Redis的字典(hash)数据类型的应用场

一.字典的新增指令

1.使用"HSET"指令每次为字典数据类型的KEY新增1个字段并赋值，若字段已经存在，则会覆盖原字段存储的值

[root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021 --raw -n 10
127.0.0.1:6379[10]> KEYS *

127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HSET student id 001  # 创建一个字典类型名为student的KEY，并指定id字段的值为"001"
1
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> KEYS *
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HSET student name "Jason Yin"  # 如果KEY已经存在，我们依旧可以为字典数据类型新增一个"name"字段并指定该字段的值为"Jason Yin"
1
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> TYPE student
hash
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGET student id
001
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGET student name
Jason Yin
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HSET student name "oldboyedu"  # 如果name字段已经存在了，则此次新增会覆盖原字段存储的值哟~
0
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGET student name
oldboyedu
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> QUIT
[root@redis201.oldboyedu.com ~]# 

2.使用"HMSET"指令为字典数据类型的KEY同时新增多个字段

[root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021 --raw -n 10
127.0.0.1:6379[10]> KEYS *
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HMSET phone brand Iphone memory 4G disk 128G
OK
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> KEYS *
phone
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HMGET phone brand memory disk  # 同时获取名为phone的KEY的brand,memory,disk多个字段信息
Iphone
4G
128G
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGETALL phone  # 查看名为phone的KEY所有字段及其值。
brand
Iphone
memory
4G
disk
128G
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> QUIT
[root@redis201.oldboyedu.com ~]# 

3.使用"HSETNX"指令如果为KEY不存在的字段赋值，则会新增字段;如果为KEY已经存在的字段赋值，则赋值会失败!

[root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021 --raw -n 10
127.0.0.1:6379[10]> KEYS *
phone
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGETALL student
id
001
name
oldboyedu
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HSETNX student name "Jason Yin"  # 如果为KEY已经存在的字段赋值，则赋值会失败!
0
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGET student name
oldboyedu
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HSETNX student address "BeiJing"  # 如果为KEY不存在的字段赋值，则会新增字段
1
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGET student address
BeiJing
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGETALL student
id
001
name
oldboyedu
address
BeiJing
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> QUIT
[root@redis201.oldboyedu.com ~]# 

二.字典的查找指令

1.使用"HGETALL"指令查看字典类型KEY的所有字段名称及其值

[root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021 -n 10 --raw
127.0.0.1:6379[10]> KEYS *
phone
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGETALL phone  # 查看名为phone的KEY所有的字段名称及其存储的数据。
brand
Iphone
memory
4G
disk
128G
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> QUIT
[root@redis201.oldboyedu.com ~]# 

2.使用"HKEYS"指令查看字典类型KEY的所有字段名称

[root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021 -n 10 --raw
127.0.0.1:6379[10]> KEYS *
phone
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGETALL phone
brand
Iphone
memory
4G
disk
128G
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HKEYS phone
brand
memory
disk
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> QUIT
[root@redis201.oldboyedu.com ~]# 

3.使用"HVALS"指令查看字典类型KEY的所有字段存储的值

[root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021 -n 10 --raw
127.0.0.1:6379[10]> KEYS *
phone
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGETALL phone
brand
Iphone
memory
4G
disk
128G
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HVALS phone
Iphone
4G
128G
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> QUIT
[root@redis201.oldboyedu.com ~]# 

4.使用"HMGET"指令查看字典类型KEY的多个字段

[root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021 -n 10 --raw
127.0.0.1:6379[10]> KEYS *
phone
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGETALL phone
brand
Iphone
memory
4G
disk
128G
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HMGET phone brand disk
Iphone
128G
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> QUIT
[root@redis201.oldboyedu.com ~]# 

5.使用"HEXISTS"指令查看字典类型KEY的是否有某个字段，若存在指定的字段则返回1，若不存在指定的字段则返回0

[root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021 -n 10 --raw
127.0.0.1:6379[10]> KEYS *
phone
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGETALL phone
brand
Iphone
memory
4G
disk
128G
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HEXISTS phone brand  # 我们的phone中是存在brand字段的，因此返回值为1
1
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HEXISTS phone memory
1
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HEXISTS phone price  # 我们的phone中是不存在price字段的，因此返回值为0
0
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> QUIT
[root@redis201.oldboyedu.com ~]# 

6.使用"HLEN"指令查看某个KEY的字段数量

[root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021 -n 10 --raw
127.0.0.1:6379[10]> KEYS *
phone
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGETALL phone
brand
Iphone
memory
4G
disk
128G
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HKEYS phone
brand
memory
disk
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HLEN phone
3
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> QUIT
[root@redis201.oldboyedu.com ~]# 

7.使用"HGET"指令查看某个字典类型KEY的brand字段存储的数据

[root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021 -n 10 --raw
127.0.0.1:6379[10]> KEYS *
phone
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGETALL phone
brand
Iphone
memory
4G
disk
128G
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGET phone brand  # 查看某个字典类型KEY的brand字段存储的数据。
Iphone
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> QUIT
[root@redis201.oldboyedu.com ~]# 

