mopcup commented on code in PR #13934:
URL: https://github.com/apache/arrow/pull/13934#discussion_r978341369
##########
r/R/dplyr-distinct.R:
##########
@@ -35,8 +29,24 @@ distinct.arrow_dplyr_query <- function(.data, ..., .keep_all
= FALSE) {
# distinct() with no vars specified means distinct across all cols
.data <- dplyr::group_by(.data, !!!syms(names(.data)))
}
-
- out <- dplyr::summarize(.data, .groups = "drop")
+ if (isTRUE(.keep_all)) {
+ # (TODO) `.keep_all = TRUE` can return first row value, but this
implementation
+ # do not always return it because `hash_one` skips rows if they contain
null value.
+ # If group vars do not uniquely determine return values of each cols,
+ # the result will become different from the original.
+ # If NOT, this option may distroy data.
+ warning(".keep_all = TRUE currently not guarantee to take first row value
in each cols.")
Review Comment:
> Instead of raising a warning, can you rebase this PR
I did.
> and in
https://github.com/apache/arrow/blob/master/r/R/arrow-package.R#L53, leave the
note that ".keep_all = TRUE will keep one non-missing value for each column but
it may not be the 'first row'"
Please let me confirm. Is this fix correct?
```
diff --git a/r/R/arrow-package.R b/r/R/arrow-package.R
index e6b3f481e..9c003969d 100644
--- a/r/R/arrow-package.R
+++ b/r/R/arrow-package.R
@@ -50,7 +50,7 @@ supported_dplyr_methods <- list(
relocate = NULL,
compute = NULL,
collapse = NULL,
- distinct = NULL,
+ distinct = ".keep_all = TRUE will keep one non-missing value for each
column but it may not be the 'first row'",
left_join = NULL,
right_join = NULL,
inner_join = NULL,
```
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