Redis cheat-sheets

This blog contains all the important and basics command related redis

What is Redis

Redis is an open source (BSD licensed), in-memory data structure store used as a database, cache, message broker, and streaming engine. Redis provides data structures such as strings, hashes, lists, sets, sorted sets with range queries, bitmaps, hyperloglogs,geospatial indexes, and streams. Redis has built-in replication, Lua scripting, LRU eviction, transactions, and different levels of on-disk persistence, and provides high availability via Redis Sentinel and automatic partitioning with Redis Cluster.

You can write redis command in any case it don'nt matter, either upper case or lower case

To install redis in Linux

sudo apt-get install redis
#or using snap
sudo snap install redis

To start the redis server

redis-server

To access the redis cli like node and python repl

redis-cli

From now onwards all the operations are performed inside redis cli

Note - To use the redis cli the redis server must be opened which can be started by redis-server command

Basic commands

To quit from redis-cli

127.0.0.1:6379> quit

Set the key-value pair data

#SET (Key) (value)
127.0.0.1:6379> SET name Arshil
OK

Retrieve the value from DB

#GET (Key)
127.0.0.1:6379> GET NAME
"Arshil"

All the data is stored inside redis is type of string

127.0.0.1:6379> SET age 18
OK
127.0.0.1:6379> GET age
"18"

Deleting the key-value

#DEL (key)
127.0.0.1:6379> DEl age
(integer) 1
127.0.0.1:6379> GET age
(nil) #key is deleted

To check whether the particular key exist on DB or not

#EXISTS (key)
127.0.0.1:6379> EXISTS name
(integer) 1 #if key exists
127.0.0.1:6379> EXISTS age
(integer) 0 #if key does not exists

To get all the existed keys in DB

#KEYS (pattern)
127.0.0.1:6379> KEYS *
1) "name"
127.0.0.1:6379> SET post Developer
OK
127.0.0.1:6379> KEYS *
1) "name"
2) "post"

To clear the whole DB

127.0.0.1:6379> FLUSHALL
OK
127.0.0.1:6379> KEYS *
(empty array)

Deleting the data within particular time limit

127.0.0.1:6379> ttl name
(integer) -1 #it has no expression therefore it lives forever
127.0.0.1:6379> EXPIRE name 10 #this key expires after 10 second
(integer) 1
127.0.0.1:6379> ttl name
(integer) 8 #expires after 8 second
127.0.0.1:6379> ttl name
(integer) 4 #expires after 4 second
127.0.0.1:6379> get name
"Arshil"
127.0.0.1:6379> ttl name
(integer) 0 #expires after 0 second
127.0.0.1:6379> ttl name
(integer) -2 #-2 indicates that the key is expired
127.0.0.1:6379> get name
(nil)

Setting expire time along with keys

#SETEX (key) (time in sec) (vakue)
127.0.0.1:6379> SETEX name 20 Arshil
OK
127.0.0.1:6379> ttl name
(integer) 16
127.0.0.1:6379> get name
"Arshil"
#after 20 second
127.0.0.1:6379> ttl name
(integer) -2

Lists in redis

List are the array like data structure used to store multiple value simultaneously with one key

Pushing element in list

#lpush key (values...)
#lpush stands for left push which append element at the beginning of the list
127.0.0.1:6379> lpush languages typescript python c cpp
(integer) 4
#rpush stands for right push which append element at the end of the list
127.0.0.1:6379> rpush languages java c#php javascript
(integer) 8

Retrieving values from the list

#lrange (key) (start index) (end index)
127.0.0.1:6379> lrange languages 0 -1
1) "cpp"
2) "c"
3) "python"
4) "typescript"
5) "java"
6) "c#"
7) "php"
8) "javascript"
127.0.0.1:6379> lrange languages 0 3
1) "cpp"
2) "c"
3) "python"
4) "typescript"

Popping elements from list

#lpop (key) or rpop (key)
127.0.0.1:6379> lpop languages
"cpp"
127.0.0.1:6379> rpop languages
"javascript"
#values after element are pooped
127.0.0.1:6379> lrange languages 0 -1
1) "c"
2) "python"
3) "typescript"
4) "java"
5) "c#"
6) "php"

Sets in redis

Sets are similar to list except is is used to store all the unique values in record

