Support integer date and time classes from data.table

[svraka]

Describe the enhancement requested

The data.table package introduces integer based date and time-of-day classes, IDate, and ITime. Besides lower storage/memory cost, they offer faster sorting and grouping. It would be useful if Arrow fully supported these classes.

As IDate inherits from Date, Arrow correctly converts it to date32 but there is no way to control which R type date32 is converted to.

library(arrow)
library(data.table)

id <- as.IDate(Sys.Date())
str(id)
#>  IDate[1:1], format: "2024-09-19"
chunked_array(id)
#> ChunkedArray
#> <date32[day]>
#> [
#>   [
#>     2024-09-19
#>   ]
#> ]
str(as.vector(chunked_array(id)))
#>  Date[1:1], format: "2024-09-19"

ITime can be correctly round-tripped, if I’m not mistaken this is because Arrow preserves metadata.

it <- as.ITime(Sys.time())
str(it)
#>  'ITime' int 17:27:28
chunked_array(it)
#> ChunkedArray
#> <character(0)>
#> [
#>   [
#>     62848
#>   ]
#> ]
str(as.vector(chunked_array(it)))
#>  'ITime' int 17:27:28

Although this works, converting to time32 would improve interoperability with other languages. data.table users would need some way to control how time32 is converted back is this case too.

^{Created on 2024-09-19 with reprex v2.1.1}

Session info

sessioninfo::session_info()
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#> ────────────────────────────────────────────────────────────────────────────────────────────────────

Component(s)

R