[jira] [Commented] (FLINK-970) Implement a first(n) operator

["Stephan Ewen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-970?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14042039#comment-14042039 ] 

Stephan Ewen commented on FLINK-970:
------------------------------------

There is a draft for a "distinct" operator which would solve some cases (first 1, per group).

The general version of "first" or "first 2" would be "top k", which would be a very valueable addition. Especially "top k over <order>".

> Implement a first(n) operator
> -----------------------------
>
>                 Key: FLINK-970
>                 URL: https://issues.apache.org/jira/browse/FLINK-970
>             Project: Flink
>          Issue Type: New Feature
>            Reporter: Timo Walther
>            Assignee: Timo Walther
>            Priority: Minor
>
> It is only syntactic sugar, but I had many cases where I just needed the first element  or the first 2 elements in a GroupReduce.
> E.g. Instead of
> {code:java}
> .reduceGroup(new GroupReduceFunction<String, String>() {
> 					@Override
> 					public void reduce(Iterator<String> values, Collector<String> out) throws Exception {
> 						out.collect(values.next());
> 					}
> 				})
> {code}
> {code:java}
> .first()
> {code}



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