Thanks for reacting ;)
I did some simulations, and after them, I want of course to parallelize this process of processing 2 billions facts. But as far as I wrote, Drools engine, can't do this. And I have to create threads manually in application (with pool of sessions). Am I right? Tuning number of data sounds fine to me, so I will try method with "rule latch" too (but I have to read about this, because, I don't know what is it, and I don't want to waste your time ;) But still I don't know how to use StatefulSessions to do this...
Summarising, there are 3 methods to do, what I want to do (apart of a scalability problem - yet ;)
1.)with StatelessSession for one fact at time and "activation group"
2.)"rule latch" - I have to read more about it
3.)with a pool of StatefulSessions that I reuse - but I still don't know how to do it using StatefulSessions
Really thanks for help ;)
P.S. I use Drools 5 :)