ARSCAN - Upstash Documentation

Use ARSCAN to list the occupied slots of an array in an index range.

Unlike ARGETRANGE, which returns a null for every hole, ARSCAN skips empty slots and pairs each value with its index, so the cost of the reply tracks the data actually stored rather than the width of the range. That is what makes it usable over a sparse array whose indexes are, for instance, timestamps.

Results come back in ascending index order. LIMIT caps how many slots are returned, so a scan over a wide range can be walked in pages by using the last index of one page as the start of the next.

See the array command overview for the data model these commands share.

Syntax#

ARSCAN <key> <start> <end> [LIMIT <limit>]

Arguments#

Argument	Required	Repeatable	Description
`<key>`	Yes	No	Array key targeted by the command.
`<start>`	Yes	No	First index of the range, inclusive.
`<end>`	Yes	No	Last index of the range, inclusive.
`LIMIT <limit>`	No	No	Maximum number of slots to return. Must be greater than `0`.

Important points#

Only occupied slots are returned, in ascending index order.
<start> must not be greater than <end>; unlike ARGETRANGE, ARSCAN does not reverse the range.

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	Array of two-element arrays, each an index and its value
RESP3	Array of two-element arrays, each an index and its value

Note

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

ARSCAN my-array 0 1000 LIMIT 10

@upstash/redis

Note

This command is not supported yet in @upstash/redis.

upstash_redis

Note

This command is not supported yet in upstash_redis.

ioredis

import Redis from "ioredis";const redis = new Redis(process.env.REDIS_URL!);const result = await redis.arscan("my-array", 0, 1000, "LIMIT", 10);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.arScan("my-array", 0, 1000, { LIMIT: 10 });console.log(result);

redis-py

import osimport redisclient = redis.from_url(os.environ["REDIS_URL"])result = client.arscan("my-array", 0, 1000, limit=10)print(result)

go-redis

package mainimport (    "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.ARScan(context.Background(), "my-array", 0, 1000, &redis.ARScanArgs{Limit: 10}).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.arscan("my-array", 0, 1000, 10);  System.out.println(result);}

redis-rs

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 mut command = redis::cmd("ARSCAN");    command.arg("my-array");    command.arg("0");    command.arg("1000");    command.arg("LIMIT");    command.arg("10");    let result: redis::Value = command.query(&mut connection)?;    println!("{result:?}");    Ok(())}