LPUSHX - Upstash Documentation

Use LPUSHX to add elements to the head of a list only when the list already exists.

Nothing happens and the reply is 0 when the key does not exist, and no key is created. This is the difference from LPUSH, and it is what you want when a list should only be fed while a consumer is holding it open, so that stale producers do not resurrect a queue that was already drained and deleted.

Syntax#

LPUSHX <key> <element> [<element> ...]

Arguments#

Argument	Required	Repeatable	Description
`<key>`	Yes	No	Redis key targeted by the command.
`<element>`	Yes	Yes	Element to push.

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
RESP3	Integer

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

LPUSHX my-key element

@upstash/redis

import { Redis } from "@upstash/redis";const redis = Redis.fromEnv();await redis.lpush("key", "a", "b", "c");const length = await redis.lpushx("key", "d");console.log(length); // 4

upstash_redis

from upstash_redis import Redisredis = Redis.from_env()result = redis.lpushx("my-key", "element")print(result)

ioredis

import Redis from "ioredis";const redis = new Redis(process.env.REDIS_URL!);const result = await redis.lpushx("my-key", "element");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.lPushX("my-key", "element");console.log(result);

redis-py

import osimport redisclient = redis.from_url(os.environ["REDIS_URL"])result = client.lpushx("my-key", "element")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.LPushX(context.Background(), "my-key", "element").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.lpushx("my-key", "element");  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.lpush_exists("my-key", "element")?;    println!("{result:?}");    Ok(())}