[GitHub] [arrow-adbc] paleolimbot commented on issue #1005: r/adbcsqlite: int type conversion to R

["paleolimbot (via GitHub)" <gi...@apache.org>]

paleolimbot commented on issue #1005:
URL: https://github.com/apache/arrow-adbc/issues/1005#issuecomment-1701714557

   We chatted a bit offline about this, but this happens because nanoarrow's default conversion from Arrow's `int64` type is an R `double`. This is potentially a bad choice but was one that I did because (1) you will always get the same answer for `nanoarrow_infer_ptype(some_array_of_integers)`, which matters in the preallocate + fill pattern where you allocate before you know exactly what data you have and (2) because using `bit64::integer64()` requires a dependency (`classInt`) that is a bit heavy and requires a Fortran compiler.
   
   At least in nanoarrow (not in arrow), you can always tell it what R vector type you want back:
   
   ``` r
   library(nanoarrow)
   
   int64_array <- as_nanoarrow_array(
     data.frame(x = 1:5),
     schema = na_struct(list(x = na_int64()))
   )
   
   str(convert_array_stream(basic_array_stream(list(int64_array))))
   #> 'data.frame':    5 obs. of  1 variable:
   #>  $ x: num  1 2 3 4 5
   
   str(
     convert_array_stream(
       basic_array_stream(list(int64_array)),
       to = data.frame(x = integer())
     )
   )
   #> 'data.frame':    5 obs. of  1 variable:
   #>  $ x: int  1 2 3 4 5
   ```
   
   I'm not keen to implement a list of options in nanoarrow or adbcdrivermanager although I get how it may be helpful to temporarily replace the default behaviour of `nanoarrow_infer_ptype()` to give something that is safer (e.g., `integer64()`) or more practical (e.g., `integer()`).


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