Introduction to redis commands for batch deletion

redis implements batch deletion:

1. Access the redis root directory cd /usr/local/redis-2.8.19

2. Log in to redis : redis-cli -h 127.0.0.1 -p 6379 (where 127.0.0.1 can be written as the IP address of the server, and 6379 is the port number)

3. View all key values: keys *

4. Delete the value of the specified index: del key

5. Clear the data of the entire Redis server: flushall

6. Clear all keys in the current library: flushdb

[First method]:

The following is a batch deletion of all redis data starting with "key_", the number of which is 100

redis-cli -h (IP地址) -p 6379 (端口号：6379) KEYS key_* | xargs redis-cli (-h (IP地址) -p 6379 (端口号：6379)) del 
 
=>[执行后返回的结果影响数量]：(integer) 100[数量100个]

[Specific usage of the DEL function in the above command]:

DEL key [key ...]

Delete one or more given keys.

Non-existing keys will be ignored.

Time complexity:

O(N), N is the number of deleted keys.

Delete a single string type key, the time complexity is O(1).

Delete a single list, set, ordered set or hash table type key, the time complexity is O(M), M is the number of elements in the above data structure.

Return value:

The number of deleted keys.

[Example]:

#  删除单个 key
redis> SET name huangz
OK
 
redis> DEL name
(integer) 1
 
# 删除一个不存在的 key
redis> EXISTS phone
(integer) 0
 
redis> DEL phone # 失败，没有 key 被删除
(integer) 0
 
# 同时删除多个 key
redis> SET name "redis"
OK
 
redis> SET type "key-value store"
OK
 
redis> SET website "redis.com"
OK
 
redis> DEL name type website
(integer) 3

[Second method]:

Disadvantages of the first method: Such a disadvantage requires establishing a connection every time, which is small. It's acceptable if the quantity is large, but the efficiency is not good if the quantity is large.

Through the built-in Lua interpreter, you can use the EVAL command to process Lua scripts:

redis-cli -h(IP地址) -p 6379(端口号：6379) --EVAL "return redis.call('del', unpack(redis.call('keys', ARGV[1])))" 0 'Volume:*'

[Note]: However, this processing method will cause problems with unpacking the lua function when the volume is large. , an error will be reported

'''
(error) ERR Error running script (call to f_e177a091510d969af3b388ee986dbe6658df6b57): @user_script:1: user_script:1: too many results to unpack
'''

[After optimization of the second method]:

[Note]: First define an array keys, which stores all the pattern matching keys ending with 'Volume:' key, and then a for loop, processing 5000 keys each time, that is to say, del 5000 keys each time

redis-cli -h(IP地址) -p 6379(端口号：6379) --EVAL "local keys = redis.call('keys', ARGV[1]) 
	for i=1,#keys,5000 
		do 
			redis.call('del', unpack(keys, i, math.min(i+4999, #keys))) 
		end 
		return #keys" 0 'Volume:*'

[Disadvantages of the second method]:

KEYS operations are prohibited online of!

Redis is single-threaded. If the volume is large, the keys will be traversed, which will cause blocking, so other clients will not be able to connect!

[The third method]:

Since redis2.8, the scan command has been supported. Pattern matching can take the following form to batch delete a large number of keys

redis-cli -a youpassowrd -n 0 -p 6379 --scan --pattern "Volume:*" | xargs -L 5000 redis-cli -a youpassword -n 0 -p 6379 DEL

[Result]:

'''
 /work/app/redis/bin/redis-cli -a youpassword -n 0 -p 6379 --scan --pattern "Volume:*" | xargs -L 5000 /work/app/redis/bin/redis-cli -a youpassword -n 0 -p 6379 DEL
(integer) 5000
(integer) 5000
(integer) 5000
(integer) 5000
(integer) 5000
(integer) 5000
(integer) 5000
(integer) 207
'''

For more redis knowledge, please pay attention to the redis introductory tutorial column.

The above is the detailed content of Introduction to redis commands for batch deletion. For more information, please follow other related articles on the PHP Chinese website!