jonkeane commented on code in PR #51392:
URL: https://github.com/apache/arrow/pull/51392#discussion_r4071322961
##########
r/vignettes/dataset.Rmd:
##########
@@ -308,6 +308,23 @@ in order to declare the types of the virtual columns that
define the partitions.
This would be useful, in the NYC taxi data example, if you wanted to keep
`month` as a string instead of an integer.
+### Record which file each row came from
+
+Partitioning only recovers information encoded in directory names. If you need
+the full path of the file each row was read from, use `add_filename()` inside a
+query on the Dataset:
+
+```r
+ds |>
+ mutate(file = add_filename()) |>
+ collect()
+```
+
+This is handy when you have opened a single partition directory directly (for
+example, `open_dataset("nyc-taxi/year=2015")`), since in that case the
partition
+columns above that directory (here, `year`) are not inferred and you may want
to
+recover them from the path. See `?add_filename` for details and limitations.
Review Comment:
Same thing here? Can we have roxygen "just" link this to the thing?
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