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