wjones127 commented on code in PR #14286:
URL: https://github.com/apache/arrow/pull/14286#discussion_r995138972
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r/R/query-engine.R:
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@@ -384,3 +397,65 @@ needs_projection <- function(projection, schema) {
!identical(field_names, names(projection)) || # Any fields are renamed
!identical(field_names, names(schema)) # The fields are reordered
}
+
+#' Create projection needed to coalesce join keys after a full outer join
+#'
+#' @examples
+#' test_join <- list(
+#' type = JoinType$FULL_OUTER,
+#' right_data = arrow_table(x = 1, y = 2, z = "x"),
+#' by = c("x", "y"),
+#' suffix = c(".x", ".y"),
+#' keep = FALSE
+#' )
+#' post_join_projection(c("value", "x", "y", "z"), test_join)
+#'
+#' @noRd
+post_join_projection <- function(left_names, join_config) {
+ # Need to coalesce the key columns
+ right_names <- names(join_config$right_data)
+ # Collect mapping of which columns on left need to be coalesced with which
+ # column on the right side.
+ coalesce_targets <- data.frame(
Review Comment:
I'm not sure how that would work. If there's something like a Python
dictionary that can represent `Dict[int, int]` that would be nice. But it would
only eliminate one line I think.
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