SPOP [set] [count] was introduced in Redis v3.2 - https://redis.io/commands/spop , my REDIS version is 2.7.
How can I atomically pop several items from a SET using cli commands?
Is it possible to do something like...?
MULTI
a = SPOP myset //It would be nice if I could store this in a variable?
b = SPOP myset
...
SREM a
SREM b
...
EXEC
//
Yes, MULTI combined with a sequence of SPOPs would return the results as part of the EXEC call:
each element being the reply to each of the commands in the atomic transaction
source: https://redis.io/commands/exec
MULTI
SPOP myset
SPOP myset
EXEC
As an alternative, you could also use a Lua script, with EVAL being introduced in Redis 2.6: this would allow you to use variables (hosted within the scope of the script itself, which is being run on the Redis process) and alike but may be more complex, possibly overkill for your scenario.
As a side note, SPOP is already removing items, so there is no need to SREM them.
I use jedis + lua to eval script, here is my lua script:
redis.replicate_commands()
local second = redis.call('TIME')[1]
local currentKey = KEYS[1]..second
if redis.call('EXISTS', currentKey) == 0 then
redis.call('SETEX', currentKey, 1, 1)
return 1
else
return redis.call('INCR', currentKey)
end
As I use 'Time', it reports error:Write commands not allowed after non deterministic commands.
after searching on internet, I add 'redis.replicate_commands()' as first line of lua script, but it still reports error:ERR Error running script (call to f_c89a6ee8ad732a325e530f4a69226851cde302e2): #user_script:1: user_script:1: attempt to call field 'replicate_commands' (a nil value)
Does replicate_commands need arguments or is there a way to solve my problem?
redis version:3.0
jedis version:2.9
lua version: I don't know where to find
The error attempt to call field 'replicate_commands' (a nil value) means replicate_commands() doesn't exists in the redis object. It is a Lua-side error message.
replicate_commands() was introduced until Redis 3.2. See EVAL - Replicating commands instead of scripts. Consider upgrading.
The first error message (Write commands not allowed after non deterministic commands) is a redis-side message, you cannot call write-commands (like SET, SETEX, INCR, etc) after calling non-deterministic commands (like SPOP, SCAN, RANDOMKEY, TIME, etc).
A very important part of scripting is writing scripts that are pure functions.
Scripts executed in a Redis instance are, by default, propagated to
replicas and to the AOF file by sending the script itself -- not the
resulting commands.
This is so if the Redis server is restarted, playing again the AOF log, or also if replicated in a slave, the script should deliver the same dataset.
This is why in Redis 3.2 replicate_commands() was introduced. And starting with Redis 5 scripts are always replicated as effects -- as if replicate_commands() was called when the script started. But for versions before 3.2, you simply cannot do this.
Therefore, either upgrade to 3.2 or later, or pass currentKey already calculated to the script from the client instead.
Note that creating currentKey dynamically makes your script single-instance-only.
All Redis commands must be analyzed before execution to determine
which keys the command will operate on. In order for this to be true
for EVAL, keys must be passed explicitly. This is useful in many ways,
but especially to make sure Redis Cluster can forward your request to
the appropriate cluster node.
Note this rule is not enforced in order to provide the user with
opportunities to abuse the Redis single instance configuration, at the
cost of writing scripts not compatible with Redis Cluster.
Finally, the Lua version at Redis 3.0.0 is Lua 5.1.5, same as all the way up to Redis 6 RC1.
Is it possible to have one Redis Lua script hit more than one database? I currently have information of one type in DB 0 and information of another type in DB 1. My normal workflow is doing updates on DB 1 based on an API call along with meta information from DB 0. I'd love to do everything in one Lua script, but can't figure out how to hit multiple dbs. I'm doing this in Python using redis-py:
lua_script(keys=some_keys,
args=some_args,
client=some_client)
Since the client implies a specific db, I'm stuck. Ideas?
It is usually a wrong idea to put related data in different Redis databases. There is almost no benefit compared to defining namespaces by key naming conventions (no extra granularity regarding security, persistence, expiration management, etc ...). And a major drawback is the clients have to manually handle the selection of the correct database, which is error prone for clients targeting multiple databases at the same time.
