[
https://issues.apache.org/jira/browse/FLINK-17074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17264243#comment-17264243
]
Theo Diefenthal commented on FLINK-17074:
-----------------------------------------
What would now be the preferred approach to select multiple fields from a POJO
as key? Say I have a POJO with 10 fields and I want to use three of them (with
different types) as key. With the old API, I just specified the three field
names. Now I need to build up a KeySelector, create a tuple and put my fields
in there and build up proper field types deduced from the POJO field types
myself? Is there a utility method somewhere?
> Deprecate DataStream.keyBy() that use tuple/expression keys
> -----------------------------------------------------------
>
> Key: FLINK-17074
> URL: https://issues.apache.org/jira/browse/FLINK-17074
> Project: Flink
> Issue Type: Improvement
> Components: API / DataStream, API / Scala
> Reporter: Aljoscha Krettek
> Assignee: Etienne Chauchot
> Priority: Major
> Labels: pull-request-available, starter
> Fix For: 1.11.0
>
>
> Currently you can either specify a {{KeySelector}}, tuple positions, and
> expression keys? I think {{KeySelectors}} are strictly superior and with
> lambdas (or function references) quite easy to use. Tuple/expression keys
> use reflection underneath to do the field accesses, so performance is
> strictly worse. Also, when using a {{KeySelector}} you will have a meaningful
> key type {{KEY}} in your operations while for tuple/expression keys the key
> type is simply {{Tuple}}.
> Tuple/expression keys were introduced before Java got support for lambdas in
> Java 8 and before we added the Table API. Nowadays, using a lambda is little
> more typing than using an expression key but is (possibly) faster and more
> type safe. The Table API should be used for these more
> expression-based/relational use cases.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
