[GitHub] [arrow] ianmcook commented on a change in pull request #10191: ARROW-12731: [R] Use InMemoryDataset for Table/RecordBatch in dplyr code

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

ianmcook commented on a change in pull request #10191:
URL: https://github.com/apache/arrow/pull/10191#discussion_r631530324



##########
File path: r/R/dplyr.R
##########
@@ -58,40 +63,36 @@ arrow_dplyr_query <- function(.data) {
   )
 }
 
+make_field_refs <- function(field_names) {
+  set_names(lapply(field_names, Expression$field_ref), field_names)
+}
+
 #' @export
 print.arrow_dplyr_query <- function(x, ...) {
   schm <- x$.data$schema
-  cols <- get_field_names(x)
-  # If cols are expressions, they won't be in the schema and will be "" in cols
-  fields <- map_chr(cols, function(name) {
+  fields <- map_chr(x$selected_columns, function(expr) {
+    name <- expr$field_name
     if (nzchar(name)) {
       schm$GetFieldByName(name)$ToString()
     } else {
+      # It's "" because this is not a field_ref, it's a more complex expression
       "expr"

Review comment:
       Would this also enable ARROW-12291?




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