三.字典的修改指令

[root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021 -n 10 --raw
127.0.0.1:6379[10]> KEYS *
phone
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HKEYS student  # 我们发现名为student的KEY是不存在"age"字段的
id
name
address
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HINCRBY student age 1  # 如果我们给不存在的字段增加1，则会创建该字段并将字段的初始值设置为0，加1后其值为1。
1
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HKEYS student  # 注意观察，不难发现名为student的KEY多了一个age字段
id
name
address
age
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGET student age
1
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HINCRBY student age 18
19
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HGET student age
19
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> QUIT
[root@redis201.oldboyedu.com ~]# 

四.字典的删除指令

1.使用"HDEL"指令删除指定KEY存在的一个或者多个字段

[root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021 -n 10 --raw
127.0.0.1:6379[10]> KEYS *
phone
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HKEYS student
id
name
address
age
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HDEL student address age  # 我们可以删除某个KEY的一个或者多个字段。
2
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> HKEYS student
id
name
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> QUIT
[root@redis201.oldboyedu.com ~]# 

2.使用"DEL"指令删除指定KEY

[root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021 -n 10 --raw
127.0.0.1:6379[10]> KEYS *
phone
student
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> DEL student
1
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> KEYS *
phone
127.0.0.1:6379[10]> 
127.0.0.1:6379[10]> QUIT
[root@redis201.oldboyedu.com ~]# 

五.字典的应用场景

1.手工方式模拟MySQL的热点数据灌入到Redis的hash数据类型进行缓存，手工导入数据并不是特别安全，生产环境中建议编写代码来实现，这样逻辑更为严谨！(本案例只是导入3000条数据就有导入数据丢失的现象!)

    (1)自行导入MySQL官方的测试数据库(world)
        [root@redis201.oldboyedu.com ~]# mysql
        Welcome to the MySQL monitor.  Commands end with ; or \g.
        Your MySQL connection id is 5
        Server version: 5.7.31 MySQL Community Server (GPL)

        Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

        Oracle is a registered trademark of Oracle Corporation and/or its
        affiliates. Other names may be trademarks of their respective
        owners.

        Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

        mysql> 
        mysql> SHOW DATABASES;
        +--------------------+
        | Database           |
        +--------------------+
        | information_schema |
        | mysql              |
        | performance_schema |
        | sys                |
        | world              |
        +--------------------+
        5 rows in set (0.00 sec)

        mysql> 
        mysql> SHOW TABLES FROM world;
        +-----------------+
        | Tables_in_world |
        +-----------------+
        | city            |
        | country         |
        | countrylanguage |
        +-----------------+
        3 rows in set (0.00 sec)

        mysql> 
        mysql> SELECT * FROM world.city LIMIT 10;  # 查看MySQL的数据，先不要看下面的SQL语句，请将其转换为Redis的语法来存储数据。
        +----+----------------+-------------+---------------+------------+
        | ID | Name           | CountryCode | District      | Population |
        +----+----------------+-------------+---------------+------------+
        |  1 | Kabul          | AFG         | Kabol         |    1780000 |
        |  2 | Qandahar       | AFG         | Qandahar      |     237500 |
        |  3 | Herat          | AFG         | Herat         |     186800 |
        |  4 | Mazar-e-Sharif | AFG         | Balkh         |     127800 |
        |  5 | Amsterdam      | NLD         | Noord-Holland |     731200 |
        |  6 | Rotterdam      | NLD         | Zuid-Holland  |     593321 |
        |  7 | Haag           | NLD         | Zuid-Holland  |     440900 |
        |  8 | Utrecht        | NLD         | Utrecht       |     234323 |
        |  9 | Eindhoven      | NLD         | Noord-Brabant |     201843 |
        | 10 | Tilburg        | NLD         | Noord-Brabant |     193238 |
        +----+----------------+-------------+---------------+------------+
        10 rows in set (0.00 sec)

        mysql> 
        mysql> SELECT
            ->     CONCAT("HMSET city_",ID," id ",ID," Name ",Name," CountryCode ",CountryCode," District ",District," Population ",Population)
            -> FROM
            ->     world.city
            -> LIMIT
            ->     10;
        +------------------------------------------------------------------------------------------------------------------------------+
        | CONCAT("HMSET city_",ID," id ",ID," Name ",Name," CountryCode ",CountryCode," District ",District," Population ",Population) |
        +------------------------------------------------------------------------------------------------------------------------------+
        | HMSET city_1 id 1 Name Kabul CountryCode AFG District Kabol Population 1780000                                               |
        | HMSET city_2 id 2 Name Qandahar CountryCode AFG District Qandahar Population 237500                                          |
        | HMSET city_3 id 3 Name Herat CountryCode AFG District Herat Population 186800                                                |
        | HMSET city_4 id 4 Name Mazar-e-Sharif CountryCode AFG District Balkh Population 127800                                       |
        | HMSET city_5 id 5 Name Amsterdam CountryCode NLD District Noord-Holland Population 731200                                    |
        | HMSET city_6 id 6 Name Rotterdam CountryCode NLD District Zuid-Holland Population 593321                                     |
        | HMSET city_7 id 7 Name Haag CountryCode NLD District Zuid-Holland Population 440900                                          |
        | HMSET city_8 id 8 Name Utrecht CountryCode NLD District Utrecht Population 234323                                            |
        | HMSET city_9 id 9 Name Eindhoven CountryCode NLD District Noord-Brabant Population 201843                                    |
        | HMSET city_10 id 10 Name Tilburg CountryCode NLD District Noord-Brabant Population 193238                                    |
        +------------------------------------------------------------------------------------------------------------------------------+
        10 rows in set (0.01 sec)

