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From "Apache Spark (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (SPARK-16208) Add `CollapseEmptyPlan` optimizer
Date Sat, 25 Jun 2016 09:28:55 GMT

     [ https://issues.apache.org/jira/browse/SPARK-16208?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Apache Spark reassigned SPARK-16208:
------------------------------------

    Assignee: Apache Spark

> Add `CollapseEmptyPlan` optimizer
> ---------------------------------
>
>                 Key: SPARK-16208
>                 URL: https://issues.apache.org/jira/browse/SPARK-16208
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Dongjoon Hyun
>            Assignee: Apache Spark
>            Priority: Minor
>
> This issue adds a new logical optimizer, `CollapseEmptyPlan`, to collapse a logical plain
consisting of only empty LocalRelations.
> **Before**
> {code}
> scala> sql("select a from (select explode(array(1,2,3)) a) where 1=0 group by a having
count(*)>1 order by a").explain
> == Physical Plan ==
> *Sort [a#15 ASC], true, 0
> +- Exchange rangepartitioning(a#15 ASC, 200)
>    +- *Project [a#15]
>       +- *Filter (count(1)#17L > 1)
>          +- *HashAggregate(keys=[a#15], functions=[count(1)])
>             +- Exchange hashpartitioning(a#15, 200)
>                +- *HashAggregate(keys=[a#15], functions=[partial_count(1)])
>                   +- Generate explode([1,2,3]), false, false, [a#15]
>                      +- LocalTableScan <empty>
> {code}
> **After**
> {code}
> scala> sql("select a from (select explode(array(1,2,3)) a) where 1=0 group by a having
count(*)>1 order by a").explain
> == Physical Plan ==
> LocalTableScan <empty>, [a#15]
> {code}



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