Redis Strings
Introduction to Redis strings
String command summary
(view reference, 26 commands)
Redis strings store sequences of bytes, including text, serialized objects, and binary arrays. As such, strings are the simplest type of value you can associate with a Redis key. They're often used for caching, but they support additional functionality that lets you implement counters and perform bitwise operations, too.
Since Redis keys are strings, when we use the string type as a value too, we are mapping a string to another string. The string data type is useful for a number of use cases, like caching HTML fragments or pages.
Foundational: Set and retrieve string values using SET and GET (overwrites existing values)
> SET bike:1 Deimos
OK
> GET bike:1
"Deimos"res1 = r.set("bike:1", "Deimos")
print(res1) # True
res2 = r.get("bike:1")
print(res2) # Deimos
"""
Code samples for String doc pages:
https://redis.io/docs/latest/develop/data-types/strings/
"""
import redis
r = redis.Redis(decode_responses=True)
res1 = r.set("bike:1", "Deimos")
print(res1) # True
res2 = r.get("bike:1")
print(res2) # Deimos
res3 = r.set("bike:1", "bike", nx=True)
print(res3) # None
print(r.get("bike:1")) # Deimos
res4 = r.set("bike:1", "bike", xx=True)
print(res4) # True
res5 = r.mset({"bike:1": "Deimos", "bike:2": "Ares", "bike:3": "Vanth"})
print(res5) # True
res6 = r.mget(["bike:1", "bike:2", "bike:3"])
print(res6) # ['Deimos', 'Ares', 'Vanth']
r.set("total_crashes", 0)
res7 = r.incr("total_crashes")
print(res7) # 1
res8 = r.incrby("total_crashes", 10)
print(res8) # 11
const res1 = await client.set("bike:1", "Deimos");
console.log(res1); // OK
const res2 = await client.get("bike:1");
console.log(res2); // Deimos
import assert from 'assert';
import { createClient } from 'redis';
const client = createClient();
await client.connect();
const res1 = await client.set("bike:1", "Deimos");
console.log(res1); // OK
const res2 = await client.get("bike:1");
console.log(res2); // Deimos
const res3 = await client.set("bike:1", "bike", {'NX': true});
console.log(res3); // null
console.log(await client.get("bike:1")); // Deimos
const res4 = await client.set("bike:1", "bike", {'XX': true});
console.log(res4); // OK
const res5 = await client.mSet([
["bike:1", "Deimos"],
["bike:2", "Ares"],
["bike:3", "Vanth"]
]);
console.log(res5); // OK
const res6 = await client.mGet(["bike:1", "bike:2", "bike:3"]);
console.log(res6); // ['Deimos', 'Ares', 'Vanth']
await client.set("total_crashes", 0);
const res7 = await client.incr("total_crashes");
console.log(res7); // 1
const res8 = await client.incrBy("total_crashes", 10);
console.log(res8); // 11
String res1 = jedis.set("bike:1", "Deimos");
System.out.println(res1); // OK
String res2 = jedis.get("bike:1");
System.out.println(res2); // Deimos
package io.redis.examples;
import redis.clients.jedis.UnifiedJedis;
import redis.clients.jedis.params.SetParams;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class StringExample {
public void run() {
try (UnifiedJedis jedis = new UnifiedJedis("redis://localhost:6379")) {
String res1 = jedis.set("bike:1", "Deimos");
System.out.println(res1); // OK
String res2 = jedis.get("bike:1");
System.out.println(res2); // Deimos
Long res3 = jedis.setnx("bike:1", "bike");
System.out.println(res3); // 0 (because key already exists)
System.out.println(jedis.get("bike:1")); // Deimos (value is unchanged)
String res4 = jedis.set("bike:1", "bike", SetParams.setParams().xx()); // set the value to "bike" if it
// already
// exists
System.out.println(res4); // OK
String res5 = jedis.mset("bike:1", "Deimos", "bike:2", "Ares", "bike:3", "Vanth");
System.out.println(res5); // OK
List<String> res6 = jedis.mget("bike:1", "bike:2", "bike:3");
