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https://issues.apache.org/jira/browse/FLINK-40483?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dian Fu reassigned FLINK-40483:
-------------------------------
Assignee: Timo Theusner
> Support batch Top-N optimization for ROW_NUMBER()
> -------------------------------------------------
>
> Key: FLINK-40483
> URL: https://issues.apache.org/jira/browse/FLINK-40483
> Project: Flink
> Issue Type: Improvement
> Components: Table SQL / Planner
> Reporter: Timo Theusner
> Assignee: Timo Theusner
> Priority: Major
>
> The batch planner does not optimize {{ROW_NUMBER() OVER (PARTITION BY … ORDER
> BY …) … WHERE rn <= N}} into a Top-N Rank operator. It falls back to a full
> {{OverAggregate}} that computes the row number for every row, followed by a
> Calc filter. The streaming planner does perform this optimization
> (Rank/Deduplicate).
> Example query:
> {code:SQL}
> SELECT a, b, c FROM (
> SELECT a, b, c, ROW_NUMBER() OVER (PARTITION BY b ORDER BY c DESC) AS rn
> FROM MyTable) t
> WHERE rn = 1
> {code}
> Batch plan:
> {code:SQL}
> Calc(where=[w0$o0 = 1])
> +- OverAggregate(ROW_NUMBER(*) … UNBOUNDED PRECEDING .. CURRENT ROW)
> +- Sort(b ASC, c DESC)
> +- Exchange(hash[b])
> {code}
> Streaming plan:
> {code:SQL}
> Rank(rankType=[ROW_NUMBER], rankRange=[1,1], partitionBy=[b], orderBy=[c
> DESC])
> {code}
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