        mysql> 

    (2)将MySQL的数据导出到文件中，但注意导出时要符合Redis数据库的HASH数据类型语法
        [root@redis201.oldboyedu.com ~]# mysql
        Welcome to the MySQL monitor.  Commands end with ; or \g.
        Your MySQL connection id is 3
        Server version: 5.7.31-log MySQL Community Server (GPL)

        Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

        Oracle is a registered trademark of Oracle Corporation and/or its
        affiliates. Other names may be trademarks of their respective
        owners.

        Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

        mysql>
        mysql>SELECT
            ->     CONCAT("HMSET city_",ID," id ",ID," Name ",Name," CountryCode ",CountryCode," District ",District," Population ",Population)
            -> FROM
            ->     world.city
            -> LIMIT
            ->     3000
            -> INTO 
            ->     OUTFILE "/tmp/redis.sql";
        Query OK, 3000 rows affected (0.01 sec)

        mysql>
        mysql>QUIT
        Bye
        [root@redis201.oldboyedu.com ~]# 
        [root@redis201.oldboyedu.com ~]# ll /tmp/redis.sql 
        -rw-rw-rw- 1 mysql mysql 273109 2月  28 17:58 /tmp/redis.sql
        [root@redis201.oldboyedu.com ~]# 
        [root@redis201.oldboyedu.com ~]# wc -l /tmp/redis.sql 
        3000 /tmp/redis.sql
        [root@redis201.oldboyedu.com ~]# 

    (3)将MySQL导出的语句转换为Redis中的数据
        [root@redis201.oldboyedu.com ~]# cat /tmp/redis.sql | redis-cli -a oldboyedu2021 &> /tmp/load_mysql2redis.log
        [root@redis201.oldboyedu.com ~]# 
        [root@redis201.oldboyedu.com ~]# wc -l /tmp/load_mysql2redis.log  # 发现行数大于3000，说明此次导入肯定是有错误的信息！
        3801 /tmp/load_mysql2redis.log
        [root@redis201.oldboyedu.com ~]# 

    (4)验证数据
        [root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021
        127.0.0.1:6379> KEYS *  # 生产环境中千万别用"KEYS *"，因为Redis中可能存储了很多的数据，我这里是实验方便，很明显并没有成功导入3000条数据，因为只有2199条数据，这意味着我们手工导入数据不是特别安全！

        ...

        2186) "city_1970"
        2187) "city_491"
        2188) "city_2249"
        2189) "city_325"
        2190) "city_1411"
        2191) "city_2049"
        2192) "city_374"
        2193) "city_946"
        2194) "city_212"
        2195) "city_1735"
        2196) "city_2643"
        2197) "city_1683"
        2198) "city_1469"
        2199) "city_2763"
        127.0.0.1:6379> 

    (5)粗略验证数据
        [root@redis201.oldboyedu.com ~]# redis-cli -a oldboyedu2021
        127.0.0.1:6379> HGETALL city_1
         1) "id"
         2) "1"
         3) "Name"
         4) "Kabul"
         5) "CountryCode"
         6) "AFG"
         7) "District"
         8) "Kabol"
         9) "Population"
        10) "1780000"
        127.0.0.1:6379> 
        127.0.0.1:6379> HGETALL city_2
         1) "id"
         2) "2"
         3) "Name"
         4) "Qandahar"
         5) "CountryCode"
         6) "AFG"
         7) "District"
         8) "Qandahar"
         9) "Population"
        10) "237500"
        127.0.0.1:6379> 
        127.0.0.1:6379> HGETALL city_3
         1) "id"
         2) "3"
         3) "Name"
         4) "Herat"
         5) "CountryCode"
         6) "AFG"
         7) "District"
         8) "Herat"
         9) "Population"
        10) "186800"
        127.0.0.1:6379> 
        127.0.0.1:6379> HGETALL city_2763
         1) "id"
         2) "2763"
         3) "Name"
         4) "Oyo"
         5) "CountryCode"
         6) "NGA"
         7) "District"
         8) "Oyo"
         9) "&"
        10) "Osun"
        11) "Population"
        12) "256400"
        127.0.0.1:6379> 

2.hash的应用场景总结

    (1)存储部分变更的数据，如学生信息，手机信息，用户信息等。
    (2)当然，字典数据类型是最接近mysql表结构的一种类型，因此是可以做数据库缓存。

    温馨提示:
        如果想要将MySQL的数据导入到Redis数据库，我们可以参考上面手动导入的思路使用代码实现。当然，也可以借助第三方工具，比如阿里巴巴开源的"canal"工具就不错！

    推荐阅读:
        https://github.com/alibaba/canal