Redis中keys()方法作用原理是什么？

Question

鄙人蠢，读不懂redis源码～
有一天用redis-py连上Redis备用服务器，想看一下某类型的key有多少个。

rds = redis.Redis(ip, host)
print len(rds.keys('xxx_*'))

最后有大概400w个，阻塞了很久才算出来结果。
令我疑惑的是，这个客户端进程CPU占用率一直在100%以上（为什么会超过100%我也不知道），反倒内存占用率不高。

理论上keys的运算结果应该是服务端计算出来的，客户端接收数据顶多就是内存消耗多点儿，为什么实际情况中客户端CPU占用率如此之高，客户端自己做了什么奇怪的计算？

Answer 1

Traversing matches is definitely slow. The author has said that try not to use the keys command

Answer 2

The reason for the high CPU is mainly decoding the transmission format and converting it into a python object

Answer 3

Are you using top to watch? More than 100% is probably because of the multi-core CPU

It is best not to use key. You can use redis-rdb-tools, a small tool of redis. Someone seems to have mentioned how to use it here