The concept groupwin is like the unaligned windows

问题:

groupwin

I use the meaning in esper:

This view groups events into sub-views by the value returned by the specified expression or the combination of values returned by a list of expressions.

I think it is that you have the ability to operate by group,not stream(the group by is used to control how aggregations are grouped.)

unaligned window

In google's dataflow ,unaligned windows means:

By unaligned windows, we mean windows which do not span the entirety of a data source, but instead only a subset of it, such as per-user windows.

And does these mean the same thing? Set<event> XXXX = eventStream.GroupByKey(XXX);

回答1:

Grouped windows: there is no relationship to aggregations and aggregations are operating only by the group-by clause if there is one. Grouped window for Esper is a way to define the subsets of events that are considered. That is useful various use cases, for example match-recognize pattern matching over a subset of events or just running some function over some subset of events or comparing previous events in the same group with "prev".

In general ability to "operate per-group" in Esper is done by contexts ie. context partition per key.