[jira] [Closed] (FLINK-17074) Deprecate DataStream.keyBy() that use tuple/expression keys

["Aljoscha Krettek (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-17074?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Aljoscha Krettek closed FLINK-17074.
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    Resolution: Done

master: 4f106c50194886cb6e98b993785481192485479c..db3c3418edee55f103bec3bf0ce9caffc947d2da

> 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.



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