Redis

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June 6, 2021

1:46 pm

35 Comments on Redis

Database

Redis Playground

https://try.redis.io/

Note: This try redis io is community version on web so few commands might not work. To use redis’s full power you can download and install on your local system

Redis is an in-memory data structure store, used as a distributed, in-memory key–value database, cache and message broker, with optional durability. Redis supports different kinds of abstract data structures, such as strings, lists, maps, sets, sorted sets, HyperLogLogs, bitmaps, streams, and spatial indices.

Installation

To install redis on windows download msi package from here
https://github.com/microsoftarchive/redis/releases/

For Linux Distr

sudo apt-get install redis-server

To install PHPRedis client use following command

sudo apt-get install php-redis
#for specific version
sudo apt-get install php7.4-redis

To verify redis installed in your system
Note: On windows you might need to add redis exe path in environment variables

redis-cli PING

To see all keys

KEYS *

DATATYPES

  • string
  • list
  • set
  • sorted set
  • hash
  1. String
    Syntax to set string value
SET key value [EX seconds] [PX milliseconds] [NX|XX]

To set only string value

SET keyname value

To check whether key exist or not

EXISTS keyname

Get key’s value

GET keyname

To delete any specific key

DEL keyname

To delete all keys

FLUSHALL

SET string with expiry

SET key value
EXPIRE key expiry-time-in-seconds
#shortcut
SET key value EX expiry-time-in-seconds

To check expiry time of any key

TTL key

SET string values using key:spaces
This is required when you want to set values related to one entity

SET key:space value

2. List or Stack

To set list use LPUSH

LPUSH key value1
LPUSH key value2
LPUSH key value3
OR
LPUSH key value1 value2 value3

To get length of list

LLEN key

To access any value of list you need to use LRANGE

LRANGE key from-index to-index

Use -1 in to-value to get all elements from list

LRANGE key 0 -1

To get specific index value
NOTE this will act like stack so LIFO algorithm will apply here i.e. index 0 will give you last inserted/pushed value

LINDEX key 0

LPUSH and RPUSH (left and right push)

LPUSH key value
RPUSH key value

LPOP and RPOP

LPOP key
RPOP key

Remove specific element from list

LREM key count value

3. Sets

Set is similar to list the main difference is it does not allow duplicate members
Order is not maintained in set

To add member in sets

SADD key value1 value2 value3

To view members of sets

SMEMBERS key

To remove member from sets

SREM key member

To get length of Sets

SCARD key

Compare Sets

SINTER set1 set2
SDIFF set1 set2
SUNION set1 set2

4. Sorted Sets

Sorted set are similar to sets the major difference is it stored members based on score i.e. sorted by score

ZADD key score member

To add multiple members

ZADD key rank1 member1 rank2 member2

To get count of sorted sets

ZCOUNT key

To See all members of sorted sets

ZRANGE key 0 -1

To get rank(index) of specific member

ZRANK key member

To get score of specific member

ZSCORE key member

To remove member from sorted sets

ZREM key member

5. Hashes

Hash is used to set field value pair it is similar to associative array

To set hash

HGET key field1 value1
HGET key field2 value2

To get field value

HGET key field

To get all field values

HGETALL key

To get length of hash key

HLEN key

To add field values at once

HMSET key field1 value1 field2 value2 field3 value3

To get values at once

HMGET key field1 field2 field2

To delete specific field from hash

HDEL key field1 field2

Assignment (set and get values of each type)

  1. Create string name age and city and set value in it
  2. Create List of fruits, weekdays, planets and set values in it
    Print length and values of list
  3. Create Sets of employees and managers
    Print length and values of Sets
  4. Create Hash record1, record2, record3 and add fields name age city in each hash
    Print length and values of each hash

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