storing time series in redis

Question

I need to store some timeseries data into redis. I have unix timestamps and that that i need to associate a value (timestamp <-> value)

I tried sorted sets having the timestamp as score (so i can do zrange on the timestamps) and the value as member.

127.0.0.1:6379> ZADD timeserie 1392141527245 10 1392141527275 12 1392141527100 10
(integer) 2
127.0.0.1:6379> zscan timeserie 0
1) "0"
2) 1) "10"
   2) "1392141527245"
   3) "12"
   4) "1392141527275"
127.0.0.1:6379>

But i hit a problem, members are nonrepeating while my values can be the same for different timestamps. Any idea how to approach this? Is another data type better?

Answer 1

An easy trick to solve this problem is to concatenate the timestamp and the value.

Instead of storing:

ZADD timeserie 1392141527245 10

you can store:

ZADD timeserie 1392141527245 10:1392141527245

Up to the application to encode/parse the value:timestamp format.

Sorted sets are implemented as a skip list plus a hash table, so they are not especially compact in memory. If the volume of your data is significant, you will be better served by another solution.

Some people use normal strings to encode time series, which are way more compact than sorted sets. You can find an example here: https://github.com/antirez/redis-timeseries

Answer 2

It's a sorted set, so indeed value can't repeat. Redis might not be the best tool for your usage, give a try to a specialised database like influxdb.