[ARROW-13588] [R] Empty character attributes not stored

• Type: Bug
• Status: Open
• Priority: Critical
• Resolution: Unresolved
• Affects Version/s: 5.0.0
• Component/s: R
• Labels: attributes feather
• Environment: Ubuntu 20.04 R 4.1 release
• External issue URL: https://github.com/apache/arrow/issues/29233

Language

English

• Assignee: Unassigned
• Reporter: Charlie Gao
• Created: 09/Aug/21 16:14
• Updated: 11/Jan/23 08:34

Description

Date-times in the POSIXct format have a 'tzone' attribute that by default is set to "", an empty character vector (not NULL) when created.

This however is not stored in the Arrow feather file. When the file is read back, the original and restored dataframes are not identical as per the below reprex.

I am thinking that this should not be the intention? My workaround at the moment is making a check when reading back to write the empty string if the tzone attribute does not exist.

Just to confirm, the attribute is stored correctly when it is not empty.

Thanks.

``` r
 dates <- as.POSIXct(c("2020-01-01", "2020-01-02", "2020-01-02"))
 attributes(dates)
 #> $class
 #> [1] "POSIXct" "POSIXt" 
 #> 
 #> $tzone
 #> [1] ""

 values <- c(1:3)
 original <- data.frame(dates, values)
 original
 #> dates values
 #> 1 2020-01-01 1
 #> 2 2020-01-02 2
 #> 3 2020-01-02 3

tempfile <- tempfile()
arrow::write_feather(original, tempfile)

restored <- arrow::read_feather(tempfile)

identical(original, restored)
 #> [1] FALSE

 waldo::compare(original, restored)
 #> `attr(old$dates, 'tzone')` is a character vector ('')
 #> `attr(new$dates, 'tzone')` is absent

unlink(tempfile)
 ```