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https://issues.apache.org/jira/browse/FLINK-11944?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kurt Young closed FLINK-11944.
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Resolution: Duplicate
Fix Version/s: 1.9.0
> Support FirstRow and LastRow for SQL
> ------------------------------------
>
> Key: FLINK-11944
> URL: https://issues.apache.org/jira/browse/FLINK-11944
> Project: Flink
> Issue Type: New Feature
> Components: Table SQL / Runtime
> Reporter: Jark Wu
> Priority: Major
> Fix For: 1.9.0
>
>
> Usually there are some duplicate data in the source due to some reasons. In
> order to get a correct result, we need to do deduplication. FirstRow and
> LastRow are two different strategy for deduplication. The syntax of FirstRow
> and LastRow is similar to TopN, but order by a time attribute. For example:
> SELECT *
> FROM (
> SELECT *,
> ROW_NUMBER() OVER (PARTITION BY id ORDER BY proctime DESC) as rownum
> FROM T
> )
> WHERE rownum = 1
> Some information about FirstRow & LastRow.
> 1. the partition by key is the deduplicate key
> 2. can only order by a time attribute (either proctime or rowtime)
> 3. the rownum filter must be {{= 1}} or {{<= 1}}
> 4. it is FirstRow when order direction is ASC, LastRow when order direction
> is DESC
> This issue is aiming to optimize this query to a FirstLastRow node instead of
> Over plus Calc. And translate the it into physical operators.
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