[jira] [Created] (ARROW-14036) [R] Binding for n_distinct() with no grouping

["Ian Cook (Jira)" <ji...@apache.org>]

Ian Cook created ARROW-14036:
--------------------------------

             Summary: [R] Binding for n_distinct() with no grouping
                 Key: ARROW-14036
                 URL: https://issues.apache.org/jira/browse/ARROW-14036
             Project: Apache Arrow
          Issue Type: New Feature
          Components: R
            Reporter: Ian Cook
             Fix For: 6.0.0


ARROW-13620 added a binding for {{n_distinct()}} but it only works for _grouped_ aggregation, not whole-table aggregation. 

This works:
{code:java}
Table$create(starwars) %>%
  group_by(homeworld) %>%
  summarise(n_distinct(species)) %>%
  collect(){code}
but this errors:
{code:java}
Table$create(starwars) %>%
  summarise(n_distinct(species)) %>%
  collect()

#> Error: Key error: No function registered with name: count_distinct{code}
Once we have a non-hash {{count_distinct}} aggregate kernel in the C++ library (ARROW-14035) we should bind the options for it in the R package and add a test.



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