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https://issues.apache.org/jira/browse/FLINK-17074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17090492#comment-17090492
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Etienne Chauchot commented on FLINK-17074:
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[~aljoscha] got it, only Datastream API, but what about other uses of keys in
the Datastream API, we should deprecate them as well no ?
{code:java}
public <K> DataStream<T> partitionCustom(Partitioner<K> partitioner, int field)
public <K> DataStream<T> partitionCustom(Partitioner<K> partitioner, String
field)
{code}
> 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
> Reporter: Aljoscha Krettek
> Assignee: Etienne Chauchot
> Priority: Major
> Labels: 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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