esper how to find ID that exists in streamA but NOT EXITS in streamB

Question

The problem is pretty simple: extract only the not exists records from 2 different streams using Esper engine.
ID exists in streamA but NOT EXITS in streamB.

In SQL it would look like this:

SELECT *
FROM   tableA
WHERE  NOT EXISTS (SELECT *
                   FROM   tableB
                   WHERE  tableA.Id = tableB.Id)

I've tried it Esper style but it doesn't work:

SELECT *
FROM  streamA.win:ext_timed(timestamp, 5 seconds) as stream_A
WHERE NOT EXSITS
    (SELECT stream_B.Id
     FROM streamB.win:ext_timed(timestamp, 5 seconds) as stream_B
     WHERE stream_A.Id = stream_B.Id)

Sadly if stream_A.Id inserted before stream_B.id than it will answer the query conditions and the query won't work.

Any suggestions on how to identify "ID exists in streamA but NOT EXITS in streamB" using Esper?

Answer 1

One simple way is to time-order the stream, so that A and B are timestamp ordered before sending events in.

Or you could delay A such as this query:

select * from pattern [every a=streamA -> timer:interval(1 sec)] as delayed_a where not exists (... where delayed_a.a.id = b.id)

There is no need for an externally timed window for streamA. For externally timed behavior in general use external timer events.