System.out.println(res6); // [Deimos, Ares, Vanth]
jedis.set("total_crashes", "0");
Long res7 = jedis.incr("total_crashes");
System.out.println(res7); // 1
Long res8 = jedis.incrBy("total_crashes", 10);
System.out.println(res8); // 11
}
}
}
CompletableFuture<Void> setAndGet = asyncCommands.set("bike:1", "Deimos").thenCompose(v -> {
System.out.println(v); // >>> OK
return asyncCommands.get("bike:1");
})
.thenAccept(System.out::println) // >>> Deimos
.toCompletableFuture();
package io.redis.examples.async;
import io.lettuce.core.*;
import io.lettuce.core.api.async.RedisAsyncCommands;
import io.lettuce.core.api.StatefulRedisConnection;
import java.util.*;
import java.util.concurrent.CompletableFuture;
public class StringExample {
public void run() {
RedisClient redisClient = RedisClient.create("redis://localhost:6379");
try (StatefulRedisConnection<String, String> connection = redisClient.connect()) {
RedisAsyncCommands<String, String> asyncCommands = connection.async();
CompletableFuture<Void> setAndGet = asyncCommands.set("bike:1", "Deimos").thenCompose(v -> {
System.out.println(v); // >>> OK
return asyncCommands.get("bike:1");
})
.thenAccept(System.out::println) // >>> Deimos
.toCompletableFuture();
setAndGet.join();
CompletableFuture<Void> setnx = asyncCommands.setnx("bike:1", "bike").thenCompose(v -> {
System.out.println(v); // >>> false (because key already exists)
return asyncCommands.get("bike:1");
})
.thenAccept(System.out::println) // >>> Deimos (value is unchanged)
.toCompletableFuture();
setnx.join();
// set the value to "bike" if it already exists
CompletableFuture<Void> setxx = asyncCommands.set("bike:1", "bike", SetArgs.Builder.xx())
.thenAccept(System.out::println) // >>> OK
.toCompletableFuture();
setxx.join();
Map<String, String> bikeMap = new HashMap<>();
bikeMap.put("bike:1", "Deimos");
bikeMap.put("bike:2", "Ares");
bikeMap.put("bike:3", "Vanth");
CompletableFuture<Void> mset = asyncCommands.mset(bikeMap).thenCompose(v -> {
System.out.println(v); // >>> OK
return asyncCommands.mget("bike:1", "bike:2", "bike:3");
})
.thenAccept(System.out::println)
// >>> [KeyValue[bike:1, Deimos], KeyValue[bike:2, Ares], KeyValue[bike:3,
// Vanth]]
.toCompletableFuture();
mset.join();
CompletableFuture<Void> incrby = asyncCommands.set("total_crashes", "0")
.thenCompose(v -> asyncCommands.incr("total_crashes")).thenCompose(v -> {
System.out.println(v); // >>> 1
return asyncCommands.incrby("total_crashes", 10);
})
.thenAccept(System.out::println) // >>> 11
.toCompletableFuture();
incrby.join();
} finally {
redisClient.shutdown();
}
}
}
Mono<Void> setAndGet = reactiveCommands.set("bike:1", "Deimos").doOnNext(v -> {
System.out.println(v); // OK
}).flatMap(v -> reactiveCommands.get("bike:1")).doOnNext(res -> {
System.out.println(res); // Deimos
}).then();
package io.redis.examples.reactive;
import io.lettuce.core.*;
import io.lettuce.core.api.reactive.RedisReactiveCommands;
import io.lettuce.core.api.StatefulRedisConnection;
import reactor.core.publisher.Mono;
import java.util.*;
public class StringExample {
public void run() {
RedisClient redisClient = RedisClient.create("redis://localhost:6379");
try (StatefulRedisConnection<String, String> connection = redisClient.connect()) {
RedisReactiveCommands<String, String> reactiveCommands = connection.reactive();
Mono<Void> setAndGet = reactiveCommands.set("bike:1", "Deimos").doOnNext(v -> {
System.out.println(v); // OK
}).flatMap(v -> reactiveCommands.get("bike:1")).doOnNext(res -> {
System.out.println(res); // Deimos
}).then();
Mono<Void> setnx = reactiveCommands.setnx("bike:1", "bike").doOnNext(v -> {
System.out.println(v); // false (because key already exists)
