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https://issues.apache.org/jira/browse/ARROW-12693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17568225#comment-17568225
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Sam Albers commented on ARROW-12693:
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> Well, the original issue reporter seemed to expect that it would work ;)
So foolish he was.
> feature request to support $ on query objects
I wasn't able to find a specific ticket for that. I can create one though as I
think it might something worth exploring.
> [R] add unique() methods for ArrowTabular, datasets
> ---------------------------------------------------
>
> Key: ARROW-12693
> URL: https://issues.apache.org/jira/browse/ARROW-12693
> Project: Apache Arrow
> Issue Type: Improvement
> Components: R
> Reporter: Sam Albers
> Priority: Minor
> Labels: pull-request-available
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> I am trying to see if I can leverage `unique` on a Dataset object. Imagining
> a much big dataset, I am trying to get away from this expensive pattern:
> {code:java}
> Dataset %>%
> pull(col) %>%
> unique(){code}
> However when I try the option below it is not working quite how I'd expect.
> I'm actually not able to get any working (e.g. `arrow_mean`) so maybe I am
> misunderstanding how these are meant to work.
> {code:java}
> library(arrow, warn.conflicts = FALSE)
> library(dplyr, warn.conflicts = FALSE)
> dir.create("iris")
> iris %>%
> group_by(Species) %>%
> write_dataset("iris")
> ds <- open_dataset("iris")
> ds %>%
> mutate(unique = arrow_unique(Species)) %>%
> collect()
> #> Error: Invalid: ExecuteScalarExpression cannot Execute non-scalar
> expression unique("setosa")
> ds %>%
> mutate(unique = arrow_unique(Petal.Width)) %>%
> collect()
> #> Error: Invalid: ExecuteScalarExpression cannot Execute non-scalar
> expression {Sepal.Length=Sepal.Length, Sepal.Width=Sepal.Width,
> Petal.Length=Petal.Length, Petal.Width=Petal.Width, Species="setosa",
> unique=unique(Petal.Width)}
> call_function("unique", ds, "Species")
> #> Error: Argument 1 is of class FileSystemDataset but it must be one of
> "Array", "ChunkedArray", "RecordBatch", "Table", or "Scalar"
> call_function("unique", ds, "Petal.Width")
> #> Error: Argument 1 is of class FileSystemDataset but it must be one of
> "Array", "ChunkedArray", "RecordBatch", "Table", or "Scalar"
> call_function("mean", ds, "Petal.Width")
> #> Error: Argument 1 is of class FileSystemDataset but it must be one of
> "Array", "ChunkedArray", "RecordBatch", "Table", or "Scalar"
> sessioninfo::session_info()
> #> - Session info
> ---------------------------------------------------------------
> #> setting value
> #> version R version 4.0.5 (2021-03-31)
> #> os Windows 10 x64
> #> system x86_64, mingw32
> #> ui RTerm
> #> language (EN)
> #> collate English_Canada.1252
> #> ctype English_Canada.1252
> #> tz America/Los_Angeles
> #> date 2021-05-07
> #>
> #> - Packages
> -------------------------------------------------------------------
> #> package * version date lib source
> #> arrow * 4.0.0 2021-04-27 [1] CRAN (R 4.0.5)
> #> assertthat 0.2.1 2019-03-21 [1] CRAN (R 4.0.0)
> #> backports 1.2.1 2020-12-09 [1] CRAN (R 4.0.3)
> #> bit 4.0.4 2020-08-04 [1] CRAN (R 4.0.2)
> #> bit64 4.0.5 2020-08-30 [1] CRAN (R 4.0.2)
> #> cli 2.5.0 2021-04-26 [1] CRAN (R 4.0.5)
> #> crayon 1.4.1 2021-02-08 [1] CRAN (R 4.0.3)
> #> DBI 1.1.1 2021-01-15 [1] CRAN (R 4.0.3)
> #> digest 0.6.27 2020-10-24 [1] CRAN (R 4.0.3)
> #> dplyr * 1.0.5 2021-03-05 [1] CRAN (R 4.0.5)
> #> ellipsis 0.3.2 2021-04-29 [1] CRAN (R 4.0.5)
> #> evaluate 0.14 2019-05-28 [1] CRAN (R 4.0.0)
> #> fansi 0.4.2 2021-01-15 [1] CRAN (R 4.0.3)
> #> fs 1.5.0 2020-07-31 [1] CRAN (R 4.0.2)
> #> generics 0.1.0 2020-10-31 [1] CRAN (R 4.0.3)
> #> glue 1.4.2 2020-08-27 [1] CRAN (R 4.0.2)
> #> highr 0.9 2021-04-16 [1] CRAN (R 4.0.4)
> #> htmltools 0.5.1.1 2021-01-22 [1] CRAN (R 4.0.3)
> #> knitr 1.33 2021-04-24 [1] CRAN (R 4.0.5)
> #> lifecycle 1.0.0 2021-02-15 [1] CRAN (R 4.0.4)
> #> magrittr 2.0.1 2020-11-17 [1] CRAN (R 4.0.3)
> #> pillar 1.6.0 2021-04-13 [1] CRAN (R 4.0.5)
> #> pkgconfig 2.0.3 2019-09-22 [1] CRAN (R 4.0.0)
> #> purrr 0.3.4 2020-04-17 [1] CRAN (R 4.0.0)
> #> R.cache 0.15.0 2021-04-30 [1] CRAN (R 4.0.5)
> #> R.methodsS3 1.8.1 2020-08-26 [1] CRAN (R 4.0.2)
> #> R.oo 1.24.0 2020-08-26 [1] CRAN (R 4.0.2)
> #> R.utils 2.10.1 2020-08-26 [1] CRAN (R 4.0.2)
> #> R6 2.5.0 2020-10-28 [1] CRAN (R 4.0.3)
> #> reprex 2.0.0 2021-04-02 [1] CRAN (R 4.0.5)
> #> rlang 0.4.10 2020-12-30 [1] CRAN (R 4.0.3)
> #> rmarkdown 2.7 2021-02-19 [1] CRAN (R 4.0.4)
> #> sessioninfo 1.1.1 2018-11-05 [1] CRAN (R 4.0.0)
> #> stringi 1.5.3 2020-09-09 [1] CRAN (R 4.0.2)
> #> stringr 1.4.0 2019-02-10 [1] CRAN (R 4.0.2)
> #> styler 1.4.1 2021-03-30 [1] CRAN (R 4.0.4)
> #> tibble 3.1.1 2021-04-18 [1] CRAN (R 4.1.0)
> #> tidyselect 1.1.1 2021-04-30 [1] CRAN (R 4.0.5)
> #> utf8 1.2.1 2021-03-12 [1] CRAN (R 4.0.5)
> #> vctrs 0.3.8 2021-04-29 [1] CRAN (R 4.0.5)
> #> withr 2.4.2 2021-04-18 [1] CRAN (R 4.0.4)
> #> xfun 0.22 2021-03-11 [1] CRAN (R 4.0.4)
> #> yaml 2.2.1 2020-02-01 [1] CRAN (R 4.0.0)
> #>
> #> [1] C:/Users/salbers/R/win-library/4.0
> #> [2] C:/Program Files/R/R-4.0.5/library
> {code}
> {color:#172b4d}I am opening this a) because others may have run into the same
> issue and b) just in case this is actually a bug. Feel free to close
> immediately if this isn't the way these are supposed to work. {color}
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