Dealing with sparse values in RavenDB timeseries

I got an interesting question while discussing timeseries, and I thought it would make for a good blog post. Consider the timeseries that we have on the right. It shows a particular sensor value over a period of time.

The sensor in question reports data only when the value changes, but we want to get the data on every 30 minutes scale. How can we do that? It turns out that this is pretty easy to do by just asking RavenDB to do so. No, there isn’t a specific feature for that, but we don’t need to.

All we have to do here is just write the logic as a query function. I’ll admit that date handling in JS isn’t nice, but it works. And it gives us the results in the right tempo for us to do something about it.

Here is how the final data looks like:

Not very exciting, I know, but RavenDB it the kind of database that aims to sit there do stuff, not get you all hot and bothered watching your production systems melt.