[jira] [Comment Edited] (FLINK-9422) Dedicated operator for UNION on streaming tables with time attributes

["Hequn Cheng (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-9422?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16488298#comment-16488298 ] 

Hequn Cheng edited comment on FLINK-9422 at 5/24/18 1:54 AM:
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Hi, I agree that we need a dedicated operator. But I think adding a dedicated  {{DISTINCT}} operator is better, and the  {{DISTINCT}} operator would solve both the union problem and the distinct problem. The dedicated {{DISTINCT}} operator will only output append stream.


was (Author: hequn8128):
Hi, I agree that we need a dedicated operator. But I think adding a dedicated  {{DISTINCT}} operator is better, and the  {{DISTINCT}} operator would solve both the union problem and the distinct problem.

> Dedicated operator for UNION on streaming tables with time attributes
> ---------------------------------------------------------------------
>
>                 Key: FLINK-9422
>                 URL: https://issues.apache.org/jira/browse/FLINK-9422
>             Project: Flink
>          Issue Type: Improvement
>          Components: Table API & SQL
>            Reporter: Fabian Hueske
>            Assignee: Ruidong Li
>            Priority: Minor
>
> We can implement a dedicated operator for a {{UNION}} operator on tables with time attributes. Currently, {{UNION}} is translated into a {{UNION ALL}} and a subsequent {{GROUP BY}} on all attributes without aggregation functions. The state of the grouping operator is only clean up using state retention timers. 
> The dedicated operator would leverage the monotonicity property of the time attribute and watermarks to automatically clean up its state.



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