Redis Hash commands: HSET, HGET, HMGET, HDEL, HGETALL

Working with Hashes

A Hash stores multiple field-value pairs under one key. It is the natural fit for objects like users, products, or config records.

Writing and reading fields

# Set multiple fields at once (Redis 4+)
HSET user:42 name "Alice" age 30 email "alice@example.com"

# Read one field
HGET user:42 name        # → "Alice"

# Read multiple fields
HMGET user:42 name email # → ["Alice", "alice@example.com"]

# Read all fields
HGETALL user:42
# → { name: Alice, age: 30, email: alice@example.com }

Checking and deleting

HEXISTS user:42 phone   # → 0 (field absent)
HDEL user:42 email      # removes the email field
HLEN user:42            # → 2 (fields remaining)

Numeric fields

HINCRBY user:42 age 1   # increments age atomically → 31

Hash vs multiple Strings

Storing user:42:name, user:42:age as separate String keys works but wastes memory due to per-key overhead. A Hash collapses all fields under one key and uses a compact encoding (ziplist) for small hashes, saving significant memory. Use Hashes when an object has multiple attributes you read together.