redis常见的使用案例

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zzz1220 5月 30, 2021
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redis除了缓存，还有很多的使用方式，互联网项目的很多功能都是通过redis实现的，今天简单介绍一些。

简单回顾下redis是什么

Redis是一个使用ANSI C编写的开源、支持网络、基于内存、分布式、可选持久性的键值对存储数据库。从2015年6月开始，Redis的开发由Redis Labs赞助，而2013年5月至2015年6月期间，其开发由Pivotal赞助。在2013年5月之前，其开发由VMware赞助。根据月度排行网站DB-Engines.com的数据，Redis是最流行的键值对存储数据库。

redis的特点

  1. 高性能
    性能极高 – Redis能读的速度是110000次/s,写的速度是81000次/s 。
  2. 和原生语言无缝的数据结构
    Redis支持二进制案例的 Strings, Lists, Hashes, Sets 及 Ordered Sets 数据类型操作。
  3. 丰富的特性
    Redis还支持 publish/subscribe, 通知, key 过期等等特性。
  4. 支持持久化
    Redis支持数据的持久化，可以将内存中的数据保存在磁盘中，重启的时候可以再次加载进行使用。
  5. 分布式
    Redis支持数据的备份，即master-slave模式的数据备份。
  6. 高可用
    Redis Sentinel 一个分布式架构，监控各个机器的状态及时作出调整，重新选取主节点。

五种数据类型和常见用法

1. string

string在redis里是通过字符数组实现的。你可以理解成与 Memcached 一模一样的类型，一个 key 对应一个 value。value其实不仅是String，也可以是数字。string 类型是二进制安全的。意思是 redis 的 string 可以包含任何数据。比如jpg图片或者序列化的对象。string 类型是 Redis 最基本的数据类型，string 类型的值最大能存储 512MB。

常见的场景

  1. json字符串储存缓存
  2. string也可以是一个数字，所以也可以作为计数器，使用INCR命令
  3. redis也支持二进制，所以可以当作一个bitmap,把固定长度的bit位储存数据。
  4. 布隆过滤器，一个很长的二进制向量，作为超大的包含关系的查询。详细点击这里
  5. 分布式锁，比较复杂，可以看下这里。

常用命令：


  APPEND key value
  summary: Append a value to a key
  since: 2.0.0

  BITCOUNT key [start end]
  summary: Count set bits in a string
  since: 2.6.0

  BITFIELD key [GET type offset] [SET type offset value] [INCRBY type offset increment] [OVERFLOW WRAP|SAT|FAIL]
  summary: Perform arbitrary bitfield integer operations on strings
  since: 3.2.0

  BITOP operation destkey key [key ...]
  summary: Perform bitwise operations between strings
  since: 2.6.0

  BITPOS key bit [start] [end]
  summary: Find first bit set or clear in a string
  since: 2.8.7

  DECR key
  summary: Decrement the integer value of a key by one
  since: 1.0.0

  DECRBY key decrement
  summary: Decrement the integer value of a key by the given number
  since: 1.0.0

  GET key
  summary: Get the value of a key
  since: 1.0.0

  GETBIT key offset
  summary: Returns the bit value at offset in the string value stored at key
  since: 2.2.0

  GETRANGE key start end
  summary: Get a substring of the string stored at a key
  since: 2.4.0

  GETSET key value
  summary: Set the string value of a key and return its old value
  since: 1.0.0

  INCR key
  summary: Increment the integer value of a key by one
  since: 1.0.0

  INCRBY key increment
  summary: Increment the integer value of a key by the given amount
  since: 1.0.0

  INCRBYFLOAT key increment
  summary: Increment the float value of a key by the given amount
  since: 2.6.0

  MGET key [key ...]
  summary: Get the values of all the given keys
  since: 1.0.0

  MSET key value [key value ...]
  summary: Set multiple keys to multiple values
  since: 1.0.1

  MSETNX key value [key value ...]
  summary: Set multiple keys to multiple values, only if none of the keys exist
  since: 1.0.1

  PSETEX key milliseconds value
  summary: Set the value and expiration in milliseconds of a key
  since: 2.6.0

  SET key value [EX seconds] [PX milliseconds] [NX|XX]
  summary: Set the string value of a key
  since: 1.0.0

  SETBIT key offset value
  summary: Sets or clears the bit at offset in the string value stored at key
  since: 2.2.0

  SETEX key seconds value
  summary: Set the value and expiration of a key
  since: 2.0.0

  SETNX key value
  summary: Set the value of a key, only if the key does not exist
  since: 1.0.0

  SETRANGE key offset value
  summary: Overwrite part of a string at key starting at the specified offset
  since: 2.2.0

  STRLEN key
  summary: Get the length of the value stored in a key
  since: 2.2.0

2. hash

Hash 是一个键值(key => value)对集合。Redis hash 是一个 string 类型的 field 和 value 的映射表，hash 特别适合用于存储对象。比如储存用户信息。用户id作为key，姓名，年龄，生日等信息可以维护序列化的对象。

