Six types of Redis features and usage scenarios

Source: Internet
Author: User
Tags hash redis
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

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