[jira] [Created] (ARROW-18006) [R] integer coercion on parition variables

["Carl Boettiger (Jira)" <ji...@apache.org>]

Carl Boettiger created ARROW-18006:
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             Summary: [R] integer coercion on parition variables
                 Key: ARROW-18006
                 URL: https://issues.apache.org/jira/browse/ARROW-18006
             Project: Apache Arrow
          Issue Type: Bug
          Components: R
    Affects Versions: 9.0.0
            Reporter: Carl Boettiger


If we partition on a character-string column that is "integer-like", arrow assumes the resulting partition variable is an integer.  This is particularly surprising because in most other cases, making a column a partition variable coerces it to a character (makes sense, path names are strings), but in this case we have the opposite coercion where a string becomes an integer.  Consider this reprex:


{code:java}
library(arrow)f <- tempfile()
df <- data.frame(x = c("00", "06", "18"))
df |> write_dataset(f, partitioning = "x")
open_dataset(f) # x is now an integer{code}
{code:java}
## fails
open_dataset(f) |> filter(x == "00")
 {code}
changing this behavior could break existing code I think, so maybe this shouldn't be considered a bug, but I think it merits discussion. 

(For instance, we often see large datasets, e.g. from NOAA csv etc, that use zero-padded integers in path names to indicate file-specific metadata.  One side effect of the type-coercion is that it also strips  the zero-padding)



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