[SPARK-2176] Extra unnecessary exchange operator in the result of an explain command

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.0.1, 1.1.0
• Component/s: SQL
• Target Version/s: 1.0.1, 1.1.0
• Assignee: Yin Huai
• Reporter: Reynold Xin
• Created: 18/Jun/14 07:30
• Updated: 18/Jun/14 18:28
• Resolved: 18/Jun/14 18:28

Description

hql("explain select * from src group by key").collect().foreach(println)

[ExplainCommand [plan#27:0]]
[ Aggregate false, [key#25], [key#25,value#26]]
[  Exchange (HashPartitioning [key#25:0], 200)]
[   Exchange (HashPartitioning [key#25:0], 200)]
[    Aggregate true, [key#25], [key#25]]
[     HiveTableScan [key#25,value#26], (MetastoreRelation default, src, None), None]

There are two exchange operators.

However, if we do not use explain...

hql("select * from src group by key")

res4: org.apache.spark.sql.SchemaRDD = 
SchemaRDD[8] at RDD at SchemaRDD.scala:100
== Query Plan ==
Aggregate false, [key#8], [key#8,value#9]
 Exchange (HashPartitioning [key#8:0], 200)
  Aggregate true, [key#8], [key#8]
   HiveTableScan [key#8,value#9], (MetastoreRelation default, src, None), None

The plan is fine.

Issue Links

• links to: Pull request