ZSCAN - Upstash Documentation

Use ZSCAN to iterate the members of a sorted set in batches instead of reading them all at once. Each call takes a cursor and returns the next cursor together with a batch of members and their scores. Start at cursor 0 and keep calling with the cursor from the previous reply until the server returns 0. MATCH filters member names with a glob-style pattern and COUNT hints at how much work each call should do. Filtering happens after a batch is read, so a call can come back empty while the cursor is still non-zero. Members present for the whole iteration are returned at least once, and members added or removed while it runs may or may not appear. When you want members in score order rather than in scan order, use ZRANGE.

Syntax

ZSCAN <key> <cursor> [MATCH <pattern>] [COUNT <count>]

Arguments

Argument	Required	Repeatable	Description
`<key>`	Yes	No	Redis key targeted by the command.
`<cursor>`	Yes	No	Cursor returned by the previous call; start at `0`.
`MATCH <pattern>`	No	No	Return only elements matching this glob-style pattern.
`COUNT <count>`	No	No	Hint for how much work each iteration should do.

Important points

This operation can inspect a large part of the database. Prefer cursor-based scans where possible and avoid unbounded use on hot paths.
The cursor is opaque. Start with 0 and continue until the server returns cursor 0; a single iteration may return no elements.
RESP2 represents floating-point reply values as bulk strings; RESP3 may use native double replies. Client libraries commonly decode either form to a language number.

Response

The reply reports the result of the operation. Error replies have the same shape in RESP2 and RESP3 and are surfaced as exceptions by the SDKs below.

Protocol	Reply
RESP2	Two-element array: cursor and flat member/score array
RESP3	Two-element array: cursor and flat member/score array

Client libraries often decode bulk strings, maps, sets, and numeric strings into language-native values. The table describes the Redis wire reply.

Examples

TCP examples use the TLS REDIS_URL from the Upstash console. REST examples use UPSTASH_REDIS_REST_URL and UPSTASH_REDIS_REST_TOKEN.

Redis CLI

ZSCAN my-key 0

@upstash/redis

import { Redis } from "@upstash/redis";

const redis = Redis.fromEnv();

await redis.zadd("key",
    { score: 1, member: "a" },
    { score: 2, member: "ab" },
    { score: 3, member: "b" },
    { score: 4, member: "c" },
    { score: 5, member: "d" },
)
const [newCursor, members] = await redis.zscan("key", 0, { match: "a*"});
console.log(newCursor); // likely `0` since this is a very small set
console.log(members); // ["a", "ab"]

upstash_redis

from upstash_redis import Redis

redis = Redis.from_env()
result = redis.zscan("my-key", 0)
print(result)

ioredis

import Redis from "ioredis";

const redis = new Redis(process.env.REDIS_URL!);
const result = await redis.zscan("my-key", "0");
console.log(result);

node-redis

import { createClient } from "redis";

const client = await createClient({ url: process.env.REDIS_URL })
  .on("error", console.error)
  .connect();
const result = await client.zScan("my-key", "0");
console.log(result);

redis-py

import os
import redis

client = redis.from_url(os.environ["REDIS_URL"])
result = client.zscan("my-key", 0)
print(result)

go-redis

package main

import (
    "context"
    "fmt"
    "os"

    "github.com/redis/go-redis/v9"
)

func main() {
    opts, err := redis.ParseURL(os.Getenv("REDIS_URL"))
    if err != nil {
        panic(err)
    }
    client := redis.NewClient(opts)
    result, _, err := client.ZScan(context.Background(), "my-key", 0, "*", 0).Result()
    if err != nil {
        panic(err)
    }
    fmt.Println(result)
}

jedis

import java.net.URI;

import redis.clients.jedis.Jedis;

try (Jedis jedis = new Jedis(new URI(System.getenv("REDIS_URL")))) {
  Object result = jedis.zscan("my-key", "0");
  System.out.println(result);
}

redis-rs

use redis::TypedCommands;

fn main() -> redis::RedisResult<()> {
    let url = std::env::var("REDIS_URL").expect("REDIS_URL is not set");
    let client = redis::Client::open(url)?;
    let mut connection = client.get_connection()?;

    let iter: redis::Iter<(String, f64)> = connection.zscan("my-key")?;
    for (member, score) in iter {
        println!("{member}: {score}");
    }
    Ok(())
}

​Syntax

​Arguments

​Important points

​Response

​Examples

Syntax

Arguments

Important points

Response

Examples