Some useful commands in Redis

Redis is important component when we want to design scalable system. It is used as cache for our system. So, in this article, we will learn how to use some commands in Redis.

Let’s get started.

How to install redis-cli
Connect with local/remote redis server
Get/set commands
Check commands
Query commands
Modification commands
Wrapping up

How to install redis-cli

Install redis-cli on Windows

To install it on Windows, we can visit some webpages to download a redis executable file.
- tporadowski/redis
- microsoftarchive/redis
Install redis-cli on Ubuntu

Belows are some steps to install redis-cli in Ubuntu.
1. Update the apt package
```
 sudo apt update
```
2. Install redis-tools
```
 sudo apt install -y redis-tools 
```

Connect with local/remote redis server

By default, Redis runs without username and password, the default port is: 6379.

# Go to the folder of Redis
# 1st - Run Redis client in local host
redis-cli

# 2nd - Connect to the remote server
redis-cli -h <ip_addr> -p <port_number> -a <password>

Get/set commands

Create / Update data

 set key value

 # set if not exist value in key
 setnx key value

For example:

 set phone_type Iphone

Get data
```
 get key
```
For example:
```
 get phone_type
```

Modify key’s name

 renamenx <key_name> <new_key_name>

For example:

 renamenx phone_type phonetype

Check commands

Check whether key is existed or not
```
 exists key
```
For example:
```
 exists phone_type
```

Query commands

Find all keys with patterns
```
 keys pattern
```
For example:
```
 keys *type
```
Especially, if we want to list all keys in Redis.
```
 keys *
```
Note:
- Time complexity: O(N) with N being the number of keys in the database, under the assumption that the key names in the database and the given pattern have limited length.
- All redis commands are single thread and will block the server. The only difference is that keys has the potential of blocking server for longer when querying a large data set.
  
  So, with version 2.8 or later, use scan is a superior alternative to keys because it does not block the server nor does it consume significant resources.
```
  redis-cli --scan --pattern '*'
```
Get random key from Redis
```
 randomkey
```
Get the data type of the value stored in the key
```
 type key
```
For example:
```
 type phone_type
```

Get the value of a key depends on its type

 # string data type
 get <key>

 # hash data type
 hgetall <key>

 # list data type
 lrange <key> 0 -1

 # set data type
 smembers <key>

 # zset data type
 zrange <key> 0 -1 withscores

Modification commands

Increment value in key
```
 incr key
```
For example:
```
 set num 2
 incr num
```
Increment the integer value of a key by the given amount
```
 incrby key increment
```
For example:
```
 incrby num 5
```
Increment the float value of a key by the given amount
```
 INCRBYFLOAT key increment
```
Decrement the integer value of key by one
```
 decr key
```
For example:
```
 decr num
```
Decrement the integer value of a key by the given number
```
 decrby key decrement
```
For example:
```
 decrby num 4
```
Delete key
```
 DEL key
```
Set expiration time for key
```
 expire key <expiration_time_ms>
```
Returns the number of seconds until a key is deleted
```
 ttl key
```
Clear expired time of key
```
 persist key
```

Wrapping up

Understanding about the commands of Redis.

Refer:

https://gist.github.com/LeCoupa/1596b8f359ad8812c7271b5322c30946

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