Adding element in sets

#SADD Key (values)
127.0.0.1:6379> SADD nums 1 2 3 4 5
(integer) 5
127.0.0.1:6379> SADD cars "Royce Royale" Benz Mustang #you can use "" if you have multiple word item
(integer) 3
#We can't add same values again 
127.0.0.1:6379> SADD nums 1
(integer) 0
127.0.0.1:6379> SADD cars Benz
(integer) 0

Retrieving values from sets

#SMEMBERS (key)
127.0.0.1:6379> SMEMBERS nums
1) "1"
2) "2"
3) "3"
4) "4"
5) "5"
127.0.0.1:6379> SMEMBERS cars
1) "Mustang"
2) "Benz"
3) "Royce Royale"

Removing item from sets

#SREM key (values...)
127.0.0.1:6379> SREM cars Mustang "Royce Royale"
(integer) 2
127.0.0.1:6379> SREM nums 1 3 4 5
(integer) 4
#values after elements are removed
127.0.0.1:6379> SMEMBERS nums
1) "2"
127.0.0.1:6379> SMEMBERS cars
1) "Benz"

Hashes

Hashes are just another key value pair inside key value pair up to one level consider this json example

{
    "name":"Eren",
    "friends":{
        "name":"Armin",
    }
}

Setting hash value

#HSET Key (field) (value) (fields... values...)
127.0.0.1:6379> HSET characters name Eren friend armin
(integer) 1

Retrieving hash value

#HGET Key field
127.0.0.1:6379> hget characters friend
"armin"
127.0.0.1:6379> hget characters name
"Eren"
#get all values for specific hash
#HGETALL key
127.0.0.1:6379> HGETALL characters
1) "name"
2) "Eren"
3) "friend"
4) "armin"

Deleting fields in hash

#HDEL key field
127.0.0.1:6379> HDEL characters friend
(integer) 1
#after deleting key 'friend'
127.0.0.1:6379> HGETALL characters
1) "name"
2) "Eren"

Check whether particular key exist or not

#HEXIST key field
127.0.0.1:6379> HEXISTS characters name
(integer) 1
127.0.0.1:6379> HEXISTS character friend
(integer) 0

Usage of redis in real world example

Basic node express server code without using redis

app.get("/photos", async (req, res) => {
  const albumId = req.query.albumId;
  const { data } = await axios.get(
    "https://jsonplaceholder.typicode.com/photos",
    { params: { albumId } }
  );
  res.send(data);
});
app.get("/photos/:id", async (req, res) => {
  // can be anything (fetching from db or any other expensive task)
  const { data } = await axios.get(
    `https://jsonplaceholder.typicode.com/photos/${req.params.id}`
  );
  res.send(data);
});

Install the redis

npm i redis
#or
yarn add redis

Setup redis in node js

const redisClient = Redis.createClient();
(async () => {
  await redisClient.connect();
})();
// create js utility fn to store and retrieve cache from db
function getOrSetCache(key, cb) {
  return new Promise(async (resolve, reject) => {
    const data = await redisClient.get(key);
    if (data != null) resolve(JSON.parse(data));
    const freshData = await cb();
    redisClient.setEx(key, DEFAULT_EXPRESSION, JSON.stringify(freshData));
    resolve(freshData);
  });
}
// using function in express routes
app.get("/photos", async (req, res) => {
  const albumId = req.query.albumId;
  const photos = await getOrSetCache(`photos?albumId=${albumId}`, async () => {
    const { data } = await axios.get(
      // can be anything (fetching from db or any other expensive task)
      "https://jsonplaceholder.typicode.com/photos",
      { params: { albumId } }
    );
    return data;
  });
  res.json(photos);
});
app.get("/photos/:id", async (req, res) => {
  const id = req.params.id;
  const photos = await getOrSetCache(`photos:${id}`, async () => {
    const { data } = await axios.get(
      `https://jsonplaceholder.typicode.com/photos/${req.params.id}`
    );
    return data;
  });
  res.json(photos);
});

Results without using redis

Time taken to process endpoint /photos 644ms

Time taken to process endpoint /photos/4 837ms

Results after using redis cache

(note that every endpoint needs an hit to store the data in cache after initial hit this record is measured)

Time taken to process endpoint /photos 18ms

Time taken to process endpoint /photos/4 7ms

Redis collection

127.0.0.1:6379> keys *
1) "photos?albumId=1"
2) "photos?albumId=20"
3) "photos:4"
4) "photos?albumId=undefined"

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For more reference click here

I hope you now your concepts related redis is cleared.