I’ve read many blog posts and comments about how awesome projections are at doing temporal queries that are otherwise extremely difficult to achieve in SQL.
I’ve also read that projections are beta and experimental, and that this is the reason that there is almost zero documentation and examples. I’ve read the blog posts and seen the overly simplistic “this projection counts messages of type x” and “if the CPU usage goes over 40%, emit another message” examples. These examples are too simple to be useful.
Despite projections being considered beta, is there at least beta documentation that could be released? Any examples of gathering data from multiple messages related by time?
Let’s say I wanted to emit an event that contained the average CPU usage for the past hour, every hour, how would I do that with a projection?
If I already had say, a week’s worth of CPU usage events in my event store, could a projection process those and aggregate that data into new hourly CPU average messages? Could one projection handle both of these cases, or would I need to write separate ones?
Thanks for the help.