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Hash

Redis hashes are record types structured as collections of field-value pairs. You can use hashes to represent basic objects and to store groupings of counters, among other things.

Key Characteristics of Redis Hashes:

Field-Value Storage: Each hash can store multiple fields and values, similar to columns in a relational database.

Efficient Operations: You can read or write specific fields within a hash without retrieving or updating the entire hash.

Compact Storage: Hashes are memory-efficient, especially for storing objects with many fields.

• HSET sets the value of one or more fields on a hash.

• HGET returns the value at a given field.

• HMGET returns the values at one or more given fields.

• HINCRBY increments the value at a given field by the integer provided.

HSET "product:501" title "Laptop" price "799" description "Latest model..." stock "150"

(Retrieve title and price for the product)
HMGET "product:501" title price stock

(Decrement stock by 1 when a product is purchased)
HINCRBY "product:501" stock -1 

HMGET "product:501" title price stock

HGETALL "product:501"

HEXISTS "product:501" title

HDEL "product:501" "stock"

Use Case: User Session Store

HSET usersession:1 userid 1 name Rachel ip 10.20.133.233 hits 1

# One Value
HGET usersession:1 hits

# Multiple Values
HMGET usersession:1 userid name ip hits

# Increment
HINCRBY usersession:1 hits 1

HDEL usersession:1 hits

# What happens when you GET the deleted key?

HMGET usersession:1 userid name ip hits

EXPIRE

Sets a Key's time to live (TTL). The key will be automatically deleted from Redis once a specific duration (in seconds) has elapsed.

EXPIRE usersession:1 10

DEL

Immediately deletes a key and its associated value from Redis

DEL usersession:1

#hashVer 5.5.3