Redis command to get all available keys?

Question

Is there a Redis command for fetching all keys in the database? I have seen some python-redis libraries fetching them. But was wondering if it is possible from redis-client.

Answer 1

SCAN doesn't require the client to load all the keys into memory like KEYS does. SCAN gives you an iterator you can use. I had a 1B records in my redis and I could never get enough memory to return all the keys at once.

Here is a python snippet to get all keys from the store matching a pattern and delete them:

import redis
r = redis.StrictRedis(host='localhost', port=6379, db=0)
for key in r.scan_iter("key_pattern*"):
    print key

Answer 2

KEYS pattern

Available since 1.0.0.

Time complexity: O(N) with N being the number of keys in the database, under the assumption that the key names in the database and the given pattern have limited length.

Returns all keys matching pattern.

Warning : This command is not recommended to use because it may ruin performance when it is executed against large databases instead of KEYS you can use SCAN or SETS.

Example of KEYS command to use :

redis> MSET firstname Jack lastname Stuntman age 35
"OK"
redis> KEYS *name*
1) "lastname"
2) "firstname"
redis> KEYS a??
1) "age"
redis> KEYS *
1) "lastname"
2) "age"
3) "firstname"

Answer 3

Updated for Redis 2.8 and above

As noted in the comments of previous answers to this question, KEYS is a potentially dangerous command since your Redis server will be unavailable to do other operations while it serves it. Another risk with KEYS is that it can consume (dependent on the size of your keyspace) a lot of RAM to prepare the response buffer, thus possibly exhausting your server's memory.

Version 2.8 of Redis had introduced the SCAN family of commands that are much more polite and can be used for the same purpose.

The CLI also provides a nice way to work with it:

$ redis-cli --scan --pattern '*'