.com", 5);
output_sort_set(c, key);
}

test("zrevrange");
{
redis::client::string_vector out;
c.zrevrange(key, 0, -1, out);
for(size_t i=0; i<out.size(); ++i) {
OUT(out[i]);
}
}

test("zrangebyscore");
{
redis::client::string_score_vector out;
c.zrangebyscore(key, 0, 20, out, 0, 2);
for(size_t i=0; i<out.size(); i++) {
OUT(out[i].first);
OUT(out[i].second);
}
}

test("zrank & zrevrank");
{
OUT(c.zrank(key, "etao.com"));
OUT(c.zrevrank(key, "etao.com"));
}

test("zremrangebyrank & zremrangebyscore");
{
c.zremrangebyrank(key, 0, 0);
c.zremrangebyscore(key, 0, 10);
output_sort_set(c, key);
}

test("zinterstore & zunionstore");
{
c.zadd("website", 10, "taobao.com");
c.zadd("website", 8, "google.com");
c.zadd("website", 0, "baidu.com");
c.zadd("website", 7, "tmall.com");

redis::client::string_vector keys;
keys.push_back(key);
keys.push_back("website");

std::string sinter("inter");
std::string sunion("union");
c.zinterstore(sinter, keys);
c.zunionstore(sunion, keys);

std::cout<<"inter :"<<std::endl;
output_sort_set(c, sinter);
std::cout<<"union :"<<std::endl;
output_sort_set(c, sunion);
}
}

void output_sort_set(redis::client & c, std::string & key)
{
OUT( c.zcard(key) );
redis::client::string_vector out;
c.zrange(key, 0, -1, out);
for(size_t i=0; i<out.size(); ++i) {
OUT(out[i]);
OUT( c.zscore(key, out[i]) );
}
}

PS：

redis c++接口在实现zset操作时，有两个小bug:

1. void recv_int_ok_reply_(int socket)

原来实现，当recv_int_reply_(socket) != 1时，就认为有错误，从而抛出异常：throw protocol_error("expecting int reply of 1");

但实际上，如zadd操作：

如果某个member已经是有序集的成员，那么更新这个member的score值，并通过重新插入这个member元素，来保证该member在正确的位置上，并返回0；
add成功返回1；如果key不存在，则创建一个空的有序集并执行zadd操作；当key存在但不是有序集类型时，返回一个错误。

修改：

void recv_int_ok_reply_(int socket)
{
if (recv_int_reply_(socket) < 0)
throw protocol_error("expecting int reply of <0");
}

2. void zrangebyscore(const string_type & key, double min, double max, string_score_vector & out, int_type offset = 0, int_type max_count = -1, int range_modification = 0)

调用，zrangebyscore_base(true, key, min, max, res, offset, max_count, range_modification);

第一个参数值等于true表明，需要返回score值。但是，zrangebyscore_base在实现时并未考虑这一参数。

修改：在zrangebyscore_base函数实现时，加上

if(withscores) {
m << "WITHSCORES";
}