}).flatMap(v -> reactiveCommands.get("bike:1")).doOnNext(res -> {
System.out.println(res); // Deimos (value is unchanged)
}).then();
Mono<Void> setxx = reactiveCommands.set("bike:1", "bike", SetArgs.Builder.xx()).doOnNext(res -> {
System.out.println(res); // OK
}).then();
Map<String, String> bikeMap = new HashMap<>();
bikeMap.put("bike:1", "Deimos");
bikeMap.put("bike:2", "Ares");
bikeMap.put("bike:3", "Vanth");
Mono<Void> mset = reactiveCommands.mset(bikeMap).doOnNext(System.out::println) // OK
.flatMap(v -> reactiveCommands.mget("bike:1", "bike:2", "bike:3").collectList()).doOnNext(res -> {
System.out.println(res); // [KeyValue[bike:1, Deimos], KeyValue[bike:2, Ares], KeyValue[bike:3, Vanth]]
}).then();
Mono<Void> incrby = reactiveCommands.set("total_crashes", "0").flatMap(v -> reactiveCommands.incr("total_crashes"))
.doOnNext(v -> {
System.out.println(v); // 1
}).flatMap(v -> reactiveCommands.incrby("total_crashes", 10)).doOnNext(res -> {
System.out.println(res); // 11
}).then();
Mono.when(setAndGet, setnx, setxx, mset, incrby).block();
} finally {
redisClient.shutdown();
}
}
}
res1, err := rdb.Set(ctx, "bike:1", "Deimos", 0).Result()
if err != nil {
panic(err)
}
fmt.Println(res1) // >>> OK
res2, err := rdb.Get(ctx, "bike:1").Result()
if err != nil {
panic(err)
}
fmt.Println(res2) // >>> Deimos
package example_commands_test
import (
"context"
"fmt"
"github.com/redis/go-redis/v9"
)
func ExampleClient_set_get() {
ctx := context.Background()
rdb := redis.NewClient(&redis.Options{
Addr: "localhost:6379",
Password: "", // no password docs
DB: 0, // use default DB
})
res1, err := rdb.Set(ctx, "bike:1", "Deimos", 0).Result()
if err != nil {
panic(err)
}
fmt.Println(res1) // >>> OK
res2, err := rdb.Get(ctx, "bike:1").Result()
if err != nil {
panic(err)
}
fmt.Println(res2) // >>> Deimos
}
func ExampleClient_setnx_xx() {
ctx := context.Background()
rdb := redis.NewClient(&redis.Options{
Addr: "localhost:6379",
Password: "", // no password docs
DB: 0, // use default DB
})
res3, err := rdb.SetNX(ctx, "bike:1", "bike", 0).Result()
if err != nil {
panic(err)
}
fmt.Println(res3) // >>> false
res4, err := rdb.Get(ctx, "bike:1").Result()
if err != nil {
panic(err)
}
fmt.Println(res4) // >>> Deimos
res5, err := rdb.SetXX(ctx, "bike:1", "bike", 0).Result()
if err != nil {
panic(err)
}
fmt.Println(res5) // >>> OK
}
func ExampleClient_mset() {
ctx := context.Background()
rdb := redis.NewClient(&redis.Options{
Addr: "localhost:6379",
Password: "", // no password docs
DB: 0, // use default DB
})
res6, err := rdb.MSet(ctx, "bike:1", "Deimos", "bike:2", "Ares", "bike:3", "Vanth").Result()
if err != nil {
panic(err)
}
fmt.Println(res6) // >>> OK
res7, err := rdb.MGet(ctx, "bike:1", "bike:2", "bike:3").Result()
if err != nil {
panic(err)
}
fmt.Println(res7) // >>> [Deimos Ares Vanth]
}
func ExampleClient_incr() {
ctx := context.Background()
rdb := redis.NewClient(&redis.Options{
Addr: "localhost:6379",
Password: "", // no password docs
DB: 0, // use default DB
})
res8, err := rdb.Set(ctx, "total_crashes", "0", 0).Result()
if err != nil {
panic(err)
}
fmt.Println(res8) // >>> OK
res9, err := rdb.Incr(ctx, "total_crashes").Result()
if err != nil {
panic(err)
}
fmt.Println(res9) // >>> 1
res10, err := rdb.IncrBy(ctx, "total_crashes", 10).Result()
if err != nil {
panic(err)
}
fmt.Println(res10) // >>> 11
}
var res1 = db.StringSet("bike:1", "Deimos");
Console.WriteLine(res1); // true
var res2 = db.StringGet("bike:1");
Console.WriteLine(res2); // Deimos
public class StringSnippets
{
public void Run()
{
var muxer = ConnectionMultiplexer.Connect("localhost:6379");
var db = muxer.GetDatabase();
var res1 = db.StringSet("bike:1", "Deimos");
Console.WriteLine(res1); // true
