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From "Hossein Falaki (JIRA)" <>
Subject [jira] [Commented] (SPARK-17774) Add support for head on DataFrame Column
Date Wed, 05 Oct 2016 20:53:20 GMT


Hossein Falaki commented on SPARK-17774:

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:
>             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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