Sorted Sets

Sorted set commands for storing unique elements with scores, ordered by score.

Commands

Command	Syntax	Description
ZADD	ZADD key score member [score member ...]	Add members with scores
ZREM	ZREM key member [member ...]	Remove members
ZSCORE	ZSCORE key member	Get member’s score
ZRANK	ZRANK key member	Get rank (ascending)
ZREVRANK	ZREVRANK key member	Get rank (descending)
ZCARD	ZCARD key	Count members
ZCOUNT	ZCOUNT key min max	Count by score range
ZRANGE	ZRANGE key start stop [WITHSCORES]	Get by rank range
ZREVRANGE	ZREVRANGE key start stop [WITHSCORES]	Get by rank (descending)
ZRANGEBYSCORE	ZRANGEBYSCORE key min max [WITHSCORES] [LIMIT offset count]	Get by score range
ZINCRBY	ZINCRBY key increment member	Increment member’s score
ZREMRANGEBYRANK	ZREMRANGEBYRANK key start stop	Remove by rank range
ZREMRANGEBYSCORE	ZREMRANGEBYSCORE key min max	Remove by score range

Examples

Basic Operations

# Add members with scores
127.0.0.1:6379> ZADD leaderboard 100 "alice" 85 "bob" 92 "charlie"
(integer) 3

# Get score
127.0.0.1:6379> ZSCORE leaderboard "alice"
"100"

# Get rank (0-indexed, ascending by score)
127.0.0.1:6379> ZRANK leaderboard "bob"
(integer) 0  # Lowest score

127.0.0.1:6379> ZREVRANK leaderboard "alice"
(integer) 0  # Highest score

Range Queries

# Get all by rank (ascending)
127.0.0.1:6379> ZRANGE leaderboard 0 -1
1) "bob"
2) "charlie"
3) "alice"

# With scores
127.0.0.1:6379> ZRANGE leaderboard 0 -1 WITHSCORES
1) "bob"
2) "85"
3) "charlie"
4) "92"
5) "alice"
6) "100"

# Top 3 (descending)
127.0.0.1:6379> ZREVRANGE leaderboard 0 2 WITHSCORES
1) "alice"
2) "100"
3) "charlie"
4) "92"
5) "bob"
6) "85"

Score Range Queries

# Get by score range
127.0.0.1:6379> ZRANGEBYSCORE leaderboard 85 95
1) "bob"
2) "charlie"

# With limit (pagination)
127.0.0.1:6379> ZRANGEBYSCORE leaderboard -inf +inf LIMIT 0 2
1) "bob"
2) "charlie"

# Count in range
127.0.0.1:6379> ZCOUNT leaderboard 90 100
(integer) 2  # charlie and alice

Update Scores

# Increment score
127.0.0.1:6379> ZINCRBY leaderboard 5 "bob"
"90"  # New score

# Use negative increment to decrease
127.0.0.1:6379> ZINCRBY leaderboard -10 "alice"
"90"

Remove Members

# Remove specific members
127.0.0.1:6379> ZREM leaderboard "bob"
(integer) 1

# Remove by rank range (lowest 2)
127.0.0.1:6379> ZREMRANGEBYRANK leaderboard 0 1
(integer) 2

# Remove by score range
127.0.0.1:6379> ZREMRANGEBYSCORE leaderboard 0 50
(integer) 1

Library Mode (Rust)

use redlite::Db;

let db = Db::open("mydata.db")?;

// Add members
db.zadd("leaderboard", &[(100.0, b"alice"), (85.0, b"bob")])?;

// Get score
let score = db.zscore("leaderboard", b"alice")?;  // Option<f64>

// Get rank
let rank = db.zrank("leaderboard", b"alice")?;  // Option<i64>

// Range queries
let top10 = db.zrevrange("leaderboard", 0, 9, true)?;  // With scores

// Score range
let in_range = db.zrangebyscore("leaderboard", 80.0, 100.0)?;

// Increment
db.zincrby("leaderboard", 5.0, b"bob")?;

// Count in range
let count = db.zcount("leaderboard", 80.0, 100.0)?;

Use Cases

Leaderboards

ZADD game:leaderboard 1500 "player:1" 1200 "player:2" 1800 "player:3"

# Top 10 players
ZREVRANGE game:leaderboard 0 9 WITHSCORES

# Player's rank
ZREVRANK game:leaderboard "player:1"

# Update score after game
ZINCRBY game:leaderboard 50 "player:1"

Time-Based Feeds

# Score = Unix timestamp
ZADD feed:user:1 1704067200 "post:100"
ZADD feed:user:1 1704153600 "post:101"

# Get recent posts
ZREVRANGE feed:user:1 0 9

# Get posts from last hour
ZRANGEBYSCORE feed:user:1 (now-3600) (now)

Priority Queues

# Score = priority (lower = higher priority)
ZADD tasks 1 "urgent:task1"
ZADD tasks 5 "normal:task2"
ZADD tasks 10 "low:task3"

# Get highest priority task
ZRANGE tasks 0 0
ZREM tasks "urgent:task1"  # Process and remove

Rate Limiting

# Score = timestamp of request
ZADD ratelimit:user:1 1704067200000 "req:1"
ZADD ratelimit:user:1 1704067201000 "req:2"

# Remove old entries (older than 1 minute)
ZREMRANGEBYSCORE ratelimit:user:1 0 (now-60000)

# Check request count
ZCARD ratelimit:user:1