一、谷歌布隆过滤器

项目地址：https://gitee.com/quancong/redis.git
BloomFilter项目

需求：判断是否是已注册过的用户

1、引入布隆过滤器pom依赖

    <!-- 谷歌布隆过滤器-->
     <dependency>
         <groupId>com.google.guava</groupId>
         <artifactId>guava</artifactId>
         <version>21.0</version>
    </dependency>

2、数据库中表数据

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` int NOT NULL AUTO_INCREMENT COMMENT '主键',
  `username` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL DEFAULT '' COMMENT '用户名',
  `password` varchar(20) NOT NULL DEFAULT '' COMMENT '用户创建时间',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

BEGIN;
INSERT INTO `user` VALUES (1, '张三', '2020-07-31 17:08:42');
INSERT INTO `user` VALUES (2, '李四', '2020-07-31 07:10:14');
INSERT INTO `user` VALUES (3, '王五', '2020-07-31 20:30:09');
COMMIT;

SET FOREIGN_KEY_CHECKS = 1;

3、启动springboot项目时将用户id添加到布隆过滤器中来

/**
 * 启动时初始化布隆过滤器
 */
@Service
public class BloomFilterService implements ApplicationRunner {

    @Autowired
    private UserDao userDao;

    private BloomFilter<Integer> bf;

    /**
     * 启动时将数据库中用户id加载到布隆过滤器中来
     * @param args
     * @throws Exception
     */
    @Override
    public void run(ApplicationArguments args) throws Exception {
        List<Integer> userIdList = userDao.findAllUserId();
        if (CollectionUtils.isEmpty(userIdList)) return;
        //创建布隆过滤器 误判率默认为3%
        bf = BloomFilter.create(Funnels.integerFunnel(),userIdList.size());
        for (Integer userId : userIdList) {
            bf.put(userId);
        }
    }

    /***
     * 判断id可能存在于布隆过滤器里面
     * @param id
     * @return
     */
    public boolean userIdExists(int id){
        return bf.mightContain(id);
    }
}

这里同时还有一个判断用户id可能存在的方法

4、编写controller测试一下

@RestController
public class UserController {

    @Autowired
    private BloomFilterService bloomFilterService;

    @RequestMapping("/bloom/idExists")
    public boolean ifExists(int id){
        return bloomFilterService.userIdExists(id);
    }
}

浏览器输入http://localhost:8080/bloom/idExists?id=1，即一个已存在的用户id

输入一个存在的用户id返回true

输入一个不存在的用户id返回false

二、redis原生setbit命令实现

因篇幅过长，可参见我的另一篇博客。

https://blog.csdn.net/qq_41963899/article/details/108911244

三、使用redis布隆过滤器插件实现

1、安装布隆过滤器

git clone git://github.com/RedisLabsModules/rebloom
cd rebloom
make

2、有一个redisbloom.so文件，复制路径，假如为path，在redis.conf中指定该模块

loadmodule /path/rebloom.so

3、重启redis

redis-server  ./redis.conf

4、测试

redis-cli bf.add myBloom redis1 # 向myBloom布隆过滤器添加redis1键
redis-cli bf.add myBloom redis2
redis-cli # 进入redis客户端

判断yBloom布隆过滤器是否存在redis1、redis2、redis3这些键

bf.exists myBloom redis1
bf.exists myBloom redis2
bf.exists myBloom redis3

5、springboot整合redis布隆过滤器

项目源码：https://gitee.com/quancong/redis.git

@Service
public class RedisBloomFilter {

    @Autowired
    private RedisTemplate redisTemplate;
    
    public Boolean bloomFilterAdd(String filterName,int value){
        DefaultRedisScript<Boolean> bloomAdd = new DefaultRedisScript<>();
        bloomAdd.setScriptSource(new ResourceScriptSource(new ClassPathResource("bloomFilterAdd.lua")));
        bloomAdd.setResultType(Boolean.class);
        List<Object> keyList= new ArrayList<>();
        keyList.add(filterName);
        keyList.add(value+"");
        Boolean result = (Boolean) redisTemplate.execute(bloomAdd,keyList);
        return result;
    }
    
    public Boolean bloomFilterExists(String filterName,int value){
        DefaultRedisScript<Boolean> bloomExists= new DefaultRedisScript<>();
        bloomExists.setScriptSource(new ResourceScriptSource(new ClassPathResource("bloomFilterExist.lua")));
        bloomExists.setResultType(Boolean.class);
        List<Object> keyList= new ArrayList<>();
        keyList.add(filterName);
        keyList.add(value+"");
        Boolean result = (Boolean) redisTemplate.execute(bloomExists,keyList);
        return result;
    }
}

测试一下：

@RestController
public class RedisController {

    @Autowired
    private RedisBloomFilter redisBloomFilter;

    @RequestMapping("/bloom/redisIdExists")
    public boolean redisidExists(int id){
        return redisBloomFilter.bloomFilterExists("myBloom",id);
    }

    @RequestMapping("/bloom/redisIdAdd")
    public boolean redisidAdd(int id){
        return redisBloomFilter.bloomFilterAdd("myBloom",id);
    }

}

先往布隆过滤器中添加两条数据

http://localhost:8080/bloom/redisIdAdd?id=1

再测试一下redis布隆过滤器不存在的数据

http://localhost:8080/bloom/redisIdExists?id=3

成功！