What are the common commands for keys and strings in Redis?

Redis related knowledge

The default port number of Redis is 6379

The default 16 databases, similar array subscripts start from 0, The initial default is to use library No. 0.
Use the command select <dbid></dbid> to switch databases. Such as: select 8.
Unified password management, all libraries have the same password.

dbsizeView the number of keys in the current database.
flushdbClear the current library.
flushall Kill all libraries.

Redis is a single-threaded multi-channel IO multiplexing technology.
Multiplexing refers to using one thread to check the readiness status of multiple file descriptors (Socket), such as calling the select and poll functions and passing in multiple file descriptors. If one file descriptor is ready, then Return, otherwise block until timeout. After getting the ready state, the actual operation can be performed in the same thread, or thread execution can be started (such as using a thread pool).

Serial VS Multi-thread lock (memcached) VS Single-threaded multi-channel IO multiplexing(Redis)
Redis and Memcache Three differences:

• Support multiple data types

• Support persistence

• Single thread multiple Road IO multiplexing

Data types in Redis

redis key

keys *: View all keys in the current library (matching: keys *1)

##exists key: Determine whether a key exists.
type key: Check what type your key is.
del key: Delete the specified key data,

unlink key: Select non-blocking deletion based on value. Only keys are deleted from keyspace metadata, and the actual deletion will be performed asynchronously later. .
expire key 10: 10 seconds, set the expiration time for the given key,
ttl key: Check how many seconds there are left to expire, -1 means never Expired, -2 means expired.

selectCommand to switch databases,
dbsizeView the number of keys in the current database.
flushdbClear the current library.
flushallkill all libraries

String type is binary safe. It means that Redis string can contain any data. For example, jpg pictures
or serialized objects.
String type is the most basic data type of Redis. A string value in Redis can be up to 512M.

set : Add key-value pairs. When a key with a set value is set to a new value, the new value will overwrite the old one.

*NX: When the key does not exist in the database, the key-value can be added to the database.

*XX: When the key exists in the database, key-value can be added to the database, which is mutually exclusive with NX parameters.
*EX: Key timeout seconds.
*PX: key’s timeout in milliseconds, mutually exclusive with EX.

get Query the corresponding key value.
append Append the given Append to the end of the original value,
strlen Get the length of the value.
setnx Set the value of the key only when the key does not exist.

incr

Can only operate on numeric values. If it is empty, the new value is 10

decr

Can only operate on numeric values. If it is empty, the new value is -1.

inrjy/ decrby <step> Increase or decrease the numerical value stored in key. Custom step size. </step>

incr and decr are atomic operations
but i in java is not an atomic operation

mset ....

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