Current state: Under Discussion

Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]

JIRA: here [Change the link from KAFKA-1 to your own ticket]

Motivation

Kafka Streams enforces a strict non-null-key policy in the DSL across all key-dependent operations (like aggregations and joins). For left-joins, it might make sense to still accept a `null`, and add the left-hand record with an empty right-hand-side to the result.

Public Interfaces

This KIP won't change any public interfaces. However, It will change the behavior of several stream dsl operators:

• KStream left & outer join
• table KTable LeftJoin: foreign key may be null

Proposed Changes

Describe the new thing you want to do in appropriate detail. This may be fairly extensive and have large subsections of its own. Or it may be a few sentences. Use judgement based on the scope of the change.

Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users?
• If we are changing behavior how will we phase out the older behavior?
• If we need special migration tools, describe them here.
• When will we remove the existing behavior?

Test Plan

Describe in few sentences how the KIP will be tested. We are mostly interested in system tests (since unit-tests are specific to implementation details). How will we know that the implementation works as expected? How will we know nothing broke?

Rejected Alternatives

If there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.