Redis高级数据类型(HyperLogLog、Bitmap)

HyperLogLog

• 采用一种基数算法，用于完成独立总数的统计。
• 占据空间小，无论统计多少个数据，只占12k的内存
• 不精确的统计算法，标准误差为0.81%

当数据量较大，但是不要求精确值的时候可以使用HyperLogLog

使用

    //统计20万重复数字的独立总数(就是去重之后的总数)
    @Test
    public void testHyperLogLog(){
        String redisKey="test:hll:01";
        for(int i=1;i<=100000;i++){
            redisTemplate.opsForHyperLogLog().add(redisKey,i);
        }
        for(int i=1;i<=100000;i++){
            int r=(int)(Math.random()*100000+1);
            redisTemplate.opsForHyperLogLog().add(redisKey,r);
        }
        long size=redisTemplate.opsForHyperLogLog().size(redisKey);
        System.out.println(size);

    }
    //合并三组数据,并统计合并后的独立总数
    @Test
    public void  testHyperLogLogUnion(){
        String redisKey2="test:hll:02";
        String redisKey3="test:hll:03";
        String redisKey4="test:hll:04";
        for(int i=1;i<=10000;i++){
            redisTemplate.opsForHyperLogLog().add(redisKey2,i);
        }
        for(int i=5001;i<=15000;i++){
            redisTemplate.opsForHyperLogLog().add(redisKey3,i);
        }
        for(int i=10000;i<=20000;i++){
            redisTemplate.opsForHyperLogLog().add(redisKey4,i);
        }
        String union="test:hll:05";
        redisTemplate.opsForHyperLogLog().union(union,redisKey2,redisKey3,redisKey4);
        long size=redisTemplate.opsForHyperLogLog().size(union);
        System.out.println(size);
    }

Bitmap

• 不是一种独立的数据结构,实际上就是字符串(特殊的字符串)
• 支持按位存取数据(每一位只能存储0和1)，可以将其看做成byte数组
• 适合存储索大量的连续的数据的布尔值(能够统计精确地值)

可以用于统计网站的签到,用户每天登陆了没有

使用

    //统计一组数据的布尔值
    @Test
    public void testBitmap(){
        String redisKey="test:bm:01";
        //存储(没有存储的位置默认是false,所以只需要存储true即可)
        redisTemplate.opsForValue().setBit(redisKey,1,true);
        redisTemplate.opsForValue().setBit(redisKey,4,true);
        redisTemplate.opsForValue().setBit(redisKey,7,true);
        //按位查询
        System.out.println(redisTemplate.opsForValue().getBit(redisKey, 0));
        System.out.println(redisTemplate.opsForValue().getBit(redisKey, 1));
        System.out.println(redisTemplate.opsForValue().getBit(redisKey, 2));
        //统计true个数
        Object execute = redisTemplate.execute(new RedisCallback() {
            @Override
            public Object doInRedis(RedisConnection connection) throws DataAccessException {
                return connection.bitCount(redisKey.getBytes());
            }
        });
        System.out.println(execute);
    }

//统计三组数据的布尔值,并对三组数据进行OR运算
    @Test
    public void testBitmap2(){
        String redisKey2="test:bm:02";
        String redisKey3="test:bm:03";
        String redisKey4="test:bm:04";
        redisTemplate.opsForValue().setBit(redisKey2,0,true);
        redisTemplate.opsForValue().setBit(redisKey2,1,true);
        redisTemplate.opsForValue().setBit(redisKey2,2,true);

        redisTemplate.opsForValue().setBit(redisKey2,2,true);
        redisTemplate.opsForValue().setBit(redisKey2,3,true);
        redisTemplate.opsForValue().setBit(redisKey2,4,true);

        redisTemplate.opsForValue().setBit(redisKey2,4,true);
        redisTemplate.opsForValue().setBit(redisKey2,5,true);
        redisTemplate.opsForValue().setBit(redisKey2,6,true);
        String redisKey="test:bm:or";
        Object obj=redisTemplate.execute(new RedisCallback() {
            @Override
            public Object doInRedis(RedisConnection connection) throws DataAccessException {
                connection.bitOp(RedisStringCommands.BitOperation.OR, redisKey.getBytes(), redisKey2.getBytes(), redisKey3.getBytes(), redisKey4.getBytes());
                return connection.bitCount(redisKey.getBytes());
            }
        });
        System.out.println(obj);
        System.out.println(redisTemplate.opsForValue().getBit(redisKey, 0));
        System.out.println(redisTemplate.opsForValue().getBit(redisKey, 1));
        System.out.println(redisTemplate.opsForValue().getBit(redisKey, 2));
        System.out.println(redisTemplate.opsForValue().getBit(redisKey, 3));
        System.out.println(redisTemplate.opsForValue().getBit(redisKey, 4));
        System.out.println(redisTemplate.opsForValue().getBit(redisKey, 5));
        System.out.println(redisTemplate.opsForValue().getBit(redisKey, 6));
    }