Redis basics and data types

What is Redis

• Redis (Remote Dictionary Server): remote dictionary service
• It is an open source log-type, key-value database that is written in C language, supports the network, can be based on memory and can be persisted, and provides APIs in multiple languages
• One of the most popular NoSQL technologies at the moment, also known as structured database

What can Redis do

• Memory storage and persistence (memory is lost when power is off, so persistence is very important)
• High efficiency, can be used for cache
• Publish and Subscribe System
• Map information analysis
• Timers, counters, page views

Features of Redis

• Various data types
• Can be persistent
• Transaction function
• Can do cluster

Install under Windows

1. download
2. Unzip to your own environment directory
3. Run in the environment directory: redis-server.exe redis.windows.conf
4. Enter redis-cli.exe, enter ping, test the connection

Install under Linux

1. Download the compressed package: wget http://download.redis.io/releases/redis-5.0.8.tar.gz
2. Unzip to the opt path: tar -zxvf redis-5.0.8.tar.gz
3. Install gcc: yum install gcc-c++
4. cd /redis-5.0.8 —> make
5. make install
6. Linux will be installed to /usr/local/bin by default

Redis configuration under Linux

1. Create a directory to save your own configuration files under /usr/local/bin: mkdir myconfig
2. Copy the Redis configuration file: cp /opt/redis-5.0.8/redis.conf myconfig
3. File monize no change monize yes , so after Taiwan way to start

Start Redis under Linux

• Execute under /usr/local/bin: redis-server myconfig/redis.conf start Redis
• Execute under /usr/local/bin: redis-cli -h host -p port -a password to enter Redis client
• The client executes shutdown and then exit closes Redis and exits the client

Redis benchmark

Official performance test tool

• Test: 100 concurrent connections 100000 requests

  Execute under /usr/local/bin: redis-benchmark -h localhost -p 6379 -c 100 -n 100000

Redis basic commands

The following commands are executed under the Redis client

• Redis has 16 databases by default, number 0-15, and number 0 is used by default

  select n (select 3) command: switch the database

• dbsize command: view the current database size

• keys *Command: View all keys of the current database

• set key_name key_value: add a key to the current database

• flushdb command: clear the current database

• flushall: flush all databases

• exists key_name: If the key exists, return 1, otherwise return 0

• mave key_name: remove the target key

• expire key_name num (Arabic numerals): Set the expiration time for the target key

• ttl key_name: View the remaining time of the target key

• type key_name: View the type of target key

Redis data type

Five basic data types

• String

  Usage scenario : The value of the String type can be a number in addition to a string; therefore, it can be used to implement counters, count the number of units, object cache, and web page cache

  Commonly used commands:

  • append key_name value: append content to the target key, if the key does not exist, it is equivalent to adding a key
  • strlen key_name: View the length of the value corresponding to the target key
  • incr key_name: target key value +1, which can be used to achieve real-time data of the website, such as reading volume (when the key value is a number, the Redis background will automatically convert it to Integer before operating)
  • decr key_name: target key value -1
  • incrby/decrby key_name num (Arabic numerals): increase/decrease the specified value
  • getrange key_name num1 num2: Get the string range
  • setrange key_name num xx: modify the string value from num to xx
  • mset k1 v1 k2 v2 k3 v3: set multiple keys at once
  • mget k1 k2 k3: get multiple values ​​at once
    • Mset and mget are atomic operations, either all succeed or fail
  • setex key_name num key_value: Create the target key and set the expiration time
  • setnx key_name key_value: If this key does not exist, create the target key
  • set user:1 {name:waston,age:3}: set a user:1 object value as a json string
  • set item:{id}:value: such as set book:3:views, the number of page views of Book 3
  • getset key_name value: get the target key first, and then set the value to the target key
  • lset list_name index value: put a value to the specified subscript of the target list, the list and subscript must exist!

• List

  In Redis, the underlying data structure of the list is a linked list, which can be used as a stack, queue, or blocking queue

  **Use scenario: **Message queue

  Commonly used commands:

  list_name is still stored as a key in Redis

  • lpush list_name value: add value to the left (head) of the target list
  • rpush list_name value: add value to the right (tail) of the target list
  • lrange list_name num1 num2: view the values ​​in the target list; lrange list_name 0 -1: view all
  • lpop list_name: The target list pops a value on the left (head)
  • rpop list_name: The target list pops a value on the right (tail)
  • lindex list_name num (starting from 0): Get the num+1 value from the left of the target list
  • llen list_name: Get the length of the list
  • lrem list_name value: remove all values ​​in the target list
  • lrem list_name num value: remove num values ​​from the target list, from left to right
  • ltrim list_name num1 num2: intercept the target list; retain the value of num1 to num2
  • rpoplpush a_list b_list: Pop a value from the right side of a_list and put it in b_list
  • linsert list_name before/after value1 value2: add value2 to the left/right of value1 in the target list

