问Python和Redis。为什么scan_iter()比带mget()的key()慢得多？

EN

from datetime import datetime
from time import sleep
import redis
r = redis.StrictRedis(host='192.168.3.16', port=6379, decode_responses=True, db= 0)

def query_keys():
    start = datetime.now()
    redis_keys = r.keys(pattern='*')
    redis_keys = [x for x in redis_keys if not x.startswith('1_')]
    values = r.mget(redis_keys)
    end = datetime.now()
    print(str(len(values)) + ' values queried in ' + str(end - start) + ' with keys and mget.')
    
def query_scaniter():
    start = datetime.now()
    values = []
    for s in r.scan_iter():
        if not s.startswith('1_'):
            values.append(r.get(s))
    end = datetime.now()
    print(str(len(values)) + ' values queried in ' + str(end - start) + ' with scan_iter.')
    
def query_scaniter_mget():
    start = datetime.now()
    redis_keys = []
    for s in r.scan_iter():
        if not s.startswith('1_'):
            redis_keys.append(s)
    values = r.mget(redis_keys)
    end = datetime.now()
    print(str(len(values)) + ' values queried in ' + str(end - start) + ' with scan_iter and mget.')

for i in range(3):
    query_keys()
    query_scaniter()
    query_scaniter_mget()
    print('\n')
    sleep(5)

Output:
3532 values queried in 0:00:00.046872 with keys and mget.
3532 values queried in 0:00:00.781314 with scan_iter.
3532 values queried in 0:00:00.109385 with scan_iter and mget.


3526 values queried in 0:00:00.031245 with keys and mget.
3522 values queried in 0:00:00.812616 with scan_iter.
3522 values queried in 0:00:00.125007 with scan_iter and mget.


3529 values queried in 0:00:00.031246 with keys and mget.
3531 values queried in 0:00:00.797011 with scan_iter.
3530 values queried in 0:00:00.109357 with scan_iter and mget.