What are the introductory knowledge points of redis?

Redis is a high-performance key-value database. The emergence of redis has largely compensated for the shortcomings of keyvalue storage such as memcached, and can play a very good supplementary role to relational databases in some situations.

1. Install Redis

Redis configuration file:/etc/redis.conf

Redis main program:/usr/bin/ redis-server

Client tool:/usr/bin/redis-cli

Default listening port: 6379

Data directory:/var/lib/redis

Service script:/usr/lib/systemd/system/redis.service

yum install redis                  # 基于CentOS7的epel源

2. Connect to Redis

The client command tool of Redis is redis-cli, which connects to the local one by default Redis service.

If you need remote connection, use redis-cli -h HOST -p PORT -a PASSWD

[root@cache1 ~]# redis-cli127.0.0.1:6379> ping                            # 使用ping命令测试与服务的连接性PONG                                            # 服务端回复pong则说明网络连接没有问题

3. Redis data type

String (string)

String is the most basic type of redis. You can understand it as the same type as Memcached. One key corresponds to one value.

The string type is binary safe. This means that the redis string can contain any data. For example, jpg images or serialized objects.

The string type is the most basic data type of Redis, and a key can store up to 512MB.

Hash (Hash)

Redis hash is a collection of key-value (key=>value) pairs.

Redis hash is a mapping table of string type fields and values. Hash is particularly suitable for storing objects.

List (List)

Redis list is a simple list of strings, sorted in insertion order. You can add an element to the head (left) or tail (right) of the list.

Set (set)

Redis’ Set is an unordered collection of string type.

Sets are implemented through hash tables, so the complexity of adding, deleting, and searching is O(1).

zset (sorted set: ordered set)

Redis zset, like set, is also a collection of string type elements, and duplicate members are not allowed.

The difference is that each element is associated with a double type score. Redis uses scores to sort the members of the collection from small to large.

The members of zset are unique, but the scores can be repeated.

4. Get help

help @  + 双击tab                        # 双击tab会出现各种子命令的帮助help @string                            # 字符串相关的配置help @list                              # 列表相关的配置；列表类似于数组help @sethelp @hash......

5. List-related commands

The other data types are relatively simple, and you can get the usage of the commands through help. The easiest way is Baidu. In order to better understand some operations, we will explain the most commonly used commands related to List separately, because it may not be easy to understand just by looking at the help

Example:

127.0.0.1:6379> LPUSH stu aubin                 # LPUSH，向列表左侧添加元素，列表不存在自动创建(integer) 1
127.0.0.1:6379> RPUSH stu 22                    # RPUSH，向列表右侧添加元素，列表不存在则自动创建(integer) 2
127.0.0.1:6379> RPUSHX  stu nan                 # RPUSHX，如果列表存在则右侧添加元素(integer) 3
127.0.0.1:6379> LPUSHX  stu linux               # LPUSHX，如果列表存在则左侧添加元素(integer) 4
127.0.0.1:6379> LRANGE stu 0 10                 # LRANGE，显示名为stu的列表的0-10个值1) "aubin"2) "22"3) "nan"4) "linux"LPOP stu                                # 左弹，删除名为stu列表中的第一个元素RPOP stu                                # 右弹，删除名为stu列表中的最后一个元素LREM stu  3  aubin                      # 从头到尾删除3个值为aubin的元素LREM stu  -3  aubin                     # 从尾到头删除3个值为aubin的元素LREM stu  0  aubin                      # 删除所有值为aubin的元素

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