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https://issues.apache.org/jira/browse/SPARK-17774?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15544189#comment-15544189
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Shivaram Venkataraman commented on SPARK-17774:
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Could you explain why `head` is different from collect ? i.e. it seems like the
technical issues discussed in https://github.com/apache/spark/pull/11336 where
a column doesn't belong to one (or any) DataFrame still applies ?
> Add support for head on DataFrame Column
> ----------------------------------------
>
> Key: SPARK-17774
> URL: https://issues.apache.org/jira/browse/SPARK-17774
> Project: Spark
> Issue Type: Sub-task
> Components: SparkR
> Affects Versions: 2.0.0
> Reporter: Hossein Falaki
>
> There was a lot of discussion on SPARK-9325. To summarize the conversation on
> that ticket regardign {{collect}}
> * Pro: Ease of use and maximum compatibility with existing R API
> * Con: We do not want to increase maintenance cost by opening arbitrary API.
> With Spark's DataFrame API {{collect}} does not work on {{Column}} and there
> is no need for it to work in R.
> This ticket is strictly about {{head}}. I propose supporting {{head}} on
> {{Column}} because:
> 1. R users are already used to calling {{head(iris$Sepal.Length)}}. When they
> do that on SparkDataFrame they get an error. Not a good experience
> 2. Adding support for it does not require any change to the backend. It can
> be trivially done in R code.
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