var res2 = db.StringGet("bike:1");
Console.WriteLine(res2); // Deimos
var res3 = db.StringSet("bike:1", "bike", when: When.NotExists);
Console.WriteLine(res3); // false
Console.WriteLine(db.StringGet("bike:1"));
var res4 = db.StringSet("bike:1", "bike", when: When.Exists);
Console.WriteLine(res4); // true
var res5 = db.StringSet([
new ("bike:1", "Deimos"), new("bike:2", "Ares"), new("bike:3", "Vanth")
]);
Console.WriteLine(res5);
var res6 = db.StringGet(["bike:1", "bike:2", "bike:3"]);
Console.WriteLine(string.Join(", ", res6));
db.StringSet("total_crashes", 0);
var res7 = db.StringIncrement("total_crashes");
Console.WriteLine(res7); // 1
var res8 = db.StringIncrement("total_crashes", 10);
Console.WriteLine(res8);
}
} $res1 = $r->set('bike:1', 'Deimos');
echo "$res1" . PHP_EOL;
// >>> OK
$res2 = $r->get('bike:1');
echo "$res2" . PHP_EOL;
// >>> Deimos
<?php
require 'vendor/autoload.php';
use Predis\Client as PredisClient;
class DtStringTest
{
public function testDtString() {
$r = new PredisClient([
'scheme' => 'tcp',
'host' => '127.0.0.1',
'port' => 6379,
'password' => '',
'database' => 0,
]);
$res1 = $r->set('bike:1', 'Deimos');
echo "$res1" . PHP_EOL;
// >>> OK
$res2 = $r->get('bike:1');
echo "$res2" . PHP_EOL;
// >>> Deimos
$res3 = $r->set('bike:1', 'bike', 'nx');
echo "$res3" . PHP_EOL;
// >>> (null)
echo $r->get('bike:1') . PHP_EOL;
// >>> Deimos
$res4 = $r->set('bike:1', 'bike', 'xx');
echo "$res4" . PHP_EOL;
// >>> OK
$res5 = $r->mset([
'bike:1' => 'Deimos', 'bike:2' => 'Ares', 'bike:3' => 'Vanth'
]);
echo "$res5" . PHP_EOL;
// >>> OK
$res6 = $r->mget(['bike:1', 'bike:2', 'bike:3']);
echo json_encode($res6) . PHP_EOL;
// >>> ["Deimos","Ares","Vanth"]
$r->set('total_crashes', 0);
$res7 = $r->incr('total_crashes');
echo "$res7" . PHP_EOL;
// >>> 1
$res8 = $r->incrby('total_crashes', 10);
echo "$res8" . PHP_EOL;
// >>> 11
}
}res1 = r.set('bike:1', 'Deimos')
puts res1 # OK
res2 = r.get('bike:1')
puts res2 # Deimos
require 'redis'
r = Redis.new
res1 = r.set('bike:1', 'Deimos')
puts res1 # OK
res2 = r.get('bike:1')
puts res2 # Deimos
res3 = r.set('bike:1', 'bike', nx: true)
puts res3 # false
puts r.get('bike:1') # Deimos
res4 = r.set('bike:1', 'bike', xx: true)
puts res4 # true
res5 = r.mset('bike:1', 'Deimos', 'bike:2', 'Ares', 'bike:3', 'Vanth')
puts res5 # OK
res6 = r.mget('bike:1', 'bike:2', 'bike:3')
puts res6.inspect # ["Deimos", "Ares", "Vanth"]
r.set('total_crashes', 0)
res7 = r.incr('total_crashes')
puts res7 # 1
res8 = r.incrby('total_crashes', 10)
puts res8 # 11
if let Ok(res) = r.set("bike:1", "Deimos") {
let res: String = res;
println!("{res}"); // >>> OK
}
match r.get("bike:1") {
Ok(res) => {
let res: String = res;
println!("{res}"); // >>> Deimos
},
Err(e) => {
println!("Error getting bike:1: {e}");
return;
}
};
mod strings_tests {
use redis::{Commands, ExistenceCheck};
fn run() {
let mut r = match redis::Client::open("redis://127.0.0.1") {
Ok(client) => {
match client.get_connection() {
Ok(conn) => conn,
Err(e) => {
println!("Failed to connect to Redis: {e}");
return;
}
}
},
Err(e) => {
println!("Failed to create Redis client: {e}");
return;
}
};
if let Ok(res) = r.set("bike:1", "Deimos") {
let res: String = res;
println!("{res}"); // >>> OK
}
match r.get("bike:1") {
Ok(res) => {
let res: String = res;
println!("{res}"); // >>> Deimos
},
Err(e) => {
println!("Error getting bike:1: {e}");
return;
}
};
if let Ok(res) = r.set_options("bike:1", "bike", redis::SetOptions::default().conditional_set(ExistenceCheck::NX)) {
let res: bool = res;
println!("{res}"); // >>> false
}
match r.get("bike:1") {
Ok(res) => {
let res: String = res;
println!("{res}"); // >>> Deimos
},
Err(e) => {
println!("Error getting bike:1: {e}");
return;
}
};
