Hi I'm currently evaluating Cassandra as a potiantial database for storing time series data from lots of devices (IoT type of scenario). Currently we have a few thousand devices with X channels (measurements) that they report at different intervals (from 5 minutes and up).
I've created as simple test table to store the data: CREATE TABLE DataRaw( channelId int, sampleTime timestamp, value double, PRIMARY KEY (channelId, sampleTime) ) WITH CLUSTERING ORDER BY (sampleTime ASC); This schema seems to work ok, but I have queries that I need to support that I cannot easily figure out how to perform (except getting all the data out and iterate it myself). Query 1: For max and min queries, I not only want the maximum/minimum value, but also the corresponding timestamp. sampleTime value 2015-08-28 00:00 10 2015-08-28 01:00 15 2015-08-28 02:00 13 I'd like the max query to return both 2015-08-28 01:00 and 15. SELECT sampleTime, max(value) FROM DataRAW return the max value, but the first sampleTime. Also I wonder if Cassandra has built-in support for interpolation/extrapolation. Some sort of group by hour/day/week/month and even year function. Query 2: Give me hourly averages for channel X for yesterday. I'd expect to get 24 values each of which is the hourly average. Or give my daily averages for last year for a given channel. Should return 365 daily averages. Best regards Pål Andreassen 54°23'58"S 3°18'53"E Konsulent Mobil +47 982 85 504 pal.andreas...@bouvet.no<mailto:pal.andreas...@bouvet.no> Bouvet Norge AS Avdeling Grenland Uniongata 18, Klosterøya N-3732 Skien Tlf +47 23 40 60 00 bouvet.no<http://www.bouvet.no/?utm_campaign=e-post&utm_source=ansatt&utm_medium=email>