使用场景

  1. 存储对象类数据，因此可以存一些结构化的数据，比如购物车，用户基本信息。

  HDEL key field [field ...]
  summary: Delete one or more hash fields
  since: 2.0.0

  HEXISTS key field
  summary: Determine if a hash field exists
  since: 2.0.0

  HGET key field
  summary: Get the value of a hash field
  since: 2.0.0

  HGETALL key
  summary: Get all the fields and values in a hash
  since: 2.0.0

  HINCRBY key field increment
  summary: Increment the integer value of a hash field by the given number
  since: 2.0.0

  HINCRBYFLOAT key field increment
  summary: Increment the float value of a hash field by the given amount
  since: 2.6.0

  HKEYS key
  summary: Get all the fields in a hash
  since: 2.0.0

  HLEN key
  summary: Get the number of fields in a hash
  since: 2.0.0

  HMGET key field [field ...]
  summary: Get the values of all the given hash fields
  since: 2.0.0

  HMSET key field value [field value ...]
  summary: Set multiple hash fields to multiple values
  since: 2.0.0

  HSCAN key cursor [MATCH pattern] [COUNT count]
  summary: Incrementally iterate hash fields and associated values
  since: 2.8.0

  HSET key field value
  summary: Set the string value of a hash field
  since: 2.0.0

  HSETNX key field value
  summary: Set the value of a hash field, only if the field does not exist
  since: 2.0.0

  HSTRLEN key field
  summary: Get the length of the value of a hash field
  since: 3.2.0

  HVALS key
  summary: Get all the values in a hash
  since: 2.0.0

3. list

list 列表是简单的字符串列表，按照插入顺序排序。你可以添加一个元素到列表的头部（左边）或者尾部（右边）。
可以作为一个简单的消息队列。

使用场景

  1. 简易消息队列，右(左)边进左(右)边出，用来消费队列里的信息。但是ack机制麻烦，复杂场景还是使用专业的mq。
  2. 作为栈使用，支持右(左)边进右(左)边出。
  3. 用于储存线性数据，比如某个人的关注列表。文章点赞的人的id。

  BLPOP key [key ...] timeout
  summary: Remove and get the first element in a list, or block until one is available
  since: 2.0.0

  BRPOP key [key ...] timeout
  summary: Remove and get the last element in a list, or block until one is available
  since: 2.0.0

  BRPOPLPUSH source destination timeout
  summary: Pop a value from a list, push it to another list and return it; or block until one is available
  since: 2.2.0

  LINDEX key index
  summary: Get an element from a list by its index
  since: 1.0.0

  LINSERT key BEFORE|AFTER pivot value
  summary: Insert an element before or after another element in a list
  since: 2.2.0

  LLEN key
  summary: Get the length of a list
  since: 1.0.0

  LPOP key
  summary: Remove and get the first element in a list
  since: 1.0.0

  LPUSH key value [value ...]
  summary: Prepend one or multiple values to a list
  since: 1.0.0

  LPUSHX key value
  summary: Prepend a value to a list, only if the list exists
  since: 2.2.0

  LRANGE key start stop
  summary: Get a range of elements from a list
  since: 1.0.0

  LREM key count value
  summary: Remove elements from a list
  since: 1.0.0

  LSET key index value
  summary: Set the value of an element in a list by its index
  since: 1.0.0

  LTRIM key start stop
  summary: Trim a list to the specified range
  since: 1.0.0

  RPOP key
  summary: Remove and get the last element in a list
  since: 1.0.0

  RPOPLPUSH source destination
  summary: Remove the last element in a list, prepend it to another list and return it
  since: 1.2.0

  RPUSH key value [value ...]
  summary: Append one or multiple values to a list
  since: 1.0.0

  RPUSHX key value
  summary: Append a value to a list, only if the list exists
  since: 2.2.0

4. set

set 是string类型的无序集合。集合是通过hashtable实现的，概念和数学中个的集合基本类似，可以交集，并集，差集等等，set中的元素是没有顺序的。所以添加，删除，查找的复杂度都是O(1)。

使用场景

  1. 去重，多台服务可以放在一个set里去重。
  2. redis 提供了求交集、并集、差集的操作，可以非常方便的实现如共同关注、共同喜好、二度好友等功能。

  SADD key member [member ...]
  summary: Add one or more members to a set
  since: 1.0.0

  SCARD key
  summary: Get the number of members in a set
  since: 1.0.0

  SDIFF key [key ...]
  summary: Subtract multiple sets
  since: 1.0.0

  SDIFFSTORE destination key [key ...]
  summary: Subtract multiple sets and store the resulting set in a key
  since: 1.0.0

  SINTER key [key ...]
  summary: Intersect multiple sets
  since: 1.0.0

  SINTERSTORE destination key [key ...]
  summary: Intersect multiple sets and store the resulting set in a key
  since: 1.0.0

  SISMEMBER key member
  summary: Determine if a given value is a member of a set
  since: 1.0.0

