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This article mainly explains "what are the basic data types in Redis". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn what are the basic data types in Redis.

Brief introduction of Redis data structure

For redis, all key (keys) are strings. When we talk about the basic data structure, we are talking about the data types that store values, including five common data types, namely: String, List, Set, Zset, and Hash. [related recommendation: Redis video tutorial]

The String string can be a string, an integer or a floating point number to operate on the whole string or part of a string; a self-increment or self-subtraction operation on an integer or floating-point number; a linked list of List lists, each node on the linked list contains a string to perform push and pop operations on both ends of the linked list to read single or more elements; to find or delete elements according to the value Set set contains a collection of unordered sets of strings, including basic methods to see if there are additions, fetches, deletions, etc.; it also includes unordered hash tables containing key-value pairs for calculating intersection, union, difference and other Hash hashes, including methods for adding, getting, and deleting individual elements Zset ordered sets and hashes, which are used to store ordered mappings between string members and floating-point fractions of key-value pairs. The order of elements is determined by the size of the score; the inclusion methods include adding, obtaining, deleting individual elements, and obtaining the element base data structure according to the score range or member to detail the String string.

String is the most basic data type in redis, and one key corresponds to one value.

The String type is binary safe, meaning that the string of redis can contain any data. Such as numbers, strings, jpg images, or serialized objects.

Command u

Command description: use GET to get the value stored in the given key GET nameSET set the value stored in the given key SET name valueDEL delete the value stored in the given key DEL nameINCR add the key stored value plus 1INCR keyDECR subtract the key stored value 1DECR keyINCRBY the key stored value plus the integer INCRBY key amountDECRBY subtract the key stored value minus the integer DECRBY key amount

Command execution

127.0.0.1 world 6379 > set hello worldOK127.0.0.1:6379 > get hello "world" 127.0.0.1 Virtue 6379 > del hello (integer) 1127.0.0.1 world 6379 > get hello (nil) 127.0.0.1 world 6379 > get counter "2" 127.0.0.1 purl 6379 > incr counter (integer) 3127.0.1 0.1 purl 6379 > get counter "3" 127.0.1 0.1 purge 6379 > incrby counter 100 (integer) 103127.0.1 1purl 6379 > get Counter "103" 127.0.0.1 integer 6379 > decr counter (integer) 102127.0.1 purl 6379 > get counter "102"

Actual combat scene

Cache: classic usage scenarios: put common information, strings, pictures or videos in redis, redis as cache layer and mysql as persistence layer to reduce the read and write pressure of mysql.

Counter: redis is a single-threaded model, one command will not be executed until the next, and the data can be landed to other data sources in one step.

Session: common scheme spring session + redis to achieve session sharing

List list

The List in Redis is actually a linked list (Redis uses a double-ended linked list to implement List).

Using the List structure, we can easily implement the latest message queuing function (such as Sina Weibo's TimeLine). Another application of List is message queue, which can take advantage of the PUSH operation of List to store the task in List, and then the worker thread uses the POP operation to fetch the task for execution.

Command u

Command description use RPUSH to push the given value to the right end of the list RPUSH key valueLPUSH push the given value to the left end of the list LPUSH key valueRPOP pops a value from the right end of the list, and returns the pop-up value RPOP keyLPOP pops up a value from the left end of the list and returns the pop-up value LPOP keyLRANGE to get all values of the list in a given range LRANGE key 0-1LINDEX gets the elements in the list through the index. You can also use a negative subscript, with-1 for the last element of the list,-2 for the penultimate element of the list, and so on. LINEX key index

Tips for using lists

Lpush+lpop=Stack (stack)

Lpush+rpop=Queue (queue)

Lpush+ltrim=Capped Collection (finite set)

Lpush+brpop=Message Queue (message queuing)

Command execution

127.0.0.1 ll ls mem (integer) 5127.0.0.1 lrange mylist 0-11) "mem" 2) "ls" 3) "ll" 4) "2" 5) "1" 127.0.0.1mem 6379 > lindex mylist-1 "1" 127.0.0.16379 > lindex mylist 10 # index is not within the range of mylist (nil)

Actual combat scene

Weibo TimeLine: someone posts Weibo and joins the timeline with lpush to show new list information.

