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https://issues.apache.org/jira/browse/SPARK-17774?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15549913#comment-15549913
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Hossein Falaki commented on SPARK-17774:
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I strongly feel {{head}} should work, but I don't have as strong opinion about
{{collect}}, although it would be nice if that worked too.
On returning error vs. empty vector, I think returning error is safer because
it will not cause silent problems.
> 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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