  SMEMBERS key
  summary: Get all the members in a set
  since: 1.0.0

  SMOVE source destination member
  summary: Move a member from one set to another
  since: 1.0.0

  SPOP key [count]
  summary: Remove and return one or multiple random members from a set
  since: 1.0.0

  SRANDMEMBER key [count]
  summary: Get one or multiple random members from a set
  since: 1.0.0

  SREM key member [member ...]
  summary: Remove one or more members from a set
  since: 1.0.0

  SSCAN key cursor [MATCH pattern] [COUNT count]
  summary: Incrementally iterate Set elements
  since: 2.8.0

  SUNION key [key ...]
  summary: Add multiple sets
  since: 1.0.0

  SUNIONSTORE destination key [key ...]
  summary: Add multiple sets and store the resulting set in a key
  since: 1.0.0

5. sorted_set

zset 和 set 一样也是string类型元素的集合,且不允许重复的成员。 *zadd 命令：*添加元素到集合，元素在集合中存在则更新对应score。set是有序的，根据score排序。

使用场景

  1. 因为自带排序，显示最新的项目列表 ，排行榜相关。
  2. 处理过期项目，比如处理没付款的订单。根据下单时间放进sorted_set，后台任务根据ZRANGE查最近的几条数据，如果过期再回写到数据库。

  ZADD key [NX|XX] [CH] [INCR] score member [score member ...]
  summary: Add one or more members to a sorted set, or update its score if it already exists
  since: 1.2.0

  ZCARD key
  summary: Get the number of members in a sorted set
  since: 1.2.0

  ZCOUNT key min max
  summary: Count the members in a sorted set with scores within the given values
  since: 2.0.0

  ZINCRBY key increment member
  summary: Increment the score of a member in a sorted set
  since: 1.2.0

  ZINTERSTORE destination numkeys key [key ...] [WEIGHTS weight] [AGGREGATE SUM|MIN|MAX]
  summary: Intersect multiple sorted sets and store the resulting sorted set in a new key
  since: 2.0.0

  ZLEXCOUNT key min max
  summary: Count the number of members in a sorted set between a given lexicographical range
  since: 2.8.9

  ZRANGE key start stop [WITHSCORES]
  summary: Return a range of members in a sorted set, by index
  since: 1.2.0

  ZRANGEBYLEX key min max [LIMIT offset count]
  summary: Return a range of members in a sorted set, by lexicographical range
  since: 2.8.9

  ZRANGEBYSCORE key min max [WITHSCORES] [LIMIT offset count]
  summary: Return a range of members in a sorted set, by score
  since: 1.0.5

  ZRANK key member
  summary: Determine the index of a member in a sorted set
  since: 2.0.0

  ZREM key member [member ...]
  summary: Remove one or more members from a sorted set
  since: 1.2.0

  ZREMRANGEBYLEX key min max
  summary: Remove all members in a sorted set between the given lexicographical range
  since: 2.8.9

  ZREMRANGEBYRANK key start stop
  summary: Remove all members in a sorted set within the given indexes
  since: 2.0.0

  ZREMRANGEBYSCORE key min max
  summary: Remove all members in a sorted set within the given scores
  since: 1.2.0

  ZREVRANGE key start stop [WITHSCORES]
  summary: Return a range of members in a sorted set, by index, with scores ordered from high to low
  since: 1.2.0

  ZREVRANGEBYLEX key max min [LIMIT offset count]
  summary: Return a range of members in a sorted set, by lexicographical range, ordered from higher to lower strings.
  since: 2.8.9

  ZREVRANGEBYSCORE key max min [WITHSCORES] [LIMIT offset count]
  summary: Return a range of members in a sorted set, by score, with scores ordered from high to low
  since: 2.2.0

  ZREVRANK key member
  summary: Determine the index of a member in a sorted set, with scores ordered from high to low
  since: 2.0.0

  ZSCAN key cursor [MATCH pattern] [COUNT count]
  summary: Incrementally iterate sorted sets elements and associated scores
  since: 2.8.0

  ZSCORE key member
  summary: Get the score associated with the given member in a sorted set
  since: 1.2.0

  ZUNIONSTORE destination numkeys key [key ...] [WEIGHTS weight] [AGGREGATE SUM|MIN|MAX]
  summary: Add multiple sorted sets and store the resulting sorted set in a new key
  since: 2.0.0

其他功能

  1. Pub/Sub
    Redis的Pub/Sub非常非常简单，运行稳定并且快速。可以作为发布订阅使用。
    2.geo
    储存地理坐标数据，用来实现附近的人功能。
  2. HyperLogLog
    Redis HyperLogLog 是用来做基数统计的算法，HyperLogLog 的优点是，在输入元素的数量或者体积非常非常大时，计算基数所需的空间总是固定 的、并且是很小的。
    在 Redis 里面，每个 HyperLogLog 键只需要花费 12 KB 内存，就可以计算接近 2^64 个不同元素的基 数。这和计算基数时，元素越多耗费内存就越多的集合形成鲜明对比。