[jira] [Updated] (SPARK-30335) Clarify behavior of FIRST and LAST without OVER caluse.

["Dongjoon Hyun (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-30335?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Dongjoon Hyun updated SPARK-30335:
----------------------------------
    Component/s: Documentation

> Clarify behavior of FIRST and LAST without OVER caluse.
> -------------------------------------------------------
>
>                 Key: SPARK-30335
>                 URL: https://issues.apache.org/jira/browse/SPARK-30335
>             Project: Spark
>          Issue Type: New Feature
>          Components: Documentation, SQL
>    Affects Versions: 3.1.0
>            Reporter: xqods9o5ekm3
>            Assignee: Hyukjin Kwon
>            Priority: Major
>             Fix For: 3.1.0
>
>
> Unlike many databases, Spark SQL allows usage of {{FIRST}} and {{LAST}} in non-analytic contexts.
>  
> At the moment {{FIRST}}
>  
> > first(expr[, isIgnoreNull]) - Returns the first value of {{expr}} for a group of rows. If {{isIgnoreNull}} is true, returns only non-null values.
>  
> and {{LAST}}
>  
> > last(expr[, isIgnoreNull]) - Returns the last value of {{expr}} for a group of rows. If {{isIgnoreNull}} is true, returns only non-null values.
>  
> descriptions, suggest that their behavior is deterministic and many users assume that it return specific values for example when query 
>  
> {code:sql}
> SELECT first(foo)
> FROM (
>     SELECT * FROM table ORDER BY bar
> )
> {code}
> That however doesn't seem to be the case.
> To make situation worse, it seems to work (for example on small samples in local mode).



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