[jira] [Commented] (ARROW-17738) [R] dplyr::compute should convert from grouped arrow_dplyr_query to arrow Table

["Neal Richardson (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-17738?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17606157#comment-17606157 ] 

Neal Richardson commented on ARROW-17738:
-----------------------------------------

They are evaluated and converted to Tables, but then if there are groups, group_by is called on the Table, which results in an arrow_dplyr_query object containing the Table. So, yes, this was intentional. Do you have a use case where this is a problem?

> [R] dplyr::compute should convert from grouped arrow_dplyr_query to arrow Table
> -------------------------------------------------------------------------------
>
>                 Key: ARROW-17738
>                 URL: https://issues.apache.org/jira/browse/ARROW-17738
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: R
>    Affects Versions: 9.0.0
>            Reporter: SHIMA Tatsuya
>            Assignee: SHIMA Tatsuya
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> It is expected that {{dplyr::compute()}} will perform the calculation on the arrow dplyr query and convert it to a Table, but it does not seem to work correctly for grouped arrow dplyr queries and does not result in a Table.
> {code:r}
> mtcars |> arrow::arrow_table() |> dplyr::group_by(cyl) |> dplyr::compute() |> class()
> #> [1] "arrow_dplyr_query"
> mtcars |> arrow::arrow_table() |> dplyr::group_by(cyl) |> dplyr::ungroup() |> dplyr::compute() |> class()
> #> [1] "Table"        "ArrowTabular" "ArrowObject"  "R6"
> {code}
> {{as_arrow_table()}} works fine.
> {code:r}
> mtcars |> arrow::arrow_table() |> dplyr::group_by(cyl) |> class()
> #> [1] "arrow_dplyr_query"
> mtcars |> arrow::arrow_table() |> dplyr::group_by(cyl) |> dplyr::compute() |> class()
> #> [1] "arrow_dplyr_query"
> mtcars |> arrow::arrow_table() |> dplyr::group_by(cyl) |> dplyr::collect(FALSE) |> class()
> #> [1] "arrow_dplyr_query"
> mtcars |> arrow::arrow_table() |> dplyr::group_by(cyl) |> arrow::as_arrow_table() |> class()
> #> [1] "Table"        "ArrowTabular" "ArrowObject"  "R6"
> {code}
> It seems to revert to arrow dplyr query in the following line.
> [https://github.com/apache/arrow/blob/7cfdfbb0d5472f8f8893398b51042a3ca1dd0adf/r/R/dplyr-collect.R#L73-L75]
>  



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