Redis Data Management

Redis Data Management

• Redis uses a key-based data structure.
• It belongs to the family of databases called key-value stores.
• Data is stored as key = value.
• Values can be:
  • String
  • List
  • Hash
  • Set
  • And more…
• You can only retrieve data if you know the exact key used to store it.

Commands

Keys Naming Conventions

• Keep it simple but robust: Choose clear and meaningful names for your keys.
• Avoid very short keys: They can be unclear and hard to manage.
• Use a logical schema: Design your key names based on your database structure. For example, use object-id:id.
• Maximum key size: Keys can be up to 512MB in size.
• Binary safe: Redis keys can be any binary sequence, meaning they can include any characters.
• Empty string: An empty string is also a valid key in Redis.

Redis Naming Convention

❯ Set key

❯ Syntax: set [key] [value]

127.0.0.1:6379> set cloudsimplify:user:100:name github
OK

❯ Get key

❯ Syntax: get [key]

127.0.0.1:6379> get cloudsimplify:user:100:name
"github"

❯ Delete keys (Integer 1 means operation was successful)

❯ Syntax: del [key...]

127.0.0.1:6379> del cloudsimplify:user:100:name
(integer) 1

❯ Check if a key exists or not (Integer 0 means key not exists)

❯ Syntax: exists [key...]

127.0.0.1:6379> set cloudsimplify:user:100:name github
OK
127.0.0.1:6379> exists cloudsimplify:user:100:name
(integer) 1
127.0.0.1:6379> del cloudsimplify:user:100:name
(integer) 1
127.0.0.1:6379> exists cloudsimplify:user:100:name
(integer) 0

How Redis Handles Key Expirations?

• Normal keys: These are created without any expiration time.
• Expired keys: These have expiration information stored as a Unix timestamp (in milliseconds).

Redis expires keys in two ways:

1. Passive Expiration:
   • A key expires passively when a client tries to access it and it’s found to have timed out.
2. Active Expiration:
   • Redis actively checks for expired keys 10 times per second by:
     • Testing 20 random keys that have expiration times.
     • Deleting any keys that are found to be expired.
     • If more than 25% of the tested keys are expired, Redis repeats the process.

❯ Define key with expiration

❯ Syntax: set [key] [value] ex [ttl]

127.0.0.1:6379> set cloudsimplify:user:100:password secretpasswd ex 86400
OK

❯ Check ttl on key in sec

❯ Syntax: ttl [key]

127.0.0.1:6379> ttl cloudsimplify:user:100:password
(integer) 86252

❯ Set expiration on key in sec

❯ Syntax: expire [key] [ttl]

127.0.0.1:6379> expire cloudsimplify:user:100:password 300
(integer) 1
127.0.0.1:6379> ttl cloudsimplify:user:100:password
(integer) 297

❯ Set expiration on key in ms

❯ Syntax: pexpire [key] [ttl(ms)]

127.0.0.1:6379> pexpire cloudsimplify:user:100:password 300000
(integer) 1

❯ Check ttl on key in ms

❯ Syntax: pttl [key]

127.0.0.1:6379> pttl cloudsimplify:user:100:password
(integer) 297541

❯ Sets the string value and expiration time of a key. Creates the key if it doesn’t exist

❯ Syntax: setex [key] [ttl] [value]

127.0.0.1:6379> setex cloudsimplify:user:100:password 300 secretpasswd
OK
127.0.0.1:6379> ttl cloudsimplify:user:100:password
(integer) 297

❯ Sets both string value and expiration time in milliseconds of a key. The key is created if it doesn’t exist

❯ Syntax: psetex [key] [ttl(ms)] [value]

127.0.0.1:6379> psetex cloudsimplify:user:100:password 300000 secretpasswd
OK
127.0.0.1:6379> pttl cloudsimplify:user:100:password
(integer) 296337
127.0.0.1:6379> ttl cloudsimplify:user:100:password
(integer) 294
127.0.0.1:6379>

❯ Remove the expiration from the key (Integer 1 means expiration removed)

❯ Syntax: persist [key]

127.0.0.1:6379> setex cloudsimplify:user:100:token 300 sometoken
OK
127.0.0.1:6379> ttl cloudsimplify:user:100:token
(integer) 287
127.0.0.1:6379> persist cloudsimplify:user:100:token
(integer) 1
127.0.0.1:6379> ttl cloudsimplify:user:100:token
(integer) -1

Key Spaces

• Key Spaces in Redis: These are similar to database namespaces or schemas.
  • You can have the same key name in different key spaces.
  • You can manage keys separately in each key space.
  • Key spaces are indexed starting from 0.
  • Use the command select [index] to choose a key space.
  • This allows you to select, get, and control different parts of the database independently.