• Set

  Values ​​in Set cannot be repeated

  **Use scenario: **Display of common attributes such as common concern and common hobbies among users; recommended by friends

  Commonly used commands:

  • sadd set_name value: add an element to the target set
  • smembers set_name: View the elements in the target set
  • sismember set_name value: Determine whether value is in the target set (1: exists 0: does not exist)
  • scard set_name: the number of elements in the target set
  • srem set_name value: remove the value element in the target set
  • srandmember set_name (num): randomly take out one (num) element from the target set
  • spop set_name: randomly pop an element from the target set
  • smove set1 set2 value: Move the value in set1 to set2
  • sdiff set1 set2: return elements in set1 but not in set2
  • sinter set1 set2: Returns the elements jointly owned by set1 and set2
  • sunion set1 set2: returns all elements in set1 and set2, only one of the same element is returned

• Hash

  Map collection, key-map; the essence is not much different from the String type, the value in the string becomes the key-value

  Hash is more suitable for object storage, string is more suitable for general string storage

  **Use scenario: **Use a hash to store a series of information of a user

  Commonly used commands:

  • hset hash_name key_name value: create a hash
  • hget hash_name key_name: Get the value corresponding to the target key in the target hash
  • hmset hash_name k1 v1 k2 v2: Create multiple values
  • hmget hash_name k1 k2: Get multiple values
  • hdel hash_name key_name: delete the target key and corresponding value in the target hash
  • hlen hash_name: View how many keys are in the target hash
  • hexists hash_name key_name: Determine whether the target key exists in the target hash
  • hkeys hash_name: View all keys in the target hash
  • hvals hash_name: View all values ​​in the target hash
  • hincrby hash_name key_name 1/-1: Make the value of the target key +1 or -1
  • hsetnx hash_name key_name value: create when the target key does not exist

• Zset

  Ordered set

  A value is added to the set for sorting

  **Use scenario: **Leaderboard, data weighting

  Commonly used commands:

  • zadd set_name score value: create a target zset, and add a value score
  • zadd set_name n1 v1 n2 v2: create multiple, eg: zadd salary 100 sam 200 kim
  • zrangebyscore set_name -inf +inf: target zset is output in ascending order according to score, the range is -inf to +inf, which means positive or negative infinity is the full range
  • zrevrange set_name +inf -inf: output in descending order
  • zrangebyscore set_name -inf +inf withscores: sort the output with score
  • zrem set_name value: remove the specified element in the target zset
  • zcard set_name: Get the number of elements in zset
  • zcount set_name num1 num2: Get the number of elements between num1 and num2

Three special types

• geospatial

  Geographical location; the bottom layer is implemented by zset

  **Use scenario: **Location, nearby people, distance calculation

  Commonly used commands:

  1. Add geographic location: geoadd key_name longitude (longitude) latitude (latitude) place_name (eg: geoadd china:city 116.40 39.90 beijing)

     Generally download city geographic data and import it in one time using java program

  2. Get the latitude and longitude data of the target bottom point: geopos key_name place_name1 place_name2 (one or more)

  3. Return the distance between two places: geodist key_name place1 place2 unit

     unit is the unit, it can be km m mi ft

  4. With the given latitude and longitude as the center, find the elements within a certain radius: georadius key_name longitude (center longitude) latitude (center latitude) radius (radius) unit (unit) xxx (additional parameters)

     The additional parameter is withdist, the straight line distance is added to the result; withcoord, the latitude and longitude is added; count num, the number of results is limited

  5. The query is centered on the specified location and the elements within the specified range: georadiusbymember key_name place_name radius unit

  6. Return the latitude and longitude of the specified place in string format: geohash china:city place_name

  7. Remove target location: zrem key_name place_name

  8. All zset related commands can be used directly...

• Hyperloglog

  A data structure for cardinal statistics

  Cardinality , that is, the number of remaining elements in an array after removing duplicate elements; such as {1,3,5,5,7} after deduplication {1,3,5,7}, the base is 4

  **Use scenario: **Record the UV of the webpage (a person visits multiple times, press once), counting statistics

  Commonly used commands:

  1. Create a Hyperloglog: pfadd key_name value1 value2…
  2. View the number of elements in the specified Hyperloglog: pfcount key_name
  3. Merge Hyperloglog (union): pfmerge key_name key1 key2

• Bitmap

  Bitmap, can be regarded as an array

  **Application scenario: **There are only two statistics, 0 means one situation, 1 means another situation. Such as: login, check in

  Commonly used commands:

  1. Set the value in the target bitmap target index: setbit map_name index 0/1
  2. Get the value of the target bitmap target index: getbit map_name index
  3. Count the number of elements with a value of 1 in the target bitmap: bitcount map_name