[GitHub] [arrow] eitsupi commented on a diff in pull request #14175: ARROW-17737: [R] Continue to retain grouping metadata even if ungroup arrow dplyr query

[GitBox <gi...@apache.org>]

eitsupi commented on code in PR #14175:
URL: https://github.com/apache/arrow/pull/14175#discussion_r975560514


##########
r/R/dplyr-collect.R:
##########
@@ -60,20 +62,23 @@ restore_dplyr_features <- function(df, query) {
   # An arrow_dplyr_query holds some attributes that Arrow doesn't know about
   # After calling collect(), make sure these features are carried over
 
-  if (length(query$group_by_vars) > 0) {
+  if (is.data.frame(df)) {
     # Preserve groupings, if present
-    if (is.data.frame(df)) {
+    if (length(query$group_by_vars) > 0) {
       df <- dplyr::grouped_df(
         df,
         dplyr::group_vars(query),
         drop = dplyr::group_by_drop_default(query)
       )
+    }
+  } else {
+    # This is a Table, via compute() or collect(as_data_frame = FALSE)
+    if (length(query$group_by_vars) > 0) {
+      gv <- query$group_by_vars
     } else {
-      # This is a Table, via compute() or collect(as_data_frame = FALSE)
-      df <- as_adq(df)
-      df$group_by_vars <- query$group_by_vars
-      df$drop_empty_groups <- query$drop_empty_groups
+      gv <- NULL

Review Comment:
   Perhaps `restore_dplyr_features` should make sure that `df` is not grouped.
   If it is guaranteed that `df` is not grouped, this case will be unnecessary.



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