Now, if you still want to use multiple databases, there is a way to make it work with redis-py and Lua scripting.
redis-py does not define a wrapper for the SELECT command (normally used to switch the current database), because of the underlying thread-safe connection pool implementation. But nothing prevents you to call SELECT from a Lua script.
Consider the following example:
$ redis-cli
SELECT 0
SET mykey db0
SELECT 1
SET mykey db1
The following script displays the value of mykey in the 2 databases from the same client connection.
import redis
pool = redis.ConnectionPool(host='localhost', port=6379, db=0)
r = redis.Redis(connection_pool=pool)
lua1 = """
redis.call("select", ARGV[1])
return redis.call("get",KEYS[1])
"""
script1 = r.register_script(lua1)
lua2 = """
redis.call("select", ARGV[1])
local ret = redis.call("get",KEYS[1])
redis.call("select", ARGV[2])
return ret
"""
script2 = r.register_script(lua2)
print r.get("mykey")
print script2( keys=["mykey"], args = [1,0] )
print r.get("mykey"), "ok"
print
print r.get("mykey")
print script1( keys=["mykey"], args = [1] )
print r.get("mykey"), "misleading !!!"
Script lua1 is naive: it just selects a given database before returning the value. Its usage is misleading, because after its execution, the current database associated to the connection has changed. Don't do this.
Script lua2 is much better. It takes the target database and the current database as parameters. It makes sure that the current database is reactivated before the end of the script, so that next command applied on the connection still run in the correct database.
Unfortunately, there is no command to guess the current database in the Lua script, so the client has to provide it systematically. Please note the Lua script must reset the current database at the end whatever happens (even in case of previous error), so it makes complex scripts cumbersome and awkward.
In the redis protocol specification, under the "Multi-bulk replies section":
A Multi bulk reply is used to return an array of other replies. Every element of a Multi Bulk Reply can be of any kind, including a nested Multi Bulk Reply.
However, I can't figure out a way to get Redis to return such output. Can anyone provide an example?
Only certain commands (especially those returning list of values) return multi-bulk replies, you can try by using LRANGE for example but you can check the command reference for more details.
Usually multi-bulk replies are only 1-level deep but some Redis commands can return nested multi-bulk replies (max 2 levels), notably EXEC (depending on the commands executed while inside the transaction context) and both EVAL / EVALSHA (depending on the value returned by the Lua script).
Here is an example using EXEC:
redis 127.0.0.1:6379> MULTI
OK
redis 127.0.0.1:6379> LPUSH metavars foo foobar hoge
QUEUED
redis 127.0.0.1:6379> LRANGE metavars 0 -1
QUEUED
redis 127.0.0.1:6379> EXEC
1) (integer) 4
2) 1) "hoge"
2) "foobar"
3) "foo"
4) "metavars"
The second element of the multi-bulk reply to EXEC is a multi-bulk itsef.
PS: I added a clarification in the comments regarding the actual maximum level of nesting of multi-bulk replies when using Lua scripts. tl;dr: there's basically no limit.
I want to delete all keys. I want everything wiped out and give me a blank database.
Is there a way to do this in Redis client?
With redis-cli:
FLUSHDB – Deletes all keys from the connection's current database.
FLUSHALL – Deletes all keys from all databases.
For example, in your shell:
redis-cli flushall
Heads up that FLUSHALL may be overkill. FLUSHDB is the one to flush a database only. FLUSHALL will wipe out the entire server. As in every database on the server. Since the question was about flushing a database I think this is an important enough distinction to merit a separate answer.
Answers so far are absolutely correct; they delete all keys.
However, if you also want to delete all Lua scripts from the Redis instance, you should follow it by:
SCRIPT FLUSH
The OP asks two questions; this completes the second question (everything wiped).
FLUSHALL
Remove all keys from all databases
FLUSHDB
Remove all keys from the current database
SCRIPT FLUSH
Remove all the scripts from the script cache.
