ARROW-15701 [R] month() should allow integer inputs

[dragosmg]

Once this PR is merge the {arrow} binding for month() will be able to accept integer inputs. This also impact the semester() which now will be able to extract semesters from integer inputs.

library(lubridate)
library(dplyr)
library(arrow)

df <- tibble(
  month_as_int = 1:12
)

df %>% 
  mutate(m = month(month_as_int),
         s = semester(month_as_int))
#> # A tibble: 12 × 3
#>    month_as_int     m     s
#>           <int> <int> <int>
#>  1            1     1     1
#>  2            2     2     1
#>  3            3     3     1
#>  4            4     4     1
#>  5            5     5     1
#>  6            6     6     1
#>  7            7     7     2
#>  8            8     8     2
#>  9            9     9     2
#> 10           10    10     2
#> 11           11    11     2
#> 12           12    12     2

df %>% 
  arrow_table() %>% 
  mutate(m = month(month_as_int),
         s = semester(month_as_int)) %>% 
  collect()
#> # A tibble: 12 × 3
#>    month_as_int     m     s
#>           <int> <int> <int>
#>  1            1     1     1
#>  2            2     2     1
#>  3            3     3     1
#>  4            4     4     1
#>  5            5     5     1
#>  6            6     6     1
#>  7            7     7     2
#>  8            8     8     2
#>  9            9     9     2
#> 10           10    10     2
#> 11           11    11     2
#> 12           12    12     2

^{Created on 2022-03-02 by the reprex package (v2.0.1)}

[github-actions]

https://issues.apache.org/jira/browse/ARROW-15701

[dragosmg]

This is a cheeky implementation, but it works. 😄

[jonkeane]

We could actually short-circuit here and return the expression with simply if_else when label = FALSE, since that will return an integer itself, yeah?

I agree that this is a little bit unorthodox, but I think it works. An alternative would be to put this value into a date string with a call to the paste binding and then doing strptime on that. Both aren't super ideal — but I suspect that this integer multiplication is going to be more performant (though if we are basing a decision on that, we probably should measure it!).

[dragosmg]

I haven't done any benchmarking yet.

[jonkeane]

This is looking good — a few comments about the structure of the function body.

Also, there's at least one call to Expression$create() that probably could be build_expr(), what do you think?

[jonkeane]

We could actually short-circuit here and return the expression with simply if_else when label = FALSE, since that will return an integer itself, yeah?

I agree that this is a little bit unorthodox, but I think it works. An alternative would be to put this value into a date string with a call to the paste binding and then doing strptime on that. Both aren't super ideal — but I suspect that this integer multiplication is going to be more performant (though if we are basing a decision on that, we probably should measure it!).

[jonkeane]

Two very minor, more stylistic nit-picky comments that you can take or leave

[ursabot]

Benchmark runs are scheduled for baseline = a76794c and contender = 1b77e6d. 1b77e6d is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Finished ⬇️0.0% ⬆️0.0%] ec2-t3-xlarge-us-east-2
[Finished ⬇️0.25% ⬆️0.0%] test-mac-arm
[Finished ⬇️0.0% ⬆️0.0%] ursa-i9-9960x
[Finished ⬇️0.81% ⬆️0.0%] ursa-thinkcentre-m75q
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java