redis:set数据类型与操作

set是集合。我们可以向一个集合中“插入”，“删除”元素，也可以计算两个集合的“交集”，“并集”，及“作差”。如：

假设有集合A，B。

其中，A={1,2,3,4,5},B={4,5,6,7,8}。

那么，

交集：inter（A，B）= {4,5}

并集：union（A， B）= {1,2,3,4,5,6,7,8}

差集：diff（A，B）= {1,2,3}，即属于集合A，但不属于集合B的元素

set的是通过hash table实现的，所以添加、删除和查找的复杂度都是O(1)。hash table会随着添加或者删除自动的调整大小。需要注意的是调整hash table大小时候需要同步(获取写锁)会阻塞其他读写操作，可能不久后就会改用跳表(skip list)来实现，跳表已经在sorted set中使用了。（引自：http://hb.qq.com/a/20111001/000022.htm）

关于set数据类型的操作详见：http://redis.readthedocs.org/en/2.4/set.html

下面结合redis c++接口，了解一下这些基本操作。

#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 test_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_set(c);

return 0;
}

void test_set(redis::client & c)
{
test("test redis set type.");

test("sadd");
{
std::vector<std::string> vals;
for(size_t i=0; i<10; ++i) {
char ch = (char)('A'+i);
std::string tmp ="";
tmp += ch;
vals.push_back(tmp);
}
std::vector<std::string>::iterator it;
c.sadd("set_a", vals.begin(), vals.end());
}

test("smembers");
{
redis::client::string_set out;
OUT(c.smembers("set_a", out));
output_set( out );
}

test("srem");
{
c.srem("set_a", "A");
redis::client::string_set out;
OUT(c.smembers("set_a", out));
output_set( out );
}

test("sismember");
{
OUT( c.sismember("set_a", "A") );
OUT( c.sismember("set_a", "B") );
}

test("scard");
{
OUT( c.scard("set_a") );
}

test("smove");
{
c.smove("set_a", "set_b", "B");
redis::client::string_set out;
OUT(c.smembers("set_a", out));
output_set(out);

out.clear();
OUT(c.smembers("set_b", out));
output_set( out );
}

test("spop");
{
OUT( c.scard("set_a") );
OUT( c.spop("set_a") );
OUT( c.scard("set_a") );
}

test("srandmember");
{
OUT( c.srandmember("set_a") );
}

test("sinter");
{
c.sadd("set_b", "C");
c.sadd("set_b", "F");
redis::client::string_vector keys;
keys.push_back("set_a");
keys.push_back("set_b");
redis::client::string_set out;
c.smembers("set_a", out);
std::cout<<"set a:  *******************"<<std::endl;
output_set(out);
out.clear();
c.smembers("set_b", out);
std::cout<<"set b:  *******************"<<std::endl;
output_set(out);
c.sinter(keys, out);
output_set(out);
}

test("sinterstore");
{
redis::client::string_vector keys;
redis::client::string_set out;
keys.push_back("set_a");
keys.push_back("set_b");
c.sinterstore("set_c", keys);
c.smembers("set_c", out);
output_set(out);
}

test("sunion & sunionstore");
{
redis::client::string_vector keys;
redis::client::string_set out;
keys.push_back("set_a");
keys.push_back("set_b");
c.sunion(keys, out);
output_set(out);
out.clear();
c.sunionstore("set_d", keys);
c.smembers("set_d", out);
std::cout<<"set d: ****************"<<std::endl;
output_set(out);
}

test("sdiff * sdiffstore");
{
redis::client::string_vector keys;
redis::client::string_set out;
keys.push_back("set_a");
keys.push_back("set_b");
c.sdiff(keys, out);
output_set(out);
out.clear();
c.sdiffstore("set_e", keys);
c.smembers("set_e", out);
std::cout<<"set e: ****************"<<std::endl;
output_set(out);
}
}

void output_set(redis::client::string_set & sset)
{
size_t size = sset.size();
OUT(size);
redis::client::string_set::iterator it;
for(it=sset.begin(); it!=sset.end(); ++it) {
OUT(*it);
}
}