[ https://issues.apache.org/jira/browse/KAFKA-3705?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16217718#comment-16217718 ]
Matthias J. Sax commented on KAFKA-3705: ---------------------------------------- It does not -- it's hard to do correctly. You can see that there a prototype PRs from [~jfilipiak] -- maybe he can comment on the current status? > Support non-key joining in KTable > --------------------------------- > > Key: KAFKA-3705 > URL: https://issues.apache.org/jira/browse/KAFKA-3705 > Project: Kafka > Issue Type: Bug > Components: streams > Reporter: Guozhang Wang > Labels: api > > Today in Kafka Streams DSL, KTable joins are only based on keys. If users > want to join a KTable A by key {{a}} with another KTable B by key {{b}} but > with a "foreign key" {{a}}, and assuming they are read from two topics which > are partitioned on {{a}} and {{b}} respectively, they need to do the > following pattern: > {code} > tableB' = tableB.groupBy(/* select on field "a" */).agg(...); // now tableB' > is partitioned on "a" > tableA.join(tableB', joiner); > {code} > Even if these two tables are read from two topics which are already > partitioned on {{a}}, users still need to do the pre-aggregation in order to > make the two joining streams to be on the same key. This is a draw-back from > programability and we should fix it. -- This message was sent by Atlassian JIRA (v6.4.14#64029)