ianmcook commented on code in PR #33917:
URL: https://github.com/apache/arrow/pull/33917#discussion_r1103101067
##########
r/R/dplyr-summarize.R:
##########
@@ -322,15 +301,71 @@ arrow_eval_or_stop <- function(expr, mask) {
out
}
+# This function returns a list of expressions which is used to project the data
+# before an aggregation. This list includes the fields used in the aggregation
+# expressions (the "targets") and the group fields. The names of the returned
+# list are used to ensure that the projection node is wired up correctly to the
+# aggregation node.
summarize_projection <- function(.data) {
c(
- map(.data$aggregations, ~ .$data),
+ unlist(unname(imap(
+ .data$aggregations,
+ ~set_names(
+ .x$data,
+ aggregate_target_names(.x$data, .y)
+ )
+ ))),
.data$selected_columns[.data$group_by_vars]
)
}
+# This function determines what names to give to the fields used in an
+# aggregation expression (the "targets"). When an aggregate function takes 2 or
+# more fields as targets, this function gives the fields unique names by
+# appending `..1`, `..2`, etc. When an aggregate function is nullary, this
+# function returns a zero-length character vector.
+aggregate_target_names <- function(data, name) {
+ if (length(data) > 1) {
+ paste(name, seq_along(data), sep = "..")
+ } else if (length(data) > 0) {
+ name
+ } else {
+ character(0)
+ }
+}
+
+# This function returns a named list of the data types of the aggregate columns
+# returned by an aggregation
+aggregate_types <- function(.data, hash, schema = NULL) {
Review Comment:
The code in `dplyr-collect.R` passes `old_schm` to this function. That's how
it worked before and I didn't want to change in for fear of breaking it.
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