kafka-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Jan Filipiak (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (KAFKA-3705) Support non-key joining in KTable
Date Tue, 17 Jan 2017 16:22:26 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-3705?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15826332#comment-15826332
] 

Jan Filipiak commented on KAFKA-3705:
-------------------------------------

Hi, with regard of what I am trying here, the GlobalKTable is not usefull.
 It could be usefull if its source would also emmit change events. (I would still have todo
the range lookup but i could save a repartition of my "bigger" table) The current design is
not usuable here. :'(   

> 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
(v6.3.4#6332)

Mime
View raw message