Hello everyone, I would like to start a discussion on KIP-1340 Pass Join Key to `ValueJoinerWithKey` in Streams-GlobalKTable Joins < https://cwiki.apache.org/confluence/display/KAFKA/KIP-1340%3A+Pass+Join+Key+to+%60ValueJoinerWithKey%60+in+Streams-GlobalKTable+Joins >
This proposal aims to introduce joinOnMappedKey and leftJoinOnMappedKey, new KStream methods that pass the mapped join key (the result of the user-supplied KeyValueMapper) into ValueJoinerWithKey for stream-globalTable joins. The existing join/leftJoin overloads pass the stream record's key into the joiner instead, contradicting KIP-149's contract that readOnlyKey is the join key and silently producing wrong values if a joiner intends to read the real join key. The existing overloads will be deprecated and removed in a future major release. Best regards, Lucy Liu
