[jira] [Closed] (FLINK-6465) support FIRST_VALUE on Table API & SQL

["Kurt Young (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-6465?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Kurt Young closed FLINK-6465.
-----------------------------
    Resolution: Unresolved

> support FIRST_VALUE on Table API & SQL
> --------------------------------------
>
>                 Key: FLINK-6465
>                 URL: https://issues.apache.org/jira/browse/FLINK-6465
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Table API & SQL
>            Reporter: Hequn Cheng
>            Assignee: sunjincheng
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> {{FIRST_VALUE}} is a OVER WINDOW function. In this JIRA. will add {{FIRST_VALUE}} function support on TableAPI & SQL.
> *Syntax:*
> FIRST_VALUE ( [scalar_expression ] )   
>     OVER ( [ partition_by_clause ] order_by_clause [ rows_range_clause ] )  [About OVER WINDOWS|https://ci.apache.org/projects/flink/flink-docs-release-1.4/dev/table/tableApi.html#over-windows]
> scalar_expression
> Is the value to be returned. scalar_expression can be a column, or other arbitrary expression that results in a single value. Other analytic functions are not permitted.
> *NOTE:*
> *  {{FIRST_VALUE}} if used for OVER WINDOW, e.g.: 
> {code}
> SELECT A, B, FIRST_VALUE(C) OVER (ORDER BY E) AS firstValue FROM tab
> {code}
> * OVER WINDOW's retraction is expensive(currently not supported yet), and this JIRA. does not implement Retract logic of {{FIRST_VALUE}}.



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