Six types of Redis features and usage scenarios

Six features of Redis

L Strings

L HASHS

L Lists

L Sets

L Sorted Sets

L PUB/SUB Application Scenarios for Redis features Strings

The Strings data structure is a simple key-value type, and value is not only a string, it can also be a number. Common Methods

Method	Description	Characteristics
Set	Sets the value of the key corresponding to string type
Get	Gets the value of the string corresponding to the key, if no return nil exists
Setnx	Set can be a value of type string, if key exists return 0 does not overwrite, there is no return 1	NX means not exist Set the value of a key, only if the key does not exist
Setex	The value of the set key is a string of type value and specifies the validity period for this key value Setex Key seconds value	Example: Setex mykey 10 Hello
SetRange	Sets the substring of the value of key	SetRange Key Location Replacement content If the replacement content does not have the original value length, the remaining contents of the original value are preserved
Mset	Set the value of multiple keys at once, successfully return OK, fail to return 0, success is successful, or all failed successfully.	Mset key1 Content One key2 content two
Msetnx	Setting the value of multiple keys at once, successfully returning OK, failing to return 0, not overwriting values that already exist, succeeding successfully, failing all.
Getset	Sets the value of key and returns the old value of key	Getset Key Newvaluse
GetRange	Gets the value substring corresponding to key	GetRange key 0 5//Get first 6 characters
Mget	Bulk acquisition	Mget key1 Key2 Key3//No setting returns empty
incr	Increase the value of the key and return the new value	+1
Incrby	The value specified for the possible value plus,	Key if not present will set key and value is 0 Incrby Key1 5//value of Key1 plus 5
Decr	Reduce the value of a key by reducing the operation	-1
Decrby	Subtracts the specified value from the value of key
Append	Appends value to the string of the specified key, returning the new string length
Strlen	Takes the length of the value of the specified key

Usage Scenarios

General Key-value Cache app. Regular count: Number of Weibo, number of fans HASHS

In memcached, we often package structured information into HashMap, which is stored as a string value after the client is serialized, such as the user's nickname, age, gender, integral, and so on, when it is necessary to modify one of these items, it is usually necessary to remove all values after deserialization, Modify the value of an item, and then serialize the store back. This not only increases the overhead, but also does not apply to some scenarios where concurrent operations are possible (for example, two concurrent operations need to modify the integral). The hash structure of Redis allows you to modify only one item property value just as you would update a property in a database .

It is a string type of field and value mapping table, its addition and deletion are average, hash is particularly suitable for storing objects, for storing objects into a string, hash will occupy less memory, and can more convenient access to the entire object. It is completely similar to the Java HashMap method

Method	Description	Characteristics
Hset	Set a hash field to the specified value, and if key does not exist, create it first.	Hset tab KE1 VAL1
Hget	Get a field value for a hash	Hget Tab KE1
Hsetnx	Like a string is just a hash of the operation
Hmset	Bulk Set Hash content
Hmget	Get all key values of the hash table	Hmget Key Field1 Field2
Hincrby	Add value to a field in a hash table
Hexists	Determine if a key exists in the hash table
Hlen	Returns the number of keys in the hash table
Hdel	Deletes a key value pair for the specified hash table
Hkeys	Returns all keys in the hash table
Hvals