if let Ok(res) = r.set_options("bike:1", "bike", redis::SetOptions::default().conditional_set(ExistenceCheck::XX)) {
let res: String = res;
println!("{res}"); // >>> OK
}
match r.get("bike:1") {
Ok(res) => {
let res: String = res;
println!("{res}"); // >>> bike
},
Err(e) => {
println!("Error getting bike:1: {e}");
return;
}
};
if let Ok(res) = r.mset(&[("bike:1", "Deimos"), ("bike:2", "Ares"), ("bike:3", "Vanth")]) {
let res: String = res;
println!("{res}"); // >>> OK
}
match r.mget(&["bike:1", "bike:2", "bike:3"]) {
Ok(res) => {
let res: Vec<String> = res;
println!("{res:?}"); // >>> ["Deimos", "Ares", "Vanth"]
},
Err(e) => {
println!("Error getting values: {e}");
return;
}
};
if let Ok(res) = r.set("total_crashes", 0) {
let res: String = res;
println!("{res}"); // >>> OK
}
if let Ok(res) = r.incr("total_crashes", 1) {
let res: i32 = res;
println!("{res}"); // >>> 1
}
if let Ok(res) = r.incr("total_crashes", 10) {
let res: i32 = res;
println!("{res}"); // >>> 11
}
}
} if let Ok(res) = r.set("bike:1", "Deimos").await {
let res: String = res;
println!("{res}"); // >>> OK
}
match r.get("bike:1").await {
Ok(res) => {
let res: String = res;
println!("{res}"); // >>> Deimos
},
Err(e) => {
println!("Error getting foo: {e}");
return;
}
};
mod tests {
use redis::{AsyncCommands, ExistenceCheck};
async fn run() {
let mut r = match redis::Client::open("redis://127.0.0.1") {
Ok(client) => {
match client.get_multiplexed_async_connection().await {
Ok(conn) => conn,
Err(e) => {
println!("Failed to connect to Redis: {e}");
return;
}
}
},
Err(e) => {
println!("Failed to create Redis client: {e}");
return;
}
};
if let Ok(res) = r.set("bike:1", "Deimos").await {
let res: String = res;
println!("{res}"); // >>> OK
}
match r.get("bike:1").await {
Ok(res) => {
let res: String = res;
println!("{res}"); // >>> Deimos
},
Err(e) => {
println!("Error getting foo: {e}");
return;
}
};
if let Ok(res) = r.set_options("bike:1", "bike", redis::SetOptions::default().conditional_set(ExistenceCheck::NX)).await {
let res: bool = res;
println!("{res}"); // >>> false
}
match r.get("bike:1").await {
Ok(res) => {
let res: String = res;
println!("{res}"); // >>> Deimos
},
Err(e) => {
println!("Error getting foo: {e}");
return;
}
};
if let Ok(res) = r.set_options("bike:1", "bike", redis::SetOptions::default().conditional_set(ExistenceCheck::XX)).await {
let res: String = res;
println!("{res}"); // >>> OK
}
match r.get("bike:1").await {
Ok(res) => {
let res: String = res;
println!("{res}"); // >>> bike
},
Err(e) => {
println!("Error getting foo: {e}");
return;
}
};
if let Ok(res) = r.mset(&[("bike:1", "Deimos"), ("bike:2", "Ares"), ("bike:3", "Vanth")]).await {
let res: String = res;
println!("{res}"); // >>> OK
}
match r.mget(&["bike:1", "bike:2", "bike:3"]).await {
Ok(res) => {
let res: Vec<String> = res;
println!("{res:?}"); // >>> ["Deimos", "Ares", "Vanth"]
},
Err(e) => {
println!("Error getting foo: {e}");
return;
}
};
if let Ok(res) = r.set("total_crashes", 0).await {
let res: String = res;
println!("{res}"); // >>> OK
}
if let Ok(res) = r.incr("total_crashes", 1).await {
let res: i32 = res;
println!("{res}"); // >>> 1
}
if let Ok(res) = r.incr("total_crashes", 10).await {
let res: i32 = res;
println!("{res}"); // >>> 11
}
}
}As you can see using the SET and the GET commands are the way we set
and retrieve a string value. Note that SET will replace any existing value
already stored into the key, in the case that the key already exists, even if
the key is associated with a non-string value. So SET performs an assignment.
Values can be strings (including binary data) of every kind, for instance you can store a jpeg image inside a value. A value can't be bigger than 512 MB.
