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https://issues.apache.org/jira/browse/SPARK-39169?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-39169:
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Assignee: (was: Apache Spark)
> Optimize FIRST when used as a single aggregate function
> -------------------------------------------------------
>
> Key: SPARK-39169
> URL: https://issues.apache.org/jira/browse/SPARK-39169
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.3.0
> Reporter: Vitalii Li
> Priority: Major
>
> When `FIRST` is a single aggregate function in `Aggregate` we could either
> rewrite whole query or optimize execution logic.
> * Plan => `SELECT FIRST(<col>) FROM <table>` => `SELECT <col> FROM <table>
> LIMIT 1`. Note that setting `ignoreNulls` to `true` should block such rewrite
> since returns could differ in case all values of <col> are `NULL`
> * Execution => `SELECT FIRST(<col>) FROM <table> GROUP BY <some_col>` =>
> short circuit iteration per key once a value for `FIRST` is set.
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