> ## Documentation Index
> Fetch the complete documentation index at: https://upstash.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# HSCAN

> Incrementally iterate hash fields.

Use `HSCAN` to iterate the fields of a hash in batches instead of reading it all at once.

Each call takes a cursor and returns the next cursor together with a batch of field and value pairs. Start at cursor `0` and keep calling with the cursor from the previous reply until the server returns `0`, which ends the iteration. Because each call does a bounded amount of work, this avoids the long single reply that [`HGETALL`](/docs/redis/commands/hash/hgetall) produces on a large hash.

`MATCH` filters field names with a glob-style pattern, `COUNT` hints at how much work each call should do, and `NOVALUES` returns field names only, which is noticeably cheaper when values are large and you do not need them. Filtering is applied after a batch has been read, so a call can return nothing while the cursor is still non-zero: only a cursor of `0` means the iteration is over. Fields present for the whole iteration are returned at least once, and fields added or removed while it runs may or may not appear.

## Syntax

```redis theme={"system"}
HSCAN <key> <cursor> [MATCH <pattern>] [COUNT <count>] [NOVALUES]
```

## 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.       |
| `NOVALUES`        | No       | No         | Return only field names, without their values.         |

## 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.

## 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 field/value array, or field array with `NOVALUES` |
| RESP3    | Two-element array: cursor and flat field/value array, or field array with `NOVALUES` |

<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 theme={"system"}
    HSCAN my-key 0
    ```
  </Accordion>

  <Accordion title="@upstash/redis" icon="node-js" iconType="brands">
    ```ts theme={"system"}
    import { Redis } from "@upstash/redis";

    const redis = Redis.fromEnv();

    await redis.hset("key", {
      id: 1,
      username: "chronark",
      name: "andreas"
     });
    const [newCursor, fields] = await redis.hscan("key", 0);
    console.log(newCursor); // likely `0` since this is a very small hash
    console.log(fields); // ["id", 1, "username", "chronark", "name", "andreas"]
    ```
  </Accordion>

  <Accordion title="upstash_redis" icon="python" iconType="brands">
    ```python theme={"system"}
    from upstash_redis import Redis

    redis = Redis.from_env()
    result = redis.hscan("my-key", 0)
    print(result)
    ```
  </Accordion>

  <Accordion title="ioredis" icon="node-js" iconType="brands">
    ```ts theme={"system"}
    import Redis from "ioredis";

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

  <Accordion title="node-redis" icon="node-js" iconType="brands">
    ```ts theme={"system"}
    import { createClient } from "redis";

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

  <Accordion title="redis-py" icon="python" iconType="brands">
    ```python theme={"system"}
    import os
    import redis

    client = redis.from_url(os.environ["REDIS_URL"])
    result = client.hscan("my-key", 0)
    print(result)
    ```
  </Accordion>

  <Accordion title="go-redis" icon="golang" iconType="brands">
    ```go theme={"system"}
    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.HScan(context.Background(), "my-key", 0, "*", 0).Result()
        if err != nil {
            panic(err)
        }
        fmt.Println(result)
    }
    ```
  </Accordion>

  <Accordion title="jedis" icon="java" iconType="brands">
    ```java theme={"system"}
    import java.net.URI;

    import redis.clients.jedis.Jedis;

    try (Jedis jedis = new Jedis(new URI(System.getenv("REDIS_URL")))) {
      Object result = jedis.hscan("my-key", "0");
      System.out.println(result);
    }
    ```
  </Accordion>

  <Accordion title="redis-rs" icon="rust" iconType="brands">
    ```rust theme={"system"}
    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, String)> = connection.hscan("my-key")?;
        for (field, value) in iter {
            println!("{field}: {value}");
        }
        Ok(())
    }
    ```
  </Accordion>
</AccordionGroup>


## Related topics

- [HSCAN](/docs/redis/sdks/py/commands/hash/hscan.md)
- [HKEYS](/docs/redis/commands/hash/hkeys.md)
- [HVALS](/docs/redis/commands/hash/hvals.md)
- [HGETALL](/docs/redis/commands/hash/hgetall.md)