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From "Timo Walther (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (FLINK-5722) Implement DISTINCT as dedicated operator
Date Wed, 08 Mar 2017 13:16:38 GMT

     [ https://issues.apache.org/jira/browse/FLINK-5722?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Timo Walther resolved FLINK-5722.
---------------------------------
       Resolution: Fixed
    Fix Version/s: 1.3.0

Fixed in 1.3.0: 7a629fc59ff206ba51f22e1bf35fe50882e63538

> Implement DISTINCT as dedicated operator
> ----------------------------------------
>
>                 Key: FLINK-5722
>                 URL: https://issues.apache.org/jira/browse/FLINK-5722
>             Project: Flink
>          Issue Type: Improvement
>          Components: Table API & SQL
>    Affects Versions: 1.2.0, 1.3.0
>            Reporter: Fabian Hueske
>            Assignee: Fabian Hueske
>             Fix For: 1.3.0
>
>
> DISTINCT is currently implemented for batch Table API / SQL as an aggregate which groups
on all fields. Grouped aggregates are implemented as GroupReduce with sort-based combiner.
> This operator can be more efficiently implemented by using ReduceFunction and hinting
a HashCombine strategy. The same ReduceFunction can be used for all DISTINCT operations and
can be assigned with appropriate forward field annotations.
> We would need a custom conversion rule which translates distinct aggregations (grouping
on all fields and returning all fields) into a custom DataSetRelNode.



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