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https://issues.apache.org/jira/browse/SPARK-2176?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14035887#comment-14035887
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Yin Huai commented on SPARK-2176:
---------------------------------
Seems it is a bug related to Explain command.
When I use ...
{code}
hql("select * from src group by key")
{code}
The plan is ...
{code}
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
{code}
> extra unnecessary exchange operator in group by
> -----------------------------------------------
>
> Key: SPARK-2176
> URL: https://issues.apache.org/jira/browse/SPARK-2176
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Reporter: Reynold Xin
> Assignee: Yin Huai
>
> {code}
> 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]
> {code}
> There are two exchange operators.
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