[jira] [Commented] (SPARK-4824) Join should use `Iterator` rather than `Iterable`

["Apache Spark (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-4824?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14242056#comment-14242056 ] 

Apache Spark commented on SPARK-4824:
-------------------------------------

User 'zsxwing' has created a pull request for this issue:
https://github.com/apache/spark/pull/3671

> Join should use `Iterator` rather than `Iterable`
> -------------------------------------------------
>
>                 Key: SPARK-4824
>                 URL: https://issues.apache.org/jira/browse/SPARK-4824
>             Project: Spark
>          Issue Type: Bug
>          Components: Spark Core
>            Reporter: Shixiong Zhu
>
> In Scala, `map` and `flatMap` of `Iterable` will copy the contents of `Iterable` to a new `Seq`. Such as,
> {code}
>   val iterable = Seq(1, 2, 3).map(v => {
>     println(v)
>     v
>   })
>   println("Iterable map done")
>   val iterator = Seq(1, 2, 3).iterator.map(v => {
>     println(v)
>     v
>   })
>   println("Iterator map done")
> {code}
> outputed
> {code}
> 1
> 2
> 3
> Iterable map done
> Iterator map done
> {code}
> So we should use 'iterator' to reduce memory consumed by join.
> Found by [~johannes.simon]



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