[jira] [Updated] (SPARK-32934) Improve the performance for NTH_VALUE,FIRST_VALUE,LAST_VALUE

["jiaan.geng (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-32934?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

jiaan.geng updated SPARK-32934:
-------------------------------
    Summary: Improve the performance for NTH_VALUE,FIRST_VALUE,LAST_VALUE  (was: Support a new window frame could improve the performance for NTH_VALUE,FIRST_VALUE,LAST_VALUE)

> Improve the performance for NTH_VALUE,FIRST_VALUE,LAST_VALUE
> ------------------------------------------------------------
>
>                 Key: SPARK-32934
>                 URL: https://issues.apache.org/jira/browse/SPARK-32934
>             Project: Spark
>          Issue Type: Sub-task
>          Components: SQL
>    Affects Versions: 3.1.0
>            Reporter: jiaan.geng
>            Priority: Major
>
> Spark SQL support some window function like  NTH_VALUE,FIRST_VALUE and LAST_VALUE
> If we specify window frame like
> {code:java}
> UNBOUNDED PRECEDING AND CURRENT ROW
> {code}
> or
> {code:java}
> UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
> {code}
> We can elimate some calculations.
> For example: if we execute the SQL show below:
> {code:java}
> SELECT NTH_VALUE(col,
>          2) OVER(ORDER BY rank UNBOUNDED PRECEDING
>         AND CURRENT ROW)
> FROM tab;
> {code}
> The output for row number greater than 1, return the fixed value. otherwise, return null. So we just calculate the value once and notice whether the row number less than 2.
> UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING is simpler.



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