Message queue

Set collection

The Set of Redis is an unordered collection of type String. Collection members are unique, which means that there can be no duplicate data in the collection.

Collections in Redis are implemented through hash tables, so the complexity of adding, deleting and searching is O (1).

Command u

Command brief use SADD to add one or more members to a collection SADD key valueSCARD gets the number of members of the collection SCARD keySMEMBER returns all members of the collection SMEMBER key memberSISMEMBER determines whether the member element is a member SISMEMBER key member of the collection key

For other collection operations, please refer to here

Https://www.runoob.com/redis/redis-sets.html

Command execution

Smember myset1) "xiao" 2) "ycf1" 3) "ycf" 127.0.0.1 sadd myset ycf ycf1 xiao ycf 6379 > sismember myset ycf (integer) 1

Actual combat scene

Tag, add tags to users, or users tag messages, so that people with the same or similar tags can recommend things or people to follow.

Like, or click on, collection, etc., can be put into set to achieve

Hash hash

Redis hash is a mapping table of field (field) and value (value) of type string, and hash is particularly suitable for storing objects.

Command u

Command brief use HSET add key value pair HSET hash-key sub-key1 value1HGET to get the value of the specified hash key HGET hash-key key1HGETALL gets all the key value pairs contained in the hash HGETALL hash-keyHDEL if the given key exists in the hash, remove the key HDEL hash-key sub-key1

Command execution

127.0.0.1 hset user name1 ycf (integer) 1127.0.0.1 hset user email1 ycf@163.com (integer) 1127.0.0.1 hset user email1 ycf@163.com > hgetall user1) "name1" 2) "ycf" 3) "email1" 4) "ycf@163.com" 127.0.0.1 > hget user user (nil) 127.0.1 > hget user name1 "ycf" 127.0.1 > hset user name2 xiaoycf (integer) 1127.0.0.1 hset user email2 xiaoycf@163.com (integer) 1127.0.0.1 hgetall user1) "name1" 2) "ycf" 3) "email1" 4) "ycf@163.com" 5) "name2" 6) "xiaoycf" 7) "email2" 8) "xiaoycf@163.com"

Actual combat scene

Cache: can be intuitive, save more space than string, and maintain cache information, such as user information, video information and so on.

Zset ordered set

Redis ordered collections, like collections, are collections of elements of type string, and duplicate members are not allowed. The difference is that each element is associated with a score of type double. Redis sorts the members of the collection from small to large by scores.

The members of an ordered set are unique, but the score can be repeated. The collection is implemented through a hash table, so the complexity of adding, deleting, and finding is all O (1).

Command u

Command description: use ZADD to add a member with a given score to an ordered set ZADD zset-key 178member1ZRANGE gets multiple elements ZRANGE zset-key 0-1 withccoresZREM from the ordered set based on the position of the element in the ordered set. If the given element member exists in the ordered set, remove the element ZREM zset-key member1.

Command execution

127.0.0.1 xiaoycf xiaoycf (integer) 2127.0.0.1 xiaoycf (integer) 2127.0.0.1 xiaoycf > ZRANGE myscoreset 0-11) "xiaoycf" 2) "ycf" 127.0.0.1 xiaoycf 6379 > ZSCORE myscoreset ycf "100"

Actual combat scene

Ranking: collect classic usage scenarios in an orderly manner. For example, websites such as novel videos need to rank the novel videos uploaded by users, which can be ranked according to the number of users' followings, update time, word count and so on.

Thank you for your reading, the above is the content of "what are the basic data types in Redis". After the study of this article, I believe you have a deeper understanding of what the basic data types in Redis have, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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