HSETNX - Upstash Documentation

Use HSETNX to set a hash field only when it does not already exist.

The reply is 1 when the field was created and 0 when it was already present and left untouched. The check and the write happen atomically, so of several clients racing to fill the same field exactly one succeeds, which makes the command a way to claim a slot inside a hash without overwriting whatever a concurrent writer put there.

Syntax#

HSETNX <key> <field> <value>

Arguments#

Argument	Required	Repeatable	Description
`<key>`	Yes	No	Redis key targeted by the command.
`<field>`	Yes	No	Hash field name.
`<value>`	Yes	No	Value to store in the field.

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	Integer: `1` if the field was set, `0` if it already exists
RESP3	Integer: `1` if the field was set, `0` if it already exists

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

HSETNX my-key field value

@upstash/redis

import { Redis } from "@upstash/redis";const redis = Redis.fromEnv();await redis.hsetnx("key", "id", 1)

upstash_redis

from upstash_redis import Redisredis = Redis.from_env()result = redis.hsetnx("my-key", "field", "value")print(result)

ioredis

import Redis from "ioredis";const redis = new Redis(process.env.REDIS_URL!);const result = await redis.hsetnx("my-key", "field", "value");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.hSetNX("my-key", "field", "value");console.log(result);

redis-py

import osimport redisclient = redis.from_url(os.environ["REDIS_URL"])result = client.hsetnx("my-key", "field", "value")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.HSetNX(context.Background(), "my-key", "field", "value").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.hsetnx("my-key", "field", "value");  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 result = connection.hset_nx("my-key", "field", "value")?;    println!("{result:?}");    Ok(())}