Same happens for regular join, keys that appear only in one stream will make it to output KTable tC with a null for either input stream. I guess it's related to Kafka-3911 Enforce ktable Materialization or umbrella JIRA 3909, Queryable state for Kafka Streams?
On Mon, Jul 4, 2016 at 8:45 PM, Philippe Derome <phder...@gmail.com> wrote: > If we have two streams A and B for which we associate tables tA and tB, > then create a table tC as ta.leftJoin(tB, <some value joiner>) and then we > have a key kB in stream B but never made it to tA nor tC, do we need to > inject a pair (k,v) of (kB, null) into resulting change log for tC ? > > It sounds like it is definitely necessary if key kB is present in table tC > but if not, why add it? > > I have an example that reproduces this and would like to know if it is > considered normal, sub-optimal, or a defect. I don't view it as normal for > time being, particularly considering stream A as having very few keys and B > as having many, which could lead to an unnecessary large change log for C. > > Phil >
