Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/2262#discussion_r17096919
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/basicOperators.scala ---
@@ -97,6 +97,7 @@ case class Limit(limit: Int, child: SparkPlan)
// partition local limit -> exchange into one partition -> partition
local limit again
override def output = child.output
+ override def outputPartitioning = SinglePartition
--- End diff --
This is not changing the implementation, just correcting a bug that
prevents exchange operators from being inserted when we need them.
On Sep 3, 2014 11:00 PM, "Cheng Hao" <[email protected]> wrote:
> In
>
sql/core/src/main/scala/org/apache/spark/sql/execution/basicOperators.scala:
>
> > @@ -97,6 +97,7 @@ case class Limit(limit: Int, child: SparkPlan)
> > // partition local limit -> exchange into one partition -> partition
local limit again
> >
> > override def output = child.output
> > + override def outputPartitioning = SinglePartition
>
> SinglePartition for LIMIT may cause performance issue for large number of
> records(in multiple partitions), do we really need to change this?
>
> â
> Reply to this email directly or view it on GitHub
> <https://github.com/apache/spark/pull/2262/files#r17096863>.
>
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