GitHub user titicaca opened a pull request:
https://github.com/apache/spark/pull/16689
SPARK-19342 bug fixed in collect method for collecting timestamp column
## What changes were proposed in this pull request?
Fix a bug in collect method for collecting timestamp column, the bug can be
reproduced as shown in the following codes and outputs:
```
library(SparkR)
sparkR.session(master = "local")
df <- data.frame(col1 = c(0, 1, 2),
col2 = c(as.POSIXct("2017-01-01 00:00:01"), NA,
as.POSIXct("2017-01-01 12:00:01")))
sdf1 <- createDataFrame(df)
print(dtypes(sdf1))
df1 <- collect(sdf1)
print(lapply(df1, class))
sdf2 <- filter(sdf1, "col1 > 0")
print(dtypes(sdf2))
df2 <- collect(sdf2)
print(lapply(df2, class))
```
As we can see from the printed output, the column type of col2 in df2 is
converted to numeric unexpectedly, when NA exists at the top of the column.
This is caused by method `do.call(c, list)`, if we convert a list, i.e.
`do.call(c, list(NA, as.POSIXct("2017-01-01 12:00:01"))`, the class of the
result is numeric instead of POSIXct.
Therefore, we need to cast the data type of the vector explicitly.
## How was this patch tested?
The patch can be tested manually with the same code above.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/titicaca/spark sparkr-dev
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/16689.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #16689
----
commit a51c2eb54ca672ad63495d0709bd3ae7b254bd14
Author: titicaca <fangzhou.y...@hotmail.com>
Date: 2017-01-24T06:24:47Z
SPARK-19342 bug fixed in collect method for collecting timestamp column
----
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