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https://issues.apache.org/jira/browse/SPARK-13235?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Herman van Hovell resolved SPARK-13235.
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Resolution: Fixed
Assignee: Xiao Li
Fix Version/s: 2.0.0
> Remove an Extra Distinct in Union
> ---------------------------------
>
> Key: SPARK-13235
> URL: https://issues.apache.org/jira/browse/SPARK-13235
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.0.0
> Reporter: Xiao Li
> Assignee: Xiao Li
> Fix For: 2.0.0
>
>
> Union Distinct has two Distinct that generate two Aggregation in the plan.
> {code}
> sql("select * from t0 union select * from t0").explain(true)
> {code}
> {code}
> == Parsed Logical Plan ==
> 'Project [unresolvedalias(*,None)]
> +- 'Subquery u_2
> +- 'Distinct
> +- 'Project [unresolvedalias(*,None)]
> +- 'Subquery u_1
> +- 'Distinct
> +- 'Union
> :- 'Project [unresolvedalias(*,None)]
> : +- 'UnresolvedRelation `t0`, None
> +- 'Project [unresolvedalias(*,None)]
> +- 'UnresolvedRelation `t0`, None
> == Analyzed Logical Plan ==
> id: bigint
> Project [id#16L]
> +- Subquery u_2
> +- Distinct
> +- Project [id#16L]
> +- Subquery u_1
> +- Distinct
> +- Union
> :- Project [id#16L]
> : +- Subquery t0
> : +- Relation[id#16L] ParquetRelation
> +- Project [id#16L]
> +- Subquery t0
> +- Relation[id#16L] ParquetRelation
> == Optimized Logical Plan ==
> Aggregate [id#16L], [id#16L]
> +- Aggregate [id#16L], [id#16L]
> +- Union
> :- Project [id#16L]
> : +- Relation[id#16L] ParquetRelation
> +- Project [id#16L]
> +- Relation[id#16L] ParquetRelation
> {code}
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