[jira] [Commented] (FLINK-3279) Optionally disable DistinctOperator combiner

["Fabian Hueske (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-3279?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15114942#comment-15114942 ] 

Fabian Hueske commented on FLINK-3279:
--------------------------------------

With a hash-based reduce combiner (FLINK-2237, PR #1517) and porting distinct from groupReduce to reduce, the cost of combining should go down.
But providing the option to disable it completely sounds like a good idea.

> Optionally disable DistinctOperator combiner
> --------------------------------------------
>
>                 Key: FLINK-3279
>                 URL: https://issues.apache.org/jira/browse/FLINK-3279
>             Project: Flink
>          Issue Type: New Feature
>          Components: DataSet API
>    Affects Versions: 1.0.0
>            Reporter: Greg Hogan
>            Priority: Minor
>
> Calling {{DataSet.distinct()}} executes {{DistinctOperator.DistinctFunction}} which is a combinable {{RichGroupReduceFunction}}. Sometimes we know that there will be few duplicate records and disabling the combine would improve performance.
> I propose adding {{public DistinctOperator<T> setCombinable(boolean combinable)}} to {{DistinctOperator}}.



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