❯ Select key space

❯ Syntax: select [index]

127.0.0.1:6379> set name cloudsimplify
OK
127.0.0.1:6379> get name
"cloudsimplify"
127.0.0.1:6379> select 1
OK
127.0.0.1:6379[1]> get name                 # You're now in key space index #1
(nil)
127.0.0.1:6379[1]> set name github
OK
127.0.0.1:6379[1]> get name
"github"
127.0.0.1:6379[1]> select 0
OK
127.0.0.1:6379> get name
"cloudsimplify"

Key Patterns Matching

• Key Patterns:
  • h?llo matches hello, hallo, and hxllo.
  • h*llo matches hllo and heeeello.
  • h[ae]llo matches hello and hallo, but not hillo.
  • h[^e]llo matches hallo, hbllo, etc., but not hello.
  • h[a-b]llo matches hallo and hbllo.
• Performance:
  • Redis can scan a database with 1 million keys in 40 milliseconds on an entry-level laptop.
• Usage Considerations:
  • Use the KEYS command with extreme care in production environments, as it can severely impact performance when used on large databases.
  • Consider using the SCAN command as an alternative.

❯ Get all available keys

❯ Syntax: keys *

127.0.0.1:6379> set hello 1
OK
127.0.0.1:6379> set hillo 2
OK
127.0.0.1:6379> set hallo 3
OK
127.0.0.1:6379> set hbllo 4
OK
127.0.0.1:6379> set hllo 5
OK
127.0.0.1:6379> set heeello 6
OK
127.0.0.1:6379> keys *
1) "hillo"
2) "hllo"
3) "hallo"
4) "hbllo"
5) "hello"
6) "heeello"
127.0.0.1:6379> keys h?llo
1) "hillo"
2) "hallo"
3) "hbllo"
4) "hello"
127.0.0.1:6379> keys * h*llo
(error) ERR wrong number of arguments for 'keys' command
127.0.0.1:6379> keys h*llo
1) "hillo"
2) "hllo"
3) "hallo"
4) "hbllo"
5) "hello"
6) "heeello"
127.0.0.1:6379> keys h[ae]llo
1) "hallo"
2) "hello"
127.0.0.1:6379> keys h[^e]llo
1) "hillo"
2) "hallo"
3) "hbllo"
127.0.0.1:6379> keys h[a-b]llo
1) "hallo"
2) "hbllo"

❯ Renames a key and overwrites the destination.

❯ Syntax: rename [key] [newkey]

127.0.0.1:6379> set fname cloudsimplify
OK
127.0.0.1:6379> set lname me
OK
127.0.0.1:6379> rename fname newfname
OK
127.0.0.1:6379> get fname
(nil)
127.0.0.1:6379> get newfname
"cloudsimplify"
127.0.0.1:6379> set fname github
OK
127.0.0.1:6379> get fname
"github"
127.0.0.1:6379> rename newfname fname # If newkey already exists it is overwritten, when this happens RENAME executes an implicit DEL operation
OK
127.0.0.1:6379> get fname             # fname is now overwritten to newfname value
"cloudsimplify"

❯ Renames a key only when the target key name doesn’t exist.

❯ Syntax: renamenx [key] [newkey]

127.0.0.1:6379> set fname cloudsimplify
OK
127.0.0.1:6379> set lname me
OK
127.0.0.1:6379> renamenx fname newfname
(integer) 1
127.0.0.1:6379> get fname
(nil)
127.0.0.1:6379> get newfname
"cloudsimplify"
127.0.0.1:6379> set fname github
OK
127.0.0.1:6379> renamenx newfname fname   # returns an error cause key fname exist
(integer) 0
127.0.0.1:6379> get fname
"github"

❯ Asynchronously deletes one or more keys

❯ Syntax: unlink [key...]

127.0.0.1:6379> set k1 v1
OK
127.0.0.1:6379> set k2 v2
OK
127.0.0.1:6379> set k3 v3
OK
127.0.0.1:6379> unlink k1 k2
(integer) 2
127.0.0.1:6379> get k1
(nil)
127.0.0.1:6379> get k2
(nil)
127.0.0.1:6379> get k3
"v3"

❯ Determines the type of value stored at a key

❯ Syntax: type [key]

127.0.0.1:6379> set k1 v1
OK
127.0.0.1:6379> lpush numbers 1 2 3 4 5
(integer) 5
127.0.0.1:6379> hset users fname cloudsimplify lname me
(integer) 2
127.0.0.1:6379> sadd cars mazda bmw audi
(integer) 3
127.0.0.1:6379> type k1
string
127.0.0.1:6379> type users
hash
127.0.0.1:6379> type numbers
list
127.0.0.1:6379> type cars
set