WhereNotExists

Keeps each left event only for the times when no right event with the same key is alive.

An anti-semi-join: the output is the left payload, alive for the parts of its lifetime not covered by any right event with an equal key. Trill has no WhereExists counterpart. A Join that projects the left payload comes close, but it emits one copy of the left event for each overlapping right event with the same key, where a semi-join would emit one.

In the diagram, a:1 [1,5) survives as [1,2) and [4,5) around a:10 [2,4); b:2 [3,9) survives as [3,4) and [7,9) around b:20 [4,7); a:3 [6,8) survives whole.

As with LeftOuterJoin, slices whose end Trill cannot know when they start are emitted as start and end edges.

See also: Join, LeftOuterJoin, ClipEventDuration