[SPARK-13235] Remove an Extra Distinct in Union

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.0
• Fix Version/s: 2.0.0
• Component/s: SQL
• Assignee: Xiao Li
• Reporter: Xiao Li
• Created: 08/Feb/16 20:57
• Updated: 11/Feb/16 07:50
• Resolved: 11/Feb/16 07:50

Description

Union Distinct has two Distinct that generate two Aggregation in the plan.

sql("select * from t0 union select * from t0").explain(true)

== 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

Issue Links

• blocks: SPARK-13236 SQL generation support for Set Operations
• links to: [Github] Pull Request #11120 (gatorsmile)