Get all keys in Redis database with python

Yes, use keys() from the StrictRedis module:

>>> import redis
>>> r = redis.StrictRedis(host=YOUR_HOST, port=YOUR_PORT, db=YOUR_DB)
>>> r.keys()

Giving a null pattern will fetch all of them. As per the page linked:

keys(pattern='*')

Returns a list of keys matching pattern

import redis
r = redis.Redis("localhost", 6379)
for key in r.scan_iter():
       print key

using Pyredis library

scan command

Available since 2.8.0.

Time complexity: O(1) for every call. O(N) for a complete iteration, including enough command calls for the cursor to return back to 0. N is the number of elements inside the collection..

Use scan_iter()

scan_iter() is superior to keys() for large numbers of keys because it gives you an iterator you can use rather than trying to load all the keys into memory.

I had a 1B records in my redis and I could never get enough memory to return all the keys at once.

SCANNING KEYS ONE-BY-ONE

Here is a python snippet using scan_iter() to get all keys from the store matching a pattern and delete them one-by-one:

import redis
r = redis.StrictRedis(host='localhost', port=6379, db=0)
for key in r.scan_iter("user:*"):
    # delete the key
    r.delete(key)

SCANNING IN BATCHES

If you have a very large list of keys to scan - for example, larger than >100k keys - it will be more efficient to scan them in batches, like this:

import redis
from itertools import izip_longest

r = redis.StrictRedis(host='localhost', port=6379, db=0)

# iterate a list in batches of size n
def batcher(iterable, n):
    args = [iter(iterable)] * n
    return izip_longest(*args)

# in batches of 500 delete keys matching user:*
for keybatch in batcher(r.scan_iter('user:*'),500):
    r.delete(*keybatch)

I benchmarked this script and found that using a batch size of 500 was 5 times faster than scanning keys one-by-one. I tested different batch sizes (3,50,500,1000,5000) and found that a batch size of 500 seems to be optimal.

Note that whether you use the scan_iter() or keys() method, the operation is not atomic and could fail part way through.

DEFINITELY AVOID USING XARGS ON THE COMMAND-LINE

I do not recommend this example I found repeated elsewhere. It will fail for unicode keys and is incredibly slow for even moderate numbers of keys:

redis-cli --raw keys "user:*"| xargs redis-cli del

In this example xargs creates a new redis-cli process for every key! that's bad.

I benchmarked this approach to be 4 times slower than the first python example where it deleted every key one-by-one and 20 times slower than deleting in batches of 500.