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

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

     [ https://issues.apache.org/jira/browse/ARROW-14036?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ian Cook reassigned ARROW-14036:
--------------------------------

    Assignee: Ian Cook

> [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
>            Assignee: Ian Cook
>            Priority: Critical
>              Labels: kernel
>             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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