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https://issues.apache.org/jira/browse/FLINK-21203?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17276366#comment-17276366
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wangpeibin commented on FLINK-21203:
------------------------------------
If the config option is needed. It may be like :
||Key||Default||Type||Description||
|table.optimizer.last-row.ignore-equal-rows|false|Boolean|Enables the strategy
for ignore equal rows with LastRow function in optimizer. Default is disabled. |
> Don’t collect -U&+U Row When they are equals In the LastRowFunction
> ---------------------------------------------------------------------
>
> Key: FLINK-21203
> URL: https://issues.apache.org/jira/browse/FLINK-21203
> Project: Flink
> Issue Type: Improvement
> Components: Table SQL / Runtime
> Reporter: wangpeibin
> Assignee: wangpeibin
> Priority: Major
>
> In the LastRowFunction , the -U&+U Row will be collected even if they are
> the same, which will increase calculation pressure of the next Operator.
>
> To avoid this, we can optimize the logic of DeduplicateFunctionHelper. Also,
> a config to enable the optimization will be added.
> With the sql followed:
> {quote}select * from
> (select
> *,
> row_number() over (partition by k order by proctime() desc ) as row_num
> from a
> ) t
> where row_num = 1
> {quote}
> Then input 2 row such as :
> {quote}Event("B","1","b"),
> Event("B","1","b")
> {quote}
> Now the output is:
> {quote}(true,+I[B, 1, b, 1])
> (false,-U[B, 1, b, 1])
> (true,+U[B, 1, b, 1])
> {quote}
> After the optimization, the output will be:
> {quote}(true,+I[B, 1, b, 1])
> {quote}
>
>
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