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https://issues.apache.org/jira/browse/SPARK-17781?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15563193#comment-15563193
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Hossein Falaki commented on SPARK-17781:
----------------------------------------
I investigated the issue. The root cause is that Date (and Timestamp) types
convert to underlying representations when the are put in a list. To see it, do
following simple test in an R REPL:
{code}
> l <- lapply(1:2, function(x) { Sys.Date() })
> print(paste("list values", l))
[1] "list values 17084" "list values 17084"
{code}
Similar problem happens with POSIXlt and POSIXct types. Therefore in
{{worker.R}} when we call {{computeFunc(inputData)}} we are dealing with a list
that contains double values for date fields.
Right now it seems the safe way to work around it is avoiding Date and Time
types and instead use String. [~shivaram] and [~felixcheung] do you have any
ideas?
> datetime is serialized as double inside dapply()
> ------------------------------------------------
>
> Key: SPARK-17781
> URL: https://issues.apache.org/jira/browse/SPARK-17781
> Project: Spark
> Issue Type: Bug
> Components: SparkR
> Affects Versions: 2.0.0
> Reporter: Hossein Falaki
>
> When we ship a SparkDataFrame to workers for dapply family functions, inside
> the worker DateTime objects are serialized as double.
> To reproduce:
> {code}
> df <- createDataFrame(data.frame(id = 1:10, date = Sys.Date()))
> dapplyCollect(df, function(x) { return(x$date) })
> {code}
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