The SET command has interesting options that are provided as additional
arguments. For example, I may ask SET to fail if the key already exists,
or the opposite, that it only succeed if the key already exists:
Conditional SET operations: Use NX and XX options to control key existence when you need atomic compare-and-set behavior
> SET bike:1 bike NX
(nil)
> SET bike:1 bike XX
OKres3 = r.set("bike:1", "bike", nx=True)
print(res3) # None
print(r.get("bike:1")) # Deimos
res4 = r.set("bike:1", "bike", xx=True)
print(res4) # True
const res3 = await client.set("bike:1", "bike", {'NX': true});
console.log(res3); // null
console.log(await client.get("bike:1")); // Deimos
const res4 = await client.set("bike:1", "bike", {'XX': true});
console.log(res4); // OK
Long res3 = jedis.setnx("bike:1", "bike");
System.out.println(res3); // 0 (because key already exists)
System.out.println(jedis.get("bike:1")); // Deimos (value is unchanged)
String res4 = jedis.set("bike:1", "bike", SetParams.setParams().xx()); // set the value to "bike" if it
// already
// exists
System.out.println(res4); // OK
CompletableFuture<Void> setnx = asyncCommands.setnx("bike:1", "bike").thenCompose(v -> {
System.out.println(v); // >>> false (because key already exists)
return asyncCommands.get("bike:1");
})
.thenAccept(System.out::println) // >>> Deimos (value is unchanged)
.toCompletableFuture();
setnx.join();
// set the value to "bike" if it already exists
CompletableFuture<Void> setxx = asyncCommands.set("bike:1", "bike", SetArgs.Builder.xx())
.thenAccept(System.out::println) // >>> OK
.toCompletableFuture();
setxx.join();
Mono<Void> setnx = reactiveCommands.setnx("bike:1", "bike").doOnNext(v -> {
System.out.println(v); // false (because key already exists)
}).flatMap(v -> reactiveCommands.get("bike:1")).doOnNext(res -> {
System.out.println(res); // Deimos (value is unchanged)
}).then();
Mono<Void> setxx = reactiveCommands.set("bike:1", "bike", SetArgs.Builder.xx()).doOnNext(res -> {
System.out.println(res); // OK
}).then();
res3, err := rdb.SetNX(ctx, "bike:1", "bike", 0).Result()
if err != nil {
panic(err)
}
fmt.Println(res3) // >>> false
res4, err := rdb.Get(ctx, "bike:1").Result()
if err != nil {
panic(err)
}
fmt.Println(res4) // >>> Deimos
res5, err := rdb.SetXX(ctx, "bike:1", "bike", 0).Result()
if err != nil {
panic(err)
}
fmt.Println(res5) // >>> OK
var res3 = db.StringSet("bike:1", "bike", when: When.NotExists);
Console.WriteLine(res3); // false
Console.WriteLine(db.StringGet("bike:1"));
var res4 = db.StringSet("bike:1", "bike", when: When.Exists);
Console.WriteLine(res4); // true
$res3 = $r->set('bike:1', 'bike', 'nx');
echo "$res3" . PHP_EOL;
// >>> (null)
echo $r->get('bike:1') . PHP_EOL;
// >>> Deimos
$res4 = $r->set('bike:1', 'bike', 'xx');
echo "$res4" . PHP_EOL;
// >>> OK
res3 = r.set('bike:1', 'bike', nx: true)
puts res3 # false
puts r.get('bike:1') # Deimos
res4 = r.set('bike:1', 'bike', xx: true)
puts res4 # true
if let Ok(res) = r.set_options("bike:1", "bike", redis::SetOptions::default().conditional_set(ExistenceCheck::NX)) {
let res: bool = res;
println!("{res}"); // >>> false
}
match r.get("bike:1") {
Ok(res) => {
let res: String = res;
println!("{res}"); // >>> Deimos
},
Err(e) => {
println!("Error getting bike:1: {e}");
return;
}
};
if let Ok(res) = r.set_options("bike:1", "bike", redis::SetOptions::default().conditional_set(ExistenceCheck::XX)) {
let res: String = res;
println!("{res}"); // >>> OK
}
match r.get("bike:1") {
Ok(res) => {
let res: String = res;
println!("{res}"); // >>> bike
},
Err(e) => {
println!("Error getting bike:1: {e}");
return;
}
};
if let Ok(res) = r.set_options("bike:1", "bike", redis::SetOptions::default().conditional_set(ExistenceCheck::NX)).await {
let res: bool = res;
println!("{res}"); // >>> false
}
match r.get("bike:1").await {
Ok(res) => {
let res: String = res;
println!("{res}"); // >>> Deimos
},
Err(e) => {
println!("Error getting foo: {e}");
return;
}
};
if let Ok(res) = r.set_options("bike:1", "bike", redis::SetOptions::default().conditional_set(ExistenceCheck::XX)).await {
let res: String = res;
println!("{res}"); // >>> OK
}
match r.get("bike:1").await {
Ok(res) => {
let res: String = res;
println!("{res}"); // >>> bike
},
Err(e) => {
println!("Error getting foo: {e}");
return;
}
};
There are a number of other commands for operating on strings. For example
the GETSET command sets a key to a new value, returning the old value as the
result. You can use this command, for example, if you have a
system that increments a Redis key using INCR
every time your web site receives a new visitor. You may want to collect this
information once every hour, without losing a single increment.
You can GETSET the key, assigning it the new value of "0" and reading the
old value back.
