Redis

Redis is a NOSQL database in which data is stored in key-value pairs.
Redis stores data on main memory meaning its fast but its volatile unlike database systems like PostgreSQL which stores data on disk.

Overview

In an application with a server and a database, accessing information on the database will cause latency.

Key-Value databases like redis is often kept in front of those databases and access operations takes 2 steps:

1. If the information is in the cache,cache hit, the application retreives the information from redis and sends it to the client
2. If not,cache miss, the application takes the information from the database , sends it to the client and stores it in the cache.

With these 2 steps and given that main memory has lower latency than disk, we can say that redis can be used to store and access frequent, recent data and expensive operations thereby making applications 10 to 50x faster.

It is thereby a fact that if at all you are going to building an application that is going to be scalable in the future, Redis(or databases similar to Redis) is indispensable.

Questions

1. Is Redis Open Source?: Yes, Redis is open source with a special kind of license but there are alternatives like KeyDB by Snapchat and Memcached that are open source.KeyDBis a fork of Redis but as of now can only run on Linux.

2. Does Redis Support Windows?: No, Redis does not support Windows, but you can install WSL/Ubuntu and install redis using
   

sudo apt install redis

1. I am using WSL, Why isn't redis server working on my system: When running on WSL, you can run redis-server using

redis-server --port 6000

where 6000 is the port on your local server you want to run it on. (i.e. 127.0.0.1:6000).

Most issues are due to the fact that the default port that redis-server is using is already being used

1. Are there client libraries for Redis?: Actually yes. you can find them on the Redis website or you can build one yourself.

Installing Redis

On Linux, installing redis is as simple as

sudo apt install redis

oron Mac:

brew install redis

Running Redis

You need to have2 instances of your terminalon

on the first one to run your server

redis-server -port  

and on the second one to run your client

redis-cli

When building a web app, you dont need to run the clientbut the server needs to be running

Redis Concepts

There are 3 main concepts in redis you should understandor 4

1. Key-Value Pairs
2. Lists
3. Sets
4. Hashes

All other data structures are mainly an advanced implementation of the first

Bylist, I meantarraynotlinked listand thats what redis calls it.

Key-Value Pairs

Key-Value pairs are a common data structure in most programming languages.

1. In Python it is called dictionaries ordictin short

2. In Javascript it is calledMaps

3. In C# it is calledDictionaries

There are 6 main operations for key-value pairs in Redis

時間ベースの操作もあります。時間ベースの操作では、キーは設定された期間だけキャッシュ内にあり、時間が経過するとキャッシュはキーを削除します。

主に 2 つの時間ベースの操作があります

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