Distinct

Removes duplicates among the events alive at each moment.

Distinct works on snapshots. At every moment, the output holds one event for each distinct value among the events alive then. With a selector, such as e => e.Key, two events are duplicates when the selector gives the same result for both, and the output payload is that result. Without a selector, Distinct compares whole payloads.

In the diagram, two a events overlap from 3 to 6, but the output has only one a at any moment. That a is split at 3 and at 6, where the number of a events alive changes. Distinct is built from GroupApply and Count, and each change in a group’s count starts a new output event. The output arrives as start and end edges.

See also: Where, GroupApply, Count (tumbling window)