The redis keys command should be used with caution in the production environment. It is best to shield it

1. First look at the official right keys The description of this command ：

Returns all matching key. keys The time complexity of is O(N),N To execute the database under this command key The number of , constant . redis scanning key It's very fast , The entry notebook is about 40 millisecond 100w individual .

Warning ️：keys Used in production environments can only be performed at extremely low frequencies . Catastrophic performance occurs when large databases are executed . If you need to query some key, Consider using SCAN perhaps sets.

2. keys Why is the command so slow ？

Another way to ask , Why? redis Need to traverse all of key To find what we need key Well ？

1. Redis yes NoSQL Type database , With hash Data structure storage , Therefore, efficient data query can be realized . and hash Structure is very fast for exact lookup , For fuzzy queries , There's nothing we can do .
2. Redis Command execution is single threaded , Only a single command can be executed at one time . A single long command will block subsequent .( Can pass debug sleep 0.1100ms Simulate the execution of long-time commands )

The above two points have caused KEYS Conduct key The query needs to traverse the current db All data for , And when the command execution is completed, subsequent commands will be blocked . So in redis Command executed in , Try to avoid blocking the command for a long time .

3. It is recommended to use Scan Instead of keys

For usage, please refer to ：Redis use scan Fuzzy matching key, Avoid blocking _ dream ~'-CSDN Blog

  use SCAN cursor [MATCH pattern] [COUNT count] Commands are iterated key Traverse （ Limit the... Of a single query key Number ）. This count Not to limit the number of returned results , Instead, it limits the number of dictionary slots that the server can traverse at a single time ( About equal to ). shortcoming ：

1. The same element may be returned more than once . The work of handling duplicate elements is left to the application , for instance , Consider using the elements returned by the iteration only for operations that can be safely repeated multiple times .
2. If an element is added to the dataset during iteration , Or it can be deleted from the dataset during the iteration , So this element might be returned , Maybe not ,redis scan There is only a limited guarantee of the returned result set .
3. If the element is deleted during the iteration , May not be returned .

4. Will want to prohibit the command , Add to the configuration file in the following format :

It is recommended to use... Directly in the configuration file redis Of rename Block these high-risk commands ：

rename-command FLUSHALL ""

rename-command FLUSHDB ""

rename-command KEYS ""

5. SCAN and KEYS The difference between :

  When KEYS When the command is used to process a large database , Or, SMEMBERS The command is used for When dealing with a large set key , They lock redis library , May block the server for several seconds . High concurrency can cause a large number of requests to pile up and cause service avalanche . Some companies directly disable it in the production environment kyes * command . But in redis The server key When the number is small , Use keys There's no problem .

 SCAN Orders and related SSCAN command 、 HSCAN Command and ZSCAN Commands are used to iterate incrementally , They return only a few elements each time they execute , It doesn't block the server , So these commands can be used in the production environment , But not like KEYS command 、 SMEMBERS Problems with orders .

SCAN It has its own problems ：

• Because it's segmentation key, So it will ask for redis The server , This is bound to take the same key,scan Takes longer .
• In the process of incrementally iterating on the bond , The key may be modified , So the incremental iteration command can only provide limited guarantee for the returned elements .

SCAN cursor [MATCH pattern] [COUNT count]

Integrate the following boss articles ：

• redis Execute in a production environment keys Hazards of
• Redis How dare you use the production environment keys？ I advise you to put down your butcher's knife , Repent and be saved ！
• It is forbidden in the production environment Redis perform Keys command