The ability to set or retrieve the value of multiple keys in a single
command is also useful for reduced latency. For this reason there are
the MSET and MGET commands:
Set and retrieve multiple values using MSET and MGET when you need to reduce round trips to the server
> MSET bike:1 "Deimos" bike:2 "Ares" bike:3 "Vanth"
OK
> MGET bike:1 bike:2 bike:3
1) "Deimos"
2) "Ares"
3) "Vanth"res5 = r.mset({"bike:1": "Deimos", "bike:2": "Ares", "bike:3": "Vanth"})
print(res5) # True
res6 = r.mget(["bike:1", "bike:2", "bike:3"])
print(res6) # ['Deimos', 'Ares', 'Vanth']
const res5 = await client.mSet([
["bike:1", "Deimos"],
["bike:2", "Ares"],
["bike:3", "Vanth"]
]);
console.log(res5); // OK
const res6 = await client.mGet(["bike:1", "bike:2", "bike:3"]);
console.log(res6); // ['Deimos', 'Ares', 'Vanth']
String res5 = jedis.mset("bike:1", "Deimos", "bike:2", "Ares", "bike:3", "Vanth");
System.out.println(res5); // OK
List<String> res6 = jedis.mget("bike:1", "bike:2", "bike:3");
System.out.println(res6); // [Deimos, Ares, Vanth]
Map<String, String> bikeMap = new HashMap<>();
bikeMap.put("bike:1", "Deimos");
bikeMap.put("bike:2", "Ares");
bikeMap.put("bike:3", "Vanth");
CompletableFuture<Void> mset = asyncCommands.mset(bikeMap).thenCompose(v -> {
System.out.println(v); // >>> OK
return asyncCommands.mget("bike:1", "bike:2", "bike:3");
})
.thenAccept(System.out::println)
// >>> [KeyValue[bike:1, Deimos], KeyValue[bike:2, Ares], KeyValue[bike:3,
// Vanth]]
.toCompletableFuture();
Map<String, String> bikeMap = new HashMap<>();
bikeMap.put("bike:1", "Deimos");
bikeMap.put("bike:2", "Ares");
bikeMap.put("bike:3", "Vanth");
Mono<Void> mset = reactiveCommands.mset(bikeMap).doOnNext(System.out::println) // OK
.flatMap(v -> reactiveCommands.mget("bike:1", "bike:2", "bike:3").collectList()).doOnNext(res -> {
System.out.println(res); // [KeyValue[bike:1, Deimos], KeyValue[bike:2, Ares], KeyValue[bike:3, Vanth]]
}).then();
res6, err := rdb.MSet(ctx, "bike:1", "Deimos", "bike:2", "Ares", "bike:3", "Vanth").Result()
if err != nil {
panic(err)
}
fmt.Println(res6) // >>> OK
res7, err := rdb.MGet(ctx, "bike:1", "bike:2", "bike:3").Result()
if err != nil {
panic(err)
}
fmt.Println(res7) // >>> [Deimos Ares Vanth]
var res5 = db.StringSet([
new ("bike:1", "Deimos"), new("bike:2", "Ares"), new("bike:3", "Vanth")
]);
Console.WriteLine(res5);
var res6 = db.StringGet(["bike:1", "bike:2", "bike:3"]);
Console.WriteLine(string.Join(", ", res6));
$res5 = $r->mset([
'bike:1' => 'Deimos', 'bike:2' => 'Ares', 'bike:3' => 'Vanth'
]);
echo "$res5" . PHP_EOL;
// >>> OK
$res6 = $r->mget(['bike:1', 'bike:2', 'bike:3']);
echo json_encode($res6) . PHP_EOL;
// >>> ["Deimos","Ares","Vanth"]
res5 = r.mset('bike:1', 'Deimos', 'bike:2', 'Ares', 'bike:3', 'Vanth')
puts res5 # OK
res6 = r.mget('bike:1', 'bike:2', 'bike:3')
puts res6.inspect # ["Deimos", "Ares", "Vanth"]
if let Ok(res) = r.mset(&[("bike:1", "Deimos"), ("bike:2", "Ares"), ("bike:3", "Vanth")]) {
let res: String = res;
println!("{res}"); // >>> OK
}
match r.mget(&["bike:1", "bike:2", "bike:3"]) {
Ok(res) => {
let res: Vec<String> = res;
println!("{res:?}"); // >>> ["Deimos", "Ares", "Vanth"]
},
Err(e) => {
println!("Error getting values: {e}");
return;
}
};
if let Ok(res) = r.mset(&[("bike:1", "Deimos"), ("bike:2", "Ares"), ("bike:3", "Vanth")]).await {
let res: String = res;
println!("{res}"); // >>> OK
}
match r.mget(&["bike:1", "bike:2", "bike:3"]).await {
Ok(res) => {
let res: Vec<String> = res;
println!("{res:?}"); // >>> ["Deimos", "Ares", "Vanth"]
},
Err(e) => {
println!("Error getting foo: {e}");
return;
}
};
When MGET is used, Redis returns an array of values.
