[GitHub] [arrow] westonpace commented on a diff in pull request #13150: ARROW-16549: [C++] Simplify AggregateNodeOptions aggregates/targets

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

westonpace commented on code in PR #13150:
URL: https://github.com/apache/arrow/pull/13150#discussion_r879775029


##########
r/R/query-engine.R:
##########
@@ -121,11 +119,13 @@ ExecPlan <- R6Class("ExecPlan",
             x
           })
         }
+        target_names <- names(.data$aggregations)
+        for (i in seq_len(length(target_names))) {
+          .data$aggregations[[i]][["name"]] <- .data$aggregations[[i]][["target"]] <- target_names[i]

Review Comment:
   For reference, the equivalent SQL is...
   
   ```
   SELECT function_1(target_1) as name_1, function_2(target_2) as name_2, ... FROM ... GROUP BY ...
   ```
   
   Each aggregate has (up to) three parts.  The C++ is changing from passing in three vectors of strings (which is error-prone) to passing in one vectors of structs where each item has up to three parts.



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