如何从带分数列表的redis zset获取数据？

Question

I want to get data from zset with a score list, eg

zadd zset 1 a 2 b 3 c 4 d

I want a command like

'zrange zset [2, 4]'

and the result is

b, d

Thanks!

Answer 1

仅此一个ZRANGEBYSCORE命令。

Answer 2

you can use a piece of code to do this, like :

for score in score_list
    members = zrangebyscore(zset, score, score)
    member_list += members 

the time cost of ZRANGEBYSCORE is O(LOG(N)+M) and M is the count of members returned. so we can say the cost in our zrangebyscore is O(LOG(N)), N is the size of zset. So the overall time cost is O(M*LOG(N)) which M is the length of score_list. It will be the best time cost.

The only bad thing is we cost M RTTs in network transport. We can use the pipeline to speedup the queries.

redis document says:

A Request/Response server can be implemented so that it is able to process new requests even if the client didn't already read the old responses. This way it is possible to send multiple commands to the server without waiting for the replies at all, and finally read the replies in a single step.

So if you use pipeline tech, It will only cost one RTT time. And I think every language's client for redis has implemented the pipeline. good luck !