If you're using the redis-rb gem then you can simply call:
your_redis_client.flushdb
you can use flushall in your terminal
redis-cli> flushall
This method worked for me - delete everything of current connected Database on your Jedis cluster.
public static void resetRedis() {
jedisCluster = RedisManager.getJedis(); // your JedisCluster instance
for (JedisPool pool : jedisCluster.getClusterNodes().values()) {
try (Jedis jedis = pool.getResource()) {
jedis.flushAll();
}
catch (Exception ex){
System.out.println(ex.getMessage());
}
}
}
One more option from my side:
In our production and pre-production databases there are thousands of keys. Time to time we need to delete some keys (by some mask), modify by some criteria etc. Of course, there is no way to do it manually from CLI, especially having sharding (512 logical dbs in each physical).
For this purpose I write java client tool that does all this work. In case of keys deletion the utility can be very simple, only one class there:
public class DataCleaner {
public static void main(String args[]) {
String keyPattern = args[0];
String host = args[1];
int port = Integer.valueOf(args[2]);
int dbIndex = Integer.valueOf(args[3]);
Jedis jedis = new Jedis(host, port);
int deletedKeysNumber = 0;
if(dbIndex >= 0){
deletedKeysNumber += deleteDataFromDB(jedis, keyPattern, dbIndex);
} else {
int dbSize = Integer.valueOf(jedis.configGet("databases").get(1));
for(int i = 0; i < dbSize; i++){
deletedKeysNumber += deleteDataFromDB(jedis, keyPattern, i);
}
}
if(deletedKeysNumber == 0) {
System.out.println("There is no keys with key pattern: " + keyPattern + " was found in database with host: " + host);
}
}
private static int deleteDataFromDB(Jedis jedis, String keyPattern, int dbIndex) {
jedis.select(dbIndex);
Set<String> keys = jedis.keys(keyPattern);
for(String key : keys){
jedis.del(key);
System.out.println("The key: " + key + " has been deleted from database index: " + dbIndex);
}
return keys.size();
}
}
Writing such kind of tools I find very easy and spend no more then 5-10 min.
Use FLUSHALL ASYNC if using (Redis 4.0.0 or greater) else FLUSHALL.
https://redis.io/commands/flushall
Note: Everything before executing FLUSHALL ASYNC will be evicted. The changes made during executing FLUSHALL ASYNC will remain unaffected.
FLUSHALL Deletes all the Keys of All exisiting databases .
FOr Redis version > 4.0 , FLUSHALL ASYNC is supported which runs in a background thread wjthout blocking the server
https://redis.io/commands/flushall
FLUSHDB - Deletes all the keys in the selected Database .
https://redis.io/commands/flushdb
The time complexity to perform the operations will be O(N) where N being the number of keys in the database.
The Response from the redis will be a simple string "OK"
Open redis-cli and type:
FLUSHALL
You can use FLUSHALL which will delete all keys from your every database.
Where as FLUSHDB will delete all keys from our current database.
Stop Redis instance.
Delete RDB file.
Start Redis instance.
redis-cli -h <host> -p <port> flushall
It will remove all data from client connected(with host and port)
After you start the Redis-server using:service redis-server start --port 8000 or redis-server.
Use redis-cli -p 8000 to connect to the server as a client in a different terminal.
You can use either
FLUSHDB - Delete all the keys of the currently selected DB. This command never fails. The time-complexity for this operation is O(N), N being the number of keys in the database.
FLUSHALL - Delete all the keys of all the existing databases, not just the currently selected one. This command never fails. The time-complexity for this operation is O(N), N being the number of keys in all existing databases.
Check the documentation for ASYNC option for both.
If you are using Redis through its python interface, use these two functions for the same functionality:
def flushall(self):
"Delete all keys in all databases on the current host"
return self.execute_command('FLUSHALL')
and
def flushdb(self):
"Delete all keys in the current database"
return self.execute_command('FLUSHDB')
i think sometimes stop the redis-server and delete rdb，aof files。
make sure there’s no data can be reloading.
then start the redis-server,now it's new and empty.
