# ZSCAN

> Incrementally iterate sorted set.

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`](/redis/commands/sorted-set/zrange).

## Syntax

```redis
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 |

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

## Examples

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

<AccordionGroup>

<Accordion title="Redis CLI" icon="terminal">

```bash
ZSCAN my-key 0
```

</Accordion>

<Accordion title="@upstash/redis" icon="node-js" iconType="brands">

```ts
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"]
```

</Accordion>

<Accordion title="upstash_redis" icon="python" iconType="brands">

```python
from upstash_redis import Redis

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

</Accordion>

<Accordion title="ioredis" icon="node-js" iconType="brands">

```ts
import Redis from "ioredis";

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

</Accordion>

<Accordion title="node-redis" icon="node-js" iconType="brands">

```ts
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);
```

</Accordion>

<Accordion title="redis-py" icon="python" iconType="brands">

```python
import os
import redis

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

</Accordion>

<Accordion title="go-redis" icon="golang" iconType="brands">

```go
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)
}
```

</Accordion>

<Accordion title="jedis" icon="java" iconType="brands">

```java
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);
}
```

</Accordion>

<Accordion title="redis-rs" icon="rust" iconType="brands">

```rust
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(())
}
```

</Accordion>

</AccordionGroup>