[ARROW-18241] [C++] Add cast option to return null for values that can't convert

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: C++, R
• External issue URL: https://github.com/apache/arrow/issues/20486
• Assignee: Unassigned
• Reporter: Lucas Mation
• Created: 03/Nov/22 16:16
• Updated: 11/Jan/23 11:59

Description

I am importing a dataset with arrow, and then converting variable types. But I got an error message because the `arrow` implementation of `as.integer` can't handle empty strings (which is legal in base R). Is this a bug?

#In R
'' %>% as.integer()

[1] NA

 

#in arrow

q <- data.table(x=c('','1','2'))
q %>% write_dataset('q')
q2 <- 'q' %>% open_dataset %>% mutate(x=as.integer(x)) %>% collect

Error in `collect()`:
! Invalid: Failed to parse string: '' as a scalar of type int32
Run `rlang::last_error()` to see where the error occurred.

Update: tryed to preprocess x with `ifelse` but it also did not work.

'q' %>% open_dataset %>% mutate(x= ifelse(x=='',NA,x)) %>% mutate(x=as.integer(x)) %>% collect
Error in `collect()`:
! NotImplemented: Function 'if_else' has no kernel matching input types (bool, bool, string)
Run `rlang::last_error()` to see where the error occurred.

Issue Links

• is duplicated by: ARROW-18267 [R] Possible bug in Handling Blank Conversion to Missing Value