You can use FLUSHDB
e.g
List databases:
127.0.0.1:6379> info keyspace
# Keyspace
List keys
127.0.0.1:6379> keys *
(empty list or set)
Add one value to a key
127.0.0.1:6379> lpush key1 1
(integer) 1
127.0.0.1:6379> keys *
1) "key1"
127.0.0.1:6379> info keyspace
# Keyspace
db0:keys=1,expires=0,avg_ttl=0
Create other key with two values
127.0.0.1:6379> lpush key2 1
(integer) 1
127.0.0.1:6379> lpush key2 2
(integer) 2
127.0.0.1:6379> keys *
1) "key1"
2) "key2"
127.0.0.1:6379> info keyspace
# Keyspace
db0:keys=2,expires=0,avg_ttl=0
List all values in key2
127.0.0.1:6379> lrange key2 0 -1
1) "2"
2) "1"
Do FLUSHDB
127.0.0.1:6379> flushdb
OK
List keys and databases
127.0.0.1:6379> keys *
(empty list or set)
127.0.0.1:6379> info keyspace
# Keyspace
Your questions seems to be about deleting entire keys in a database. In this case you should try:
Connect to redis. You can use the command redis-cli (if running on port 6379), else you will have to specify the port number also.
Select your database (command select {Index})
Execute the command flushdb
If you want to flush keys in all databases, then you should try flushall.
you can use following approach in python
def redis_clear_cache(self):
try:
redis_keys = self.redis_client.keys('*')
except Exception as e:
# print('redis_client.keys() raised exception => ' + str(e))
return 1
try:
if len(redis_keys) != 0:
self.redis_client.delete(*redis_keys)
except Exception as e:
# print('redis_client.delete() raised exception => ' + str(e))
return 1
# print("cleared cache")
return 0
This works for me: redis-cli KEYS \* | xargs --max-procs=16 -L 100 redis-cli DEL
It list all Keys in redis, then pass using xargs to redis-cli DEL, using max 100 Keys per command, but running 16 command at time, very fast and useful when there is not FLUSHDB or FLUSHALL due to security reasons, for example when using Redis from Bitnami in Docker or Kubernetes. Also, it doesn't require any additional programming language and it just one line.
If you want to clear redis in windows:
find redis-cli in
C:\Program Files\Redis
and run FLUSHALL command.
Its better if you can have RDM (Redis Desktop Manager).
You can connect to your redis server by creating a new connection in RDM.
Once its connected you can check the live data, also you can play around with any redis command.
Opening a cli in RDM.
1) Right click on the connection you will see a console option, just click on it a new console window will open at the bottom of RDM.
Coming back to your question FLUSHALL is the command, you can simply type FLUSHALL in the redis cli.
Moreover if you want to know about any redis command and its proper usage, go to link below.
https://redis.io/commands.
There are different approaches. If you want to do this from remote, issue flushall to that instance, through command line tool redis-cli or whatever tools i.e. telnet, a programming language SDK. Or just log in that server, kill the process, delete its dump.rdb file and appendonly.aof(backup them before deletion).
If you are using Java then from the documentation, you can use any one of them based on your use case.
/**
* Remove all keys from all databases.
*
* #return String simple-string-reply
*/
String flushall();
/**
* Remove all keys asynchronously from all databases.
*
* #return String simple-string-reply
*/
String flushallAsync();
/**
* Remove all keys from the current database.
*
* #return String simple-string-reply
*/
String flushdb();
/**
* Remove all keys asynchronously from the current database.
*
* #return String simple-string-reply
*/
String flushdbAsync();
Code:
RedisAdvancedClusterCommands syncCommands = // get sync() or async() commands
syncCommands.flushdb();
Read more: https://github.com/lettuce-io/lettuce-core/wiki/Redis-Cluster
For anyone wondering how to do this in C# it's the same as the answer provided for Python for this same question.
I am using StackExchange.Redis v2.2.88 for a dot net (core) 5 project. I only need to clear my keys for integration testing and I have no purpose to do this in production.
I checked what is available in intellisense and I don't see a stock way to do this with the existing API. I imagine this is intentional and by design. Luckily the API does expose an Execute method.
I tested this by doing the following:
Opened up a command window. I am using docker, so I did it through docker.
Type in redis-cli which starts the CLI
Type in KEYS * and it shows me all of my keys so I can verify they exist before and after executing the following code below:
//Don't abuse this, use with caution
var cache = ConnectionMultiplexer.Connect(
new ConfigurationOptions
{
EndPoints = { "localhost:6379" }
});
var db = _cache.GetDatabase();
db.Execute("flushdb");
Type in KEYS * again and view that it's empty.
Hope this helps anyone looking for it.