Strings as counters
Even if strings are the basic values of Redis, there are interesting operations you can perform with them. For instance, one is atomic increment:
Atomic counters: Increment string values using INCR and INCRBY when you need thread-safe operations (initializes to 0 if key doesn't exist)
> SET total_crashes 0
OK
> INCR total_crashes
(integer) 1
> INCRBY total_crashes 10
(integer) 11r.set("total_crashes", 0)
res7 = r.incr("total_crashes")
print(res7) # 1
res8 = r.incrby("total_crashes", 10)
print(res8) # 11
await client.set("total_crashes", 0);
const res7 = await client.incr("total_crashes");
console.log(res7); // 1
const res8 = await client.incrBy("total_crashes", 10);
console.log(res8); // 11
jedis.set("total_crashes", "0");
Long res7 = jedis.incr("total_crashes");
System.out.println(res7); // 1
Long res8 = jedis.incrBy("total_crashes", 10);
System.out.println(res8); // 11
CompletableFuture<Void> incrby = asyncCommands.set("total_crashes", "0")
.thenCompose(v -> asyncCommands.incr("total_crashes")).thenCompose(v -> {
System.out.println(v); // >>> 1
return asyncCommands.incrby("total_crashes", 10);
})
.thenAccept(System.out::println) // >>> 11
.toCompletableFuture();
Mono<Void> incrby = reactiveCommands.set("total_crashes", "0").flatMap(v -> reactiveCommands.incr("total_crashes"))
.doOnNext(v -> {
System.out.println(v); // 1
}).flatMap(v -> reactiveCommands.incrby("total_crashes", 10)).doOnNext(res -> {
System.out.println(res); // 11
}).then();
res8, err := rdb.Set(ctx, "total_crashes", "0", 0).Result()
if err != nil {
panic(err)
}
fmt.Println(res8) // >>> OK
res9, err := rdb.Incr(ctx, "total_crashes").Result()
if err != nil {
panic(err)
}
fmt.Println(res9) // >>> 1
res10, err := rdb.IncrBy(ctx, "total_crashes", 10).Result()
if err != nil {
panic(err)
}
fmt.Println(res10) // >>> 11
db.StringSet("total_crashes", 0);
var res7 = db.StringIncrement("total_crashes");
Console.WriteLine(res7); // 1
var res8 = db.StringIncrement("total_crashes", 10);
Console.WriteLine(res8);
$r->set('total_crashes', 0);
$res7 = $r->incr('total_crashes');
echo "$res7" . PHP_EOL;
// >>> 1
$res8 = $r->incrby('total_crashes', 10);
echo "$res8" . PHP_EOL;
// >>> 11
r.set('total_crashes', 0)
res7 = r.incr('total_crashes')
puts res7 # 1
res8 = r.incrby('total_crashes', 10)
puts res8 # 11
if let Ok(res) = r.set("total_crashes", 0) {
let res: String = res;
println!("{res}"); // >>> OK
}
if let Ok(res) = r.incr("total_crashes", 1) {
let res: i32 = res;
println!("{res}"); // >>> 1
}
if let Ok(res) = r.incr("total_crashes", 10) {
let res: i32 = res;
println!("{res}"); // >>> 11
}
if let Ok(res) = r.set("total_crashes", 0).await {
let res: String = res;
println!("{res}"); // >>> OK
}
if let Ok(res) = r.incr("total_crashes", 1).await {
let res: i32 = res;
println!("{res}"); // >>> 1
}
if let Ok(res) = r.incr("total_crashes", 10).await {
let res: i32 = res;
println!("{res}"); // >>> 11
}
The INCR command parses the string value as an integer,
increments it by one, and finally sets the obtained value as the new value.
There are other similar commands like INCRBY,
DECR and DECRBY. Internally it's
always the same command, acting in a slightly different way.
What does it mean that INCR is atomic? That even multiple clients issuing INCR against the same key will never enter into a race condition. For instance, it will never happen that client 1 reads "10", client 2 reads "10" at the same time, both increment to 11, and set the new value to 11. The final value will always be 12 and the read-increment-set operation is performed while all the other clients are not executing a command at the same time.
Limits
By default, a single Redis string can be a maximum of 512 MB.
Bitwise and bitfield operations
To perform bitwise operations on a string, see the bitmaps data type docs. To store and manipulate integer values within a string, see the bitfields data type docs.
Performance
Most string operations are O(1), which means they're highly efficient.
However, be careful with the SUBSTR, GETRANGE, and SETRANGE commands, which can be O(n).
These random-access string commands may cause performance issues when dealing with large strings.
Alternatives
If you're storing structured data as a serialized string, you may also want to consider Redis hashes or JSON.
Learn more
- Redis Strings Explained is a short, comprehensive video explainer on Redis strings.
- Redis University's RU101 covers Redis strings in detail.