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https://issues.apache.org/jira/browse/SPARK-6830?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15033437#comment-15033437
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Sun Rui commented on SPARK-6830:
--------------------------------

Even in query planner, there are some cases that the planner can not know the 
result is deterministic or not? for example, if the source file for a DataFrame 
may change on time, does the planner know this? But the user knows that the 
source will change or not.

> Memoize frequently queried vals in RDD, such as numPartitions, count etc.
> -------------------------------------------------------------------------
>
>                 Key: SPARK-6830
>                 URL: https://issues.apache.org/jira/browse/SPARK-6830
>             Project: Spark
>          Issue Type: Improvement
>          Components: SparkR
>            Reporter: Shivaram Venkataraman
>            Priority: Minor
>              Labels: Starter
>
> We should memoize frequently queried vals in RDD, such as numPartitions, 
> count etc.
> While using SparkR in RStudio, the `count` function seems to be called 
> frequently by the IDE – I think this is to show some stats about variables in 
> the workspace etc. but this is not great in SparkR as we trigger a job every 
> time count is called.
> Memoization would help in this case, but we should also see if there is some 
> better way to interact with RStudio.



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