Hashes

Redis Hashes

A Redis hash is a map between string field names and string values. Hashes are perfect for representing objects — a user profile, product details, session data — while keeping everything in a single key.

HSET — Set Fields

HSET user:1 name "Alice" email "alice@example.com" age "30"

Returns the number of new fields added (not updated). Existing fields are updated silently.

HGET — Get a Single Field

HGET user:1 name
HGET user:1 email

Output:

"Alice"
"alice@example.com"

HGETALL — Get All Fields and Values

HGETALL user:1

Output (interleaved field/value pairs):

1) "name"
2) "Alice"
3) "email"
4) "alice@example.com"
5) "age"
6) "30"

HKEYS, HVALS, HLEN

HKEYS user:1     -- all field names
HVALS user:1     -- all field values
HLEN user:1      -- number of fields

HEXISTS — Check if Field Exists

HEXISTS user:1 name    -- 1 (exists)
HEXISTS user:1 phone   -- 0 (not found)

HDEL — Delete Fields

HDEL user:1 age

HMGET — Get Multiple Fields

HMGET user:1 name email phone

Output:

1) "Alice"
2) "alice@example.com"
3) (nil)

HINCRBY — Increment a Hash Field

HSET product:42 stock "100"
HINCRBY product:42 stock -3
HGET product:42 stock    -- "97"

Why Hashes?

Compared to storing a JSON string:

• Access individual fields without parsing the whole value
• Modify one field without rewriting the entire object
• Check if a field exists without loading all data

Your Task

Store a product in a hash product:1 with fields: name → "Laptop", price → "999", stock → "50". Then use HGETALL to verify.