JoelWee commented on a change in pull request #9186: URL: https://github.com/apache/kafka/pull/9186#discussion_r485244413
########## File path: streams/src/main/java/org/apache/kafka/streams/kstream/internals/KStreamKTableJoinProcessor.java ########## @@ -58,22 +58,23 @@ public void init(final ProcessorContext context) { @Override public void process(final K1 key, final V1 value) { - // we do join iff keys are equal, thus, if key is null we cannot join and just ignore the record - // If {@code keyMapper} returns {@code null} it implies there is no match, + // We allow null keys unless {@code keyMapper} returns {@code null} and we ignore it as invalid. Review comment: Yep makes sense. Have updated it now. Just noting here that this means we're changing a [test](https://github.com/apache/kafka/pull/9186/files#diff-e3715715832b244da2d8787362b0c570R230) we previously had ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org