I think the cheat sheet might be wrong regarding :window/session-key. >This key can represent any totally ordered domain, e.g. :event-time but it's supposed to be the key the session belongs to, not the one defining the session size as :window/window-key.

BTW, is it possible to get a window per some key (e.g user-id) as in session, but with any windowing strategy? Alternatively, is it possible to have an infinite session, effectively getting a global window per user-id for example?

Wouldn't you set the group-by key on the task?

@camechis I searched the cheat sheet to reply and found :group-key which I wasn't aware of. I don't think :group-by-key affects windowing, but seems like :group-key does. Not sure though.

It's not in the user guide

I think it organizes the segments by that key

In the window

So when your trigger fires all the segments will be organized by the key

Yeah I just now saw it in onyx-examples

This is cool. I thought :group-by-key only routed segments to the same peer.

Nope it definitely changes how segments are organized in your window

We used to the same

Still, I'd like an actual window per group, triggering them separately etc, but probably not necessary for my case.

@yonatanel Re: session-key, yeah. I think that sentence should just be removed from the description. Can you PR to remove that from information_model.cljc?

Yes, set :onyx/group-by-key or :onyx/group-fn on the corresponding task that's windowed.

You can access the group in the trigger sync function's extent-state parameter under the :group key. I think its the 2nd to the last parameter passed to sync

:onyx/group-by-key does both hash routing, and discretization of windows by group. We were considering changing group-by-key to be renamed to hash-route, and having a separate parameter on the window named group-by which automatically does hash routing too, but we punted for now.

The backing windows in a grouped window are completely isolated from one another, and have independent triggers.

@michaeldrogalis This is a strong feature and